HashSet<T> Class

Definition

Namespace:

System.Collections.Generic

Assembly:

System.Collections.dll

Source:

HashSet.cs

Represents a set of values.

generic <typename T>
public ref class HashSet : System::Collections::Generic::ICollection<T>, System::Collections::Generic::IEnumerable<T>, System::Collections::Generic::IReadOnlyCollection<T>, System::Collections::Generic::IReadOnlySet<T>, System::Collections::Generic::ISet<T>, System::Runtime::Serialization::IDeserializationCallback, System::Runtime::Serialization::ISerializable

public class HashSet<T> : System.Collections.Generic.ICollection<T>, System.Collections.Generic.IEnumerable<T>, System.Collections.Generic.IReadOnlyCollection<T>, System.Collections.Generic.IReadOnlySet<T>, System.Collections.Generic.ISet<T>, System.Runtime.Serialization.IDeserializationCallback, System.Runtime.Serialization.ISerializable

type HashSet<'T> = class
    interface ICollection<'T>
    interface seq<'T>
    interface IEnumerable
    interface IReadOnlyCollection<'T>
    interface ISet<'T>
    interface IReadOnlySet<'T>
    interface IDeserializationCallback
    interface ISerializable

Public Class HashSet(Of T)
Implements ICollection(Of T), IDeserializationCallback, IEnumerable(Of T), IReadOnlyCollection(Of T), IReadOnlySet(Of T), ISerializable, ISet(Of T)

Type Parameters

T

The type of elements in the hash set.

Inheritance

Object

HashSet<T>

Implements

ICollection<T> IEnumerable<T> IReadOnlyCollection<T> ISet<T> IEnumerable IReadOnlySet<T> IDeserializationCallback ISerializable

Examples

The following example demonstrates how to merge two disparate sets. This example creates two HashSet<T> objects and populates them with even and odd numbers, respectively. A third HashSet<T> object is created from the set that contains the even numbers. The example then calls the UnionWith method, which adds the odd number set to the third set.

HashSet<int> evenNumbers = new HashSet<int>();
HashSet<int> oddNumbers = new HashSet<int>();

for (int i = 0; i < 5; i++)
{
    // Populate numbers with just even numbers.
    evenNumbers.Add(i * 2);

    // Populate oddNumbers with just odd numbers.
    oddNumbers.Add((i * 2) + 1);
}

Console.Write("evenNumbers contains {0} elements: ", evenNumbers.Count);
DisplaySet(evenNumbers);

Console.Write("oddNumbers contains {0} elements: ", oddNumbers.Count);
DisplaySet(oddNumbers);

// Create a new HashSet populated with even numbers.
HashSet<int> numbers = new HashSet<int>(evenNumbers);
Console.WriteLine("numbers UnionWith oddNumbers...");
numbers.UnionWith(oddNumbers);

Console.Write("numbers contains {0} elements: ", numbers.Count);
DisplaySet(numbers);

void DisplaySet(HashSet<int> collection)
{
    Console.Write("{");
    foreach (int i in collection)
    {
        Console.Write(" {0}", i);
    }
    Console.WriteLine(" }");
}

/* This example produces output similar to the following:
* evenNumbers contains 5 elements: { 0 2 4 6 8 }
* oddNumbers contains 5 elements: { 1 3 5 7 9 }
* numbers UnionWith oddNumbers...
* numbers contains 10 elements: { 0 2 4 6 8 1 3 5 7 9 }
*/

let displaySet (collection: HashSet<int>) =
    printf "{"

    for i in collection do
        printf $" {i}"

    printfn " }"

let evenNumbers = HashSet<int>()
let oddNumbers = HashSet<int>()

for i = 0 to 4 do
    // Populate numbers with just even numbers.
    evenNumbers.Add(i * 2) |> ignore

    // Populate oddNumbers with just odd numbers.
    oddNumbers.Add(i * 2 + 1) |> ignore

printf $"evenNumbers contains {evenNumbers.Count} elements: "
displaySet evenNumbers

printf $"oddNumbers contains {oddNumbers.Count} elements: "
displaySet oddNumbers

// Create a new HashSet populated with even numbers.
let numbers = HashSet<int> evenNumbers
printfn "numbers UnionWith oddNumbers..."
numbers.UnionWith oddNumbers

printf $"numbers contains {numbers.Count} elements: "
displaySet numbers
// This example produces output similar to the following:
//    evenNumbers contains 5 elements: { 0 2 4 6 8 }
//    oddNumbers contains 5 elements: { 1 3 5 7 9 }
//    numbers UnionWith oddNumbers...
//    numbers contains 10 elements: { 0 2 4 6 8 1 3 5 7 9 }

Imports System.Collections.Generic

Class Program

    Shared Sub Main()

        Dim evenNumbers As HashSet(Of Integer) = New HashSet(Of Integer)()
        Dim oddNumbers As HashSet(Of Integer) = New HashSet(Of Integer)()

        For i As Integer = 0 To 4

            ' Populate evenNumbers with only even numbers.
            evenNumbers.Add(i * 2)

            ' Populate oddNumbers with only odd numbers.
            oddNumbers.Add((i * 2) + 1)
        Next i

        Console.Write("evenNumbers contains {0} elements: ", evenNumbers.Count)
        DisplaySet(evenNumbers)

        Console.Write("oddNumbers contains {0} elements: ", oddNumbers.Count)
        DisplaySet(oddNumbers)

        ' Create a new HashSet populated with even numbers.
        Dim numbers As HashSet(Of Integer) = New HashSet(Of Integer)(evenNumbers)
        Console.WriteLine("numbers UnionWith oddNumbers...")
        numbers.UnionWith(oddNumbers)

        Console.Write("numbers contains {0} elements: ", numbers.Count)
        DisplaySet(numbers)
    End Sub


    Private Shared Sub DisplaySet(ByVal collection As HashSet(Of Integer))
        Console.Write("{")
        For Each i As Integer In collection
            Console.Write(" {0}", i)
        Next i
        Console.WriteLine(" }")
    End Sub

End Class
' This example produces output similar to the following:
' evenNumbers contains 5 elements: { 0 2 4 6 8 }
' oddNumbers contains 5 elements: { 1 3 5 7 9 }
' numbers UnionWith oddNumbers...
' numbers contains 10 elements: { 0 2 4 6 8 1 3 5 7 9 }

Remarks

For more information about this API, see Supplemental API remarks for HashSet<T>.

Constructors

HashSet<T>()	Initializes a new instance of the HashSet<T> class that is empty and uses the default equality comparer for the set type.
HashSet<T>(IEnumerable<T>, IEqualityComparer<T>)	Initializes a new instance of the HashSet<T> class that uses the specified equality comparer for the set type, contains elements copied from the specified collection, and has sufficient capacity to accommodate the number of elements copied.
HashSet<T>(IEnumerable<T>)	Initializes a new instance of the HashSet<T> class that uses the default equality comparer for the set type, contains elements copied from the specified collection, and has sufficient capacity to accommodate the number of elements copied.
HashSet<T>(IEqualityComparer<T>)	Initializes a new instance of the HashSet<T> class that is empty and uses the specified equality comparer for the set type.
HashSet<T>(Int32, IEqualityComparer<T>)	Initializes a new instance of the HashSet<T> class that uses the specified equality comparer for the set type, and has sufficient capacity to accommodate capacity elements.
HashSet<T>(Int32)	Initializes a new instance of the HashSet<T> class that is empty, but has reserved space for capacity items and uses the default equality comparer for the set type.
HashSet<T>(SerializationInfo, StreamingContext)	Obsolete. Initializes a new instance of the HashSet<T> class with serialized data.

Properties

Capacity	Gets the total numbers of elements the internal data structure can hold without resizing.
Comparer	Gets the IEqualityComparer<T> object that is used to determine equality for the values in the set.
Count	Gets the number of elements that are contained in a set.

Methods

Add(T)	Adds the specified element to a set.
Clear()	Removes all elements from a HashSet<T> object.
Contains(T)	Determines whether a HashSet<T> object contains the specified element.
CopyTo(T[], Int32, Int32)	Copies the specified number of elements of a HashSet<T> object to an array, starting at the specified array index.
CopyTo(T[], Int32)	Copies the elements of a HashSet<T> object to an array, starting at the specified array index.
CopyTo(T[])	Copies the elements of a HashSet<T> object to an array.
CreateSetComparer()	Returns an IEqualityComparer object that can be used for equality testing of a HashSet<T> object.
EnsureCapacity(Int32)	Ensures that this hash set can hold the specified number of elements without any further expansion of its backing storage.
Equals(Object)	Determines whether the specified object is equal to the current object. (Inherited from Object)
ExceptWith(IEnumerable<T>)	Removes all elements in the specified collection from the current HashSet<T> object.
GetAlternateLookup<TAlternate>()	Gets an instance of a type that can be used to perform operations on the current HashSet<T> using a TAlternate instead of a T.
GetEnumerator()	Returns an enumerator that iterates through a HashSet<T> object.
GetHashCode()	Serves as the default hash function. (Inherited from Object)
GetObjectData(SerializationInfo, StreamingContext)	Obsolete. Implements the ISerializable interface and returns the data needed to serialize a HashSet<T> object.
GetType()	Gets the Type of the current instance. (Inherited from Object)
IntersectWith(IEnumerable<T>)	Modifies the current HashSet<T> object to contain only elements that are present in that object and in the specified collection.
IsProperSubsetOf(IEnumerable<T>)	Determines whether a HashSet<T> object is a proper subset of the specified collection.
IsProperSupersetOf(IEnumerable<T>)	Determines whether a HashSet<T> object is a proper superset of the specified collection.
IsSubsetOf(IEnumerable<T>)	Determines whether a HashSet<T> object is a subset of the specified collection.
IsSupersetOf(IEnumerable<T>)	Determines whether a HashSet<T> object is a superset of the specified collection.
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
OnDeserialization(Object)	Implements the ISerializable interface and raises the deserialization event when the deserialization is complete.
Overlaps(IEnumerable<T>)	Determines whether the current HashSet<T> object and a specified collection share common elements.
Remove(T)	Removes the specified element from a HashSet<T> object.
RemoveWhere(Predicate<T>)	Removes all elements that match the conditions defined by the specified predicate from a HashSet<T> collection.
SetEquals(IEnumerable<T>)	Determines whether a HashSet<T> object and the specified collection contain the same elements.
SymmetricExceptWith(IEnumerable<T>)	Modifies the current HashSet<T> object to contain only elements that are present either in that object or in the specified collection, but not both.
ToString()	Returns a string that represents the current object. (Inherited from Object)
TrimExcess()	Sets the capacity of a HashSet<T> object to the actual number of elements it contains, rounded up to a nearby, implementation-specific value.
TrimExcess(Int32)	Sets the capacity of a HashSet<T> object to the specified number of entries, rounded up to a nearby, implementation-specific value.
TryGetAlternateLookup<TAlternate>(HashSet<T>.AlternateLookup<TAlternate>)	Gets an instance of a type that can be used to perform operations on the current HashSet<T> using a TAlternate instead of a T.
TryGetValue(T, T)	Searches the set for a given value and returns the equal value it finds, if any.
UnionWith(IEnumerable<T>)	Modifies the current HashSet<T> object to contain all elements that are present in itself, the specified collection, or both.

Explicit Interface Implementations

ICollection<T>.Add(T)	Adds an item to an ICollection<T> object.
ICollection<T>.IsReadOnly	Gets a value indicating whether a collection is read-only.
IEnumerable.GetEnumerator()	Returns an enumerator that iterates through a collection.
IEnumerable<T>.GetEnumerator()	Returns an enumerator that iterates through a collection.

Extension Methods

ToFrozenDictionary<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>)	Creates a FrozenDictionary<TKey,TValue> from an IEnumerable<T> according to specified key selector function.
ToFrozenDictionary<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>)	Creates a FrozenDictionary<TKey,TValue> from an IEnumerable<T> according to specified key selector and element selector functions.
ToFrozenSet<T>(IEnumerable<T>, IEqualityComparer<T>)	Creates a FrozenSet<T> with the specified values.
ToImmutableArray<TSource>(IEnumerable<TSource>)	Creates an immutable array from the specified collection.
ToImmutableDictionary<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>)	Constructs an immutable dictionary based on some transformation of a sequence.
ToImmutableDictionary<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)	Constructs an immutable dictionary from an existing collection of elements, applying a transformation function to the source keys.
ToImmutableDictionary<TSource,TKey,TValue>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TValue>, IEqualityComparer<TKey>, IEqualityComparer<TValue>)	Enumerates and transforms a sequence, and produces an immutable dictionary of its contents by using the specified key and value comparers.
ToImmutableDictionary<TSource,TKey,TValue>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TValue>, IEqualityComparer<TKey>)	Enumerates and transforms a sequence, and produces an immutable dictionary of its contents by using the specified key comparer.
ToImmutableDictionary<TSource,TKey,TValue>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TValue>)	Enumerates and transforms a sequence, and produces an immutable dictionary of its contents.
ToImmutableHashSet<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>)	Enumerates a sequence, produces an immutable hash set of its contents, and uses the specified equality comparer for the set type.
ToImmutableHashSet<TSource>(IEnumerable<TSource>)	Enumerates a sequence and produces an immutable hash set of its contents.
ToImmutableList<TSource>(IEnumerable<TSource>)	Enumerates a sequence and produces an immutable list of its contents.
ToImmutableSortedDictionary<TSource,TKey,TValue>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TValue>, IComparer<TKey>, IEqualityComparer<TValue>)	Enumerates and transforms a sequence, and produces an immutable sorted dictionary of its contents by using the specified key and value comparers.
ToImmutableSortedDictionary<TSource,TKey,TValue>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TValue>, IComparer<TKey>)	Enumerates and transforms a sequence, and produces an immutable sorted dictionary of its contents by using the specified key comparer.
ToImmutableSortedDictionary<TSource,TKey,TValue>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TValue>)	Enumerates and transforms a sequence, and produces an immutable sorted dictionary of its contents.
ToImmutableSortedSet<TSource>(IEnumerable<TSource>, IComparer<TSource>)	Enumerates a sequence, produces an immutable sorted set of its contents, and uses the specified comparer.
ToImmutableSortedSet<TSource>(IEnumerable<TSource>)	Enumerates a sequence and produces an immutable sorted set of its contents.
CopyToDataTable<T>(IEnumerable<T>, DataTable, LoadOption, FillErrorEventHandler)	Copies DataRow objects to the specified DataTable, given an input IEnumerable<T> object where the generic parameter T is DataRow.
CopyToDataTable<T>(IEnumerable<T>, DataTable, LoadOption)	Copies DataRow objects to the specified DataTable, given an input IEnumerable<T> object where the generic parameter T is DataRow.
CopyToDataTable<T>(IEnumerable<T>)	Returns a DataTable that contains copies of the DataRow objects, given an input IEnumerable<T> object where the generic parameter T is DataRow.
Aggregate<TSource>(IEnumerable<TSource>, Func<TSource,TSource,TSource>)	Applies an accumulator function over a sequence.
Aggregate<TSource,TAccumulate>(IEnumerable<TSource>, TAccumulate, Func<TAccumulate,TSource,TAccumulate>)	Applies an accumulator function over a sequence. The specified seed value is used as the initial accumulator value.
Aggregate<TSource,TAccumulate,TResult>(IEnumerable<TSource>, TAccumulate, Func<TAccumulate,TSource,TAccumulate>, Func<TAccumulate,TResult>)	Applies an accumulator function over a sequence. The specified seed value is used as the initial accumulator value, and the specified function is used to select the result value.
AggregateBy<TSource,TKey,TAccumulate>(IEnumerable<TSource>, Func<TSource, TKey>, TAccumulate, Func<TAccumulate,TSource,TAccumulate>, IEqualityComparer<TKey>)	Applies an accumulator function over a sequence, grouping results by key.
AggregateBy<TSource,TKey,TAccumulate>(IEnumerable<TSource>, Func<TSource, TKey>, Func<TKey,TAccumulate>, Func<TAccumulate,TSource,TAccumulate>, IEqualityComparer<TKey>)	Applies an accumulator function over a sequence, grouping results by key.
All<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Determines whether all elements of a sequence satisfy a condition.
Any<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Determines whether any element of a sequence satisfies a condition.
Any<TSource>(IEnumerable<TSource>)	Determines whether a sequence contains any elements.
Append<TSource>(IEnumerable<TSource>, TSource)	Appends a value to the end of the sequence.
AsEnumerable<TSource>(IEnumerable<TSource>)	Returns the input typed as IEnumerable<T>.
Average<TSource>(IEnumerable<TSource>, Func<TSource,Decimal>)	Computes the average of a sequence of Decimal values that are obtained by invoking a transform function on each element of the input sequence.
Average<TSource>(IEnumerable<TSource>, Func<TSource,Double>)	Computes the average of a sequence of Double values that are obtained by invoking a transform function on each element of the input sequence.
Average<TSource>(IEnumerable<TSource>, Func<TSource,Int32>)	Computes the average of a sequence of Int32 values that are obtained by invoking a transform function on each element of the input sequence.
Average<TSource>(IEnumerable<TSource>, Func<TSource,Int64>)	Computes the average of a sequence of Int64 values that are obtained by invoking a transform function on each element of the input sequence.
Average<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Decimal>>)	Computes the average of a sequence of nullable Decimal values that are obtained by invoking a transform function on each element of the input sequence.
Average<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Double>>)	Computes the average of a sequence of nullable Double values that are obtained by invoking a transform function on each element of the input sequence.
Average<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int32>>)	Computes the average of a sequence of nullable Int32 values that are obtained by invoking a transform function on each element of the input sequence.
Average<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int64>>)	Computes the average of a sequence of nullable Int64 values that are obtained by invoking a transform function on each element of the input sequence.
Average<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Single>>)	Computes the average of a sequence of nullable Single values that are obtained by invoking a transform function on each element of the input sequence.
Average<TSource>(IEnumerable<TSource>, Func<TSource,Single>)	Computes the average of a sequence of Single values that are obtained by invoking a transform function on each element of the input sequence.
Cast<TResult>(IEnumerable)	Casts the elements of an IEnumerable to the specified type.
Chunk<TSource>(IEnumerable<TSource>, Int32)	Splits the elements of a sequence into chunks of size at most size.
Concat<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)	Concatenates two sequences.
Contains<TSource>(IEnumerable<TSource>, TSource, IEqualityComparer<TSource>)	Determines whether a sequence contains a specified element by using a specified IEqualityComparer<T>.
Contains<TSource>(IEnumerable<TSource>, TSource)	Determines whether a sequence contains a specified element by using the default equality comparer.
Count<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Returns a number that represents how many elements in the specified sequence satisfy a condition.
Count<TSource>(IEnumerable<TSource>)	Returns the number of elements in a sequence.
CountBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>)	Returns the count of elements in the source sequence grouped by key.
DefaultIfEmpty<TSource>(IEnumerable<TSource>, TSource)	Returns the elements of the specified sequence or the specified value in a singleton collection if the sequence is empty.
DefaultIfEmpty<TSource>(IEnumerable<TSource>)	Returns the elements of the specified sequence or the type parameter's default value in a singleton collection if the sequence is empty.
Distinct<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>)	Returns distinct elements from a sequence by using a specified IEqualityComparer<T> to compare values.
Distinct<TSource>(IEnumerable<TSource>)	Returns distinct elements from a sequence by using the default equality comparer to compare values.
DistinctBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>)	Returns distinct elements from a sequence according to a specified key selector function and using a specified comparer to compare keys.
DistinctBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)	Returns distinct elements from a sequence according to a specified key selector function.
ElementAt<TSource>(IEnumerable<TSource>, Index)	Returns the element at a specified index in a sequence.
ElementAt<TSource>(IEnumerable<TSource>, Int32)	Returns the element at a specified index in a sequence.
ElementAtOrDefault<TSource>(IEnumerable<TSource>, Index)	Returns the element at a specified index in a sequence or a default value if the index is out of range.
ElementAtOrDefault<TSource>(IEnumerable<TSource>, Int32)	Returns the element at a specified index in a sequence or a default value if the index is out of range.
Except<TSource>(IEnumerable<TSource>, IEnumerable<TSource>, IEqualityComparer<TSource>)	Produces the set difference of two sequences by using the specified IEqualityComparer<T> to compare values.
Except<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)	Produces the set difference of two sequences by using the default equality comparer to compare values.
ExceptBy<TSource,TKey>(IEnumerable<TSource>, IEnumerable<TKey>, Func<TSource,TKey>, IEqualityComparer<TKey>)	Produces the set difference of two sequences according to a specified key selector function.
ExceptBy<TSource,TKey>(IEnumerable<TSource>, IEnumerable<TKey>, Func<TSource,TKey>)	Produces the set difference of two sequences according to a specified key selector function.
First<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Returns the first element in a sequence that satisfies a specified condition.
First<TSource>(IEnumerable<TSource>)	Returns the first element of a sequence.
FirstOrDefault<TSource>(IEnumerable<TSource>, TSource)	Returns the first element of a sequence, or a specified default value if the sequence contains no elements.
FirstOrDefault<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>, TSource)	Returns the first element of the sequence that satisfies a condition, or a specified default value if no such element is found.
FirstOrDefault<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Returns the first element of the sequence that satisfies a condition or a default value if no such element is found.
FirstOrDefault<TSource>(IEnumerable<TSource>)	Returns the first element of a sequence, or a default value if the sequence contains no elements.
GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>)	Groups the elements of a sequence according to a specified key selector function and compares the keys by using a specified comparer.
GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)	Groups the elements of a sequence according to a specified key selector function.
GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>)	Groups the elements of a sequence according to a key selector function. The keys are compared by using a comparer and each group's elements are projected by using a specified function.
GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>)	Groups the elements of a sequence according to a specified key selector function and projects the elements for each group by using a specified function.
GroupBy<TSource,TKey,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TKey,IEnumerable<TSource>,TResult>, IEqualityComparer<TKey>)	Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. The keys are compared by using a specified comparer.
GroupBy<TSource,TKey,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TKey,IEnumerable<TSource>,TResult>)	Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key.
GroupBy<TSource,TKey,TElement,TResult>(IEnumerable<TSource>, Func<TSource, TKey>, Func<TSource,TElement>, Func<TKey,IEnumerable<TElement>, TResult>, IEqualityComparer<TKey>)	Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. Key values are compared by using a specified comparer, and the elements of each group are projected by using a specified function.
GroupBy<TSource,TKey,TElement,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, Func<TKey,IEnumerable<TElement>,TResult>)	Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. The elements of each group are projected by using a specified function.
GroupJoin<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,IEnumerable<TInner>, TResult>, IEqualityComparer<TKey>)	Correlates the elements of two sequences based on key equality and groups the results. A specified IEqualityComparer<T> is used to compare keys.
GroupJoin<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,IEnumerable<TInner>, TResult>)	Correlates the elements of two sequences based on equality of keys and groups the results. The default equality comparer is used to compare keys.
Index<TSource>(IEnumerable<TSource>)	Returns an enumerable that incorporates the element's index into a tuple.
Intersect<TSource>(IEnumerable<TSource>, IEnumerable<TSource>, IEqualityComparer<TSource>)	Produces the set intersection of two sequences by using the specified IEqualityComparer<T> to compare values.
Intersect<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)	Produces the set intersection of two sequences by using the default equality comparer to compare values.
IntersectBy<TSource,TKey>(IEnumerable<TSource>, IEnumerable<TKey>, Func<TSource,TKey>, IEqualityComparer<TKey>)	Produces the set intersection of two sequences according to a specified key selector function.
IntersectBy<TSource,TKey>(IEnumerable<TSource>, IEnumerable<TKey>, Func<TSource,TKey>)	Produces the set intersection of two sequences according to a specified key selector function.
Join<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,TInner,TResult>, IEqualityComparer<TKey>)	Correlates the elements of two sequences based on matching keys. A specified IEqualityComparer<T> is used to compare keys.
Join<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,TInner,TResult>)	Correlates the elements of two sequences based on matching keys. The default equality comparer is used to compare keys.
Last<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Returns the last element of a sequence that satisfies a specified condition.
Last<TSource>(IEnumerable<TSource>)	Returns the last element of a sequence.
LastOrDefault<TSource>(IEnumerable<TSource>, TSource)	Returns the last element of a sequence, or a specified default value if the sequence contains no elements.
LastOrDefault<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>, TSource)	Returns the last element of a sequence that satisfies a condition, or a specified default value if no such element is found.
LastOrDefault<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Returns the last element of a sequence that satisfies a condition or a default value if no such element is found.
LastOrDefault<TSource>(IEnumerable<TSource>)	Returns the last element of a sequence, or a default value if the sequence contains no elements.
LongCount<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Returns an Int64 that represents how many elements in a sequence satisfy a condition.
LongCount<TSource>(IEnumerable<TSource>)	Returns an Int64 that represents the total number of elements in a sequence.
Max<TSource>(IEnumerable<TSource>, IComparer<TSource>)	Returns the maximum value in a generic sequence.
Max<TSource>(IEnumerable<TSource>, Func<TSource,Decimal>)	Invokes a transform function on each element of a sequence and returns the maximum Decimal value.
Max<TSource>(IEnumerable<TSource>, Func<TSource,Double>)	Invokes a transform function on each element of a sequence and returns the maximum Double value.
Max<TSource>(IEnumerable<TSource>, Func<TSource,Int32>)	Invokes a transform function on each element of a sequence and returns the maximum Int32 value.
Max<TSource>(IEnumerable<TSource>, Func<TSource,Int64>)	Invokes a transform function on each element of a sequence and returns the maximum Int64 value.
Max<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Decimal>>)	Invokes a transform function on each element of a sequence and returns the maximum nullable Decimal value.
Max<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Double>>)	Invokes a transform function on each element of a sequence and returns the maximum nullable Double value.
Max<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int32>>)	Invokes a transform function on each element of a sequence and returns the maximum nullable Int32 value.
Max<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int64>>)	Invokes a transform function on each element of a sequence and returns the maximum nullable Int64 value.
Max<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Single>>)	Invokes a transform function on each element of a sequence and returns the maximum nullable Single value.
Max<TSource>(IEnumerable<TSource>, Func<TSource,Single>)	Invokes a transform function on each element of a sequence and returns the maximum Single value.
Max<TSource>(IEnumerable<TSource>)	Returns the maximum value in a generic sequence.
Max<TSource,TResult>(IEnumerable<TSource>, Func<TSource,TResult>)	Invokes a transform function on each element of a generic sequence and returns the maximum resulting value.
MaxBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IComparer<TKey>)	Returns the maximum value in a generic sequence according to a specified key selector function and key comparer.
MaxBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)	Returns the maximum value in a generic sequence according to a specified key selector function.
Min<TSource>(IEnumerable<TSource>, IComparer<TSource>)	Returns the minimum value in a generic sequence.
Min<TSource>(IEnumerable<TSource>, Func<TSource,Decimal>)	Invokes a transform function on each element of a sequence and returns the minimum Decimal value.
Min<TSource>(IEnumerable<TSource>, Func<TSource,Double>)	Invokes a transform function on each element of a sequence and returns the minimum Double value.
Min<TSource>(IEnumerable<TSource>, Func<TSource,Int32>)	Invokes a transform function on each element of a sequence and returns the minimum Int32 value.
Min<TSource>(IEnumerable<TSource>, Func<TSource,Int64>)	Invokes a transform function on each element of a sequence and returns the minimum Int64 value.
Min<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Decimal>>)	Invokes a transform function on each element of a sequence and returns the minimum nullable Decimal value.
Min<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Double>>)	Invokes a transform function on each element of a sequence and returns the minimum nullable Double value.
Min<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int32>>)	Invokes a transform function on each element of a sequence and returns the minimum nullable Int32 value.
Min<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int64>>)	Invokes a transform function on each element of a sequence and returns the minimum nullable Int64 value.
Min<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Single>>)	Invokes a transform function on each element of a sequence and returns the minimum nullable Single value.
Min<TSource>(IEnumerable<TSource>, Func<TSource,Single>)	Invokes a transform function on each element of a sequence and returns the minimum Single value.
Min<TSource>(IEnumerable<TSource>)	Returns the minimum value in a generic sequence.
Min<TSource,TResult>(IEnumerable<TSource>, Func<TSource,TResult>)	Invokes a transform function on each element of a generic sequence and returns the minimum resulting value.
MinBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IComparer<TKey>)	Returns the minimum value in a generic sequence according to a specified key selector function and key comparer.
MinBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)	Returns the minimum value in a generic sequence according to a specified key selector function.
OfType<TResult>(IEnumerable)	Filters the elements of an IEnumerable based on a specified type.
Order<T>(IEnumerable<T>, IComparer<T>)	Sorts the elements of a sequence in ascending order.
Order<T>(IEnumerable<T>)	Sorts the elements of a sequence in ascending order.
OrderBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IComparer<TKey>)	Sorts the elements of a sequence in ascending order by using a specified comparer.
OrderBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)	Sorts the elements of a sequence in ascending order according to a key.
OrderByDescending<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IComparer<TKey>)	Sorts the elements of a sequence in descending order by using a specified comparer.
OrderByDescending<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)	Sorts the elements of a sequence in descending order according to a key.
OrderDescending<T>(IEnumerable<T>, IComparer<T>)	Sorts the elements of a sequence in descending order.
OrderDescending<T>(IEnumerable<T>)	Sorts the elements of a sequence in descending order.
Prepend<TSource>(IEnumerable<TSource>, TSource)	Adds a value to the beginning of the sequence.
Reverse<TSource>(IEnumerable<TSource>)	Inverts the order of the elements in a sequence.
Select<TSource,TResult>(IEnumerable<TSource>, Func<TSource,TResult>)	Projects each element of a sequence into a new form.
Select<TSource,TResult>(IEnumerable<TSource>, Func<TSource,Int32,TResult>)	Projects each element of a sequence into a new form by incorporating the element's index.
SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TResult>>)	Projects each element of a sequence to an IEnumerable<T> and flattens the resulting sequences into one sequence.
SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TResult>>)	Projects each element of a sequence to an IEnumerable<T>, and flattens the resulting sequences into one sequence. The index of each source element is used in the projected form of that element.
SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>)	Projects each element of a sequence to an IEnumerable<T>, flattens the resulting sequences into one sequence, and invokes a result selector function on each element therein.
SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>)	Projects each element of a sequence to an IEnumerable<T>, flattens the resulting sequences into one sequence, and invokes a result selector function on each element therein. The index of each source element is used in the intermediate projected form of that element.
SequenceEqual<TSource>(IEnumerable<TSource>, IEnumerable<TSource>, IEqualityComparer<TSource>)	Determines whether two sequences are equal by comparing their elements by using a specified IEqualityComparer<T>.
SequenceEqual<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)	Determines whether two sequences are equal by comparing the elements by using the default equality comparer for their type.
Single<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Returns the only element of a sequence that satisfies a specified condition, and throws an exception if more than one such element exists.
Single<TSource>(IEnumerable<TSource>)	Returns the only element of a sequence, and throws an exception if there is not exactly one element in the sequence.
SingleOrDefault<TSource>(IEnumerable<TSource>, TSource)	Returns the only element of a sequence, or a specified default value if the sequence is empty; this method throws an exception if there is more than one element in the sequence.
SingleOrDefault<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>, TSource)	Returns the only element of a sequence that satisfies a specified condition, or a specified default value if no such element exists; this method throws an exception if more than one element satisfies the condition.
SingleOrDefault<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Returns the only element of a sequence that satisfies a specified condition or a default value if no such element exists; this method throws an exception if more than one element satisfies the condition.
SingleOrDefault<TSource>(IEnumerable<TSource>)	Returns the only element of a sequence, or a default value if the sequence is empty; this method throws an exception if there is more than one element in the sequence.
Skip<TSource>(IEnumerable<TSource>, Int32)	Bypasses a specified number of elements in a sequence and then returns the remaining elements.
SkipLast<TSource>(IEnumerable<TSource>, Int32)	Returns a new enumerable collection that contains the elements from source with the last count elements of the source collection omitted.
SkipWhile<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Bypasses elements in a sequence as long as a specified condition is true and then returns the remaining elements.
SkipWhile<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>)	Bypasses elements in a sequence as long as a specified condition is true and then returns the remaining elements. The element's index is used in the logic of the predicate function.
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Decimal>)	Computes the sum of the sequence of Decimal values that are obtained by invoking a transform function on each element of the input sequence.
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Double>)	Computes the sum of the sequence of Double values that are obtained by invoking a transform function on each element of the input sequence.
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Int32>)	Computes the sum of the sequence of Int32 values that are obtained by invoking a transform function on each element of the input sequence.
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Int64>)	Computes the sum of the sequence of Int64 values that are obtained by invoking a transform function on each element of the input sequence.
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Decimal>>)	Computes the sum of the sequence of nullable Decimal values that are obtained by invoking a transform function on each element of the input sequence.
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Double>>)	Computes the sum of the sequence of nullable Double values that are obtained by invoking a transform function on each element of the input sequence.
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int32>>)	Computes the sum of the sequence of nullable Int32 values that are obtained by invoking a transform function on each element of the input sequence.
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int64>>)	Computes the sum of the sequence of nullable Int64 values that are obtained by invoking a transform function on each element of the input sequence.
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Single>>)	Computes the sum of the sequence of nullable Single values that are obtained by invoking a transform function on each element of the input sequence.
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Single>)	Computes the sum of the sequence of Single values that are obtained by invoking a transform function on each element of the input sequence.
Take<TSource>(IEnumerable<TSource>, Int32)	Returns a specified number of contiguous elements from the start of a sequence.
Take<TSource>(IEnumerable<TSource>, Range)	Returns a specified range of contiguous elements from a sequence.
TakeLast<TSource>(IEnumerable<TSource>, Int32)	Returns a new enumerable collection that contains the last count elements from source.
TakeWhile<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Returns elements from a sequence as long as a specified condition is true.
TakeWhile<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>)	Returns elements from a sequence as long as a specified condition is true. The element's index is used in the logic of the predicate function.
ToArray<TSource>(IEnumerable<TSource>)	Creates an array from a IEnumerable<T>.
ToDictionary<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>)	Creates a Dictionary<TKey,TValue> from an IEnumerable<T> according to a specified key selector function and key comparer.
ToDictionary<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)	Creates a Dictionary<TKey,TValue> from an IEnumerable<T> according to a specified key selector function.
ToDictionary<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>)	Creates a Dictionary<TKey,TValue> from an IEnumerable<T> according to a specified key selector function, a comparer, and an element selector function.
ToDictionary<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>)	Creates a Dictionary<TKey,TValue> from an IEnumerable<T> according to specified key selector and element selector functions.
ToHashSet<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>)	Creates a HashSet<T> from an IEnumerable<T> using the comparer to compare keys.
ToHashSet<TSource>(IEnumerable<TSource>)	Creates a HashSet<T> from an IEnumerable<T>.
ToList<TSource>(IEnumerable<TSource>)	Creates a List<T> from an IEnumerable<T>.
ToLookup<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>)	Creates a Lookup<TKey,TElement> from an IEnumerable<T> according to a specified key selector function and key comparer.
ToLookup<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)	Creates a Lookup<TKey,TElement> from an IEnumerable<T> according to a specified key selector function.
ToLookup<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>)	Creates a Lookup<TKey,TElement> from an IEnumerable<T> according to a specified key selector function, a comparer and an element selector function.
ToLookup<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>)	Creates a Lookup<TKey,TElement> from an IEnumerable<T> according to specified key selector and element selector functions.
TryGetNonEnumeratedCount<TSource>(IEnumerable<TSource>, Int32)	Attempts to determine the number of elements in a sequence without forcing an enumeration.
Union<TSource>(IEnumerable<TSource>, IEnumerable<TSource>, IEqualityComparer<TSource>)	Produces the set union of two sequences by using a specified IEqualityComparer<T>.
Union<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)	Produces the set union of two sequences by using the default equality comparer.
UnionBy<TSource,TKey>(IEnumerable<TSource>, IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>)	Produces the set union of two sequences according to a specified key selector function.
UnionBy<TSource,TKey>(IEnumerable<TSource>, IEnumerable<TSource>, Func<TSource,TKey>)	Produces the set union of two sequences according to a specified key selector function.
Where<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Filters a sequence of values based on a predicate.
Where<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>)	Filters a sequence of values based on a predicate. Each element's index is used in the logic of the predicate function.
Zip<TFirst,TSecond>(IEnumerable<TFirst>, IEnumerable<TSecond>)	Produces a sequence of tuples with elements from the two specified sequences.
Zip<TFirst,TSecond,TThird>(IEnumerable<TFirst>, IEnumerable<TSecond>, IEnumerable<TThird>)	Produces a sequence of tuples with elements from the three specified sequences.
Zip<TFirst,TSecond,TResult>(IEnumerable<TFirst>, IEnumerable<TSecond>, Func<TFirst,TSecond,TResult>)	Applies a specified function to the corresponding elements of two sequences, producing a sequence of the results.
AsParallel(IEnumerable)	Enables parallelization of a query.
AsParallel<TSource>(IEnumerable<TSource>)	Enables parallelization of a query.
AsQueryable(IEnumerable)	Converts an IEnumerable to an IQueryable.
AsQueryable<TElement>(IEnumerable<TElement>)	Converts a generic IEnumerable<T> to a generic IQueryable<T>.
Ancestors<T>(IEnumerable<T>, XName)	Returns a filtered collection of elements that contains the ancestors of every node in the source collection. Only elements that have a matching XName are included in the collection.
Ancestors<T>(IEnumerable<T>)	Returns a collection of elements that contains the ancestors of every node in the source collection.
DescendantNodes<T>(IEnumerable<T>)	Returns a collection of the descendant nodes of every document and element in the source collection.
Descendants<T>(IEnumerable<T>, XName)	Returns a filtered collection of elements that contains the descendant elements of every element and document in the source collection. Only elements that have a matching XName are included in the collection.
Descendants<T>(IEnumerable<T>)	Returns a collection of elements that contains the descendant elements of every element and document in the source collection.
Elements<T>(IEnumerable<T>, XName)	Returns a filtered collection of the child elements of every element and document in the source collection. Only elements that have a matching XName are included in the collection.
Elements<T>(IEnumerable<T>)	Returns a collection of the child elements of every element and document in the source collection.
InDocumentOrder<T>(IEnumerable<T>)	Returns a collection of nodes that contains all nodes in the source collection, sorted in document order.
Nodes<T>(IEnumerable<T>)	Returns a collection of the child nodes of every document and element in the source collection.
Remove<T>(IEnumerable<T>)	Removes every node in the source collection from its parent node.

See also

• SortedSet<T>
• ISet<T>