Статья
11/18/2011

List<T> Class

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Represents a strongly typed list of objects that can be accessed by index. Provides methods to search, sort, and manipulate lists.

Inheritance Hierarchy

System.Object
System.Collections.Generic.List<T>

Namespace: System.Collections.Generic
Assembly: mscorlib (in mscorlib.dll)

Syntax

'Declaration
<DebuggerDisplayAttribute("Count = {Count}")> _
<DefaultMemberAttribute("Item")> _
Public Class List(Of T) _
    Implements IList(Of T), ICollection(Of T),  _
    IList, ICollection, IEnumerable(Of T), IEnumerable

[DebuggerDisplayAttribute("Count = {Count}")]
[DefaultMemberAttribute("Item")]
public class List<T> : IList<T>, ICollection<T>, 
    IList, ICollection, IEnumerable<T>, IEnumerable

Type Parameters

T
The type of elements in the list.

The List<T> type exposes the following members.

Constructors

	Name	Description
	List<T>()	Initializes a new instance of the List<T> class that is empty and has the default initial capacity.
	List<T>(IEnumerable<T>)	Initializes a new instance of the List<T> class that contains elements copied from the specified collection and has sufficient capacity to accommodate the number of elements copied.
	List<T>(Int32)	Initializes a new instance of the List<T> class that is empty and has the specified initial capacity.

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Properties

	Name	Description
	Capacity	Gets or sets the total number of elements the internal data structure can hold without resizing.
	Count	Gets the number of elements actually contained in the List<T>.
	Item	Gets or sets the element at the specified index.

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Methods

	Name	Description
	Add	Adds an object to the end of the List<T>.
	AddRange	Adds the elements of the specified collection to the end of the List<T>.
	AsReadOnly	Returns a read-only IList<T> wrapper for the current collection.
	BinarySearch(T)	Searches the entire sorted List<T> for an element using the default comparer and returns the zero-based index of the element.
	BinarySearch(T, IComparer<T>)	Searches the entire sorted List<T> for an element using the specified comparer and returns the zero-based index of the element.
	BinarySearch(Int32, Int32, T, IComparer<T>)	Searches a range of elements in the sorted List<T> for an element using the specified comparer and returns the zero-based index of the element.
	Clear	Removes all elements from the List<T>.
	Contains	Determines whether an element is in the List<T>.
	CopyTo(array<T[])	Copies the entire List<T> to a compatible one-dimensional array, starting at the beginning of the target array.
	CopyTo(array<T[], Int32)	Copies the entire List<T> to a compatible one-dimensional array, starting at the specified index of the target array.
	CopyTo(Int32, array<T[], Int32, Int32)	Copies a range of elements from the List<T> to a compatible one-dimensional array, starting at the specified index of the target array.
	Equals(Object)	Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
	Finalize	Allows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
	ForEach	Performs the specified action on each element of the List<T>.
	GetEnumerator	Returns an enumerator that iterates through the List<T>.
	GetHashCode	Serves as a hash function for a particular type. (Inherited from Object.)
	GetRange	Creates a shallow copy of a range of elements in the source List<T>.
	GetType	Gets the Type of the current instance. (Inherited from Object.)
	IndexOf(T)	Searches for the specified object and returns the zero-based index of the first occurrence within the entire List<T>.
	IndexOf(T, Int32)	Searches for the specified object and returns the zero-based index of the first occurrence within the range of elements in the List<T> that extends from the specified index to the last element.
	IndexOf(T, Int32, Int32)	Searches for the specified object and returns the zero-based index of the first occurrence within the range of elements in the List<T> that starts at the specified index and contains the specified number of elements.
	Insert	Inserts an element into the List<T> at the specified index.
	InsertRange	Inserts the elements of a collection into the List<T> at the specified index.
	LastIndexOf(T)	Searches for the specified object and returns the zero-based index of the last occurrence within the entire List<T>.
	LastIndexOf(T, Int32)	Searches for the specified object and returns the zero-based index of the last occurrence within the range of elements in the List<T> that extends from the first element to the specified index.
	LastIndexOf(T, Int32, Int32)	Searches for the specified object and returns the zero-based index of the last occurrence within the range of elements in the List<T> that contains the specified number of elements and ends at the specified index.
	MemberwiseClone	Creates a shallow copy of the current Object. (Inherited from Object.)
	Remove	Removes the first occurrence of a specific object from the List<T>.
	RemoveAll	Removes all the elements that match the conditions defined by the specified predicate.
	RemoveAt	Removes the element at the specified index of the List<T>.
	RemoveRange	Removes a range of elements from the List<T>.
	Reverse()	Reverses the order of the elements in the entire List<T>.
	Reverse(Int32, Int32)	Reverses the order of the elements in the specified range.
	Sort()	Sorts the elements in the entire List<T> using the default comparer.
	Sort(Comparison<T>)	Sorts the elements in the entire List<T> using the specified System.Comparison<T>.
	Sort(IComparer<T>)	Sorts the elements in the entire List<T> using the specified comparer.
	Sort(Int32, Int32, IComparer<T>)	Sorts the elements in a range of elements in List<T> using the specified comparer.
	ToArray	Copies the elements of the List<T> to a new array.
	ToString	Returns a string that represents the current object. (Inherited from Object.)
	TrimExcess	Sets the capacity to the actual number of elements in the List<T>, if that number is less than a threshold value.

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Extension Methods

	Name	Description
	Aggregate<T>(Func<T, T, T>)	Overloaded. Applies an accumulator function over a sequence. (Defined by Enumerable.)
	Aggregate<T, TAccumulate>(TAccumulate, Func<TAccumulate, T, TAccumulate>)	Overloaded. Applies an accumulator function over a sequence. The specified seed value is used as the initial accumulator value. (Defined by Enumerable.)
	Aggregate<T, TAccumulate, TResult>(TAccumulate, Func<TAccumulate, T, TAccumulate>, Func<TAccumulate, TResult>)	Overloaded. 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. (Defined by Enumerable.)
	All<T>	Determines whether all elements of a sequence satisfy a condition. (Defined by Enumerable.)
	Any<T>()	Overloaded. Determines whether a sequence contains any elements. (Defined by Enumerable.)
	Any<T>(Func<T, Boolean>)	Overloaded. Determines whether any element of a sequence satisfies a condition. (Defined by Enumerable.)
	AsEnumerable<T>	Returns the input typed as IEnumerable<T>. (Defined by Enumerable.)
	AsQueryable()	Overloaded. Converts an IEnumerable to an IQueryable. (Defined by Queryable.)
	AsQueryable<T>()	Overloaded. Converts a generic IEnumerable<T> to a generic IQueryable<T>. (Defined by Queryable.)
	Average<T>(Func<T, Decimal>)	Overloaded. Computes the average of a sequence of Decimal values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.)
	Average<T>(Func<T, Nullable<Decimal>>)	Overloaded. 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. (Defined by Enumerable.)
	Average<T>(Func<T, Double>)	Overloaded. Computes the average of a sequence of Double values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.)
	Average<T>(Func<T, Nullable<Double>>)	Overloaded. 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. (Defined by Enumerable.)
	Average<T>(Func<T, Int32>)	Overloaded. Computes the average of a sequence of Int32 values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.)
	Average<T>(Func<T, Nullable<Int32>>)	Overloaded. 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. (Defined by Enumerable.)
	Average<T>(Func<T, Int64>)	Overloaded. Computes the average of a sequence of Int64 values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.)
	Average<T>(Func<T, Nullable<Int64>>)	Overloaded. 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. (Defined by Enumerable.)
	Average<T>(Func<T, Single>)	Overloaded. Computes the average of a sequence of Single values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.)
	Average<T>(Func<T, Nullable<Single>>)	Overloaded. 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. (Defined by Enumerable.)
	Cast<TResult>	Converts the elements of an IEnumerable to the specified type. (Defined by Enumerable.)
	Concat<T>	Concatenates two sequences. (Defined by Enumerable.)
	Contains<T>(T)	Overloaded. Determines whether a sequence contains a specified element by using the default equality comparer. (Defined by Enumerable.)
	Contains<T>(T, IEqualityComparer<T>)	Overloaded. Determines whether a sequence contains a specified element by using a specified IEqualityComparer<T>. (Defined by Enumerable.)
	Count<T>()	Overloaded. Returns the number of elements in a sequence. (Defined by Enumerable.)
	Count<T>(Func<T, Boolean>)	Overloaded. Returns a number that represents how many elements in the specified sequence satisfy a condition. (Defined by Enumerable.)
	DefaultIfEmpty<T>()	Overloaded. Returns the elements of the specified sequence or the type parameter's default value in a singleton collection if the sequence is empty. (Defined by Enumerable.)
	DefaultIfEmpty<T>(T)	Overloaded. Returns the elements of the specified sequence or the specified value in a singleton collection if the sequence is empty. (Defined by Enumerable.)
	Distinct<T>()	Overloaded. Returns distinct elements from a sequence by using the default equality comparer to compare values. (Defined by Enumerable.)
	Distinct<T>(IEqualityComparer<T>)	Overloaded. Returns distinct elements from a sequence by using a specified IEqualityComparer<T> to compare values. (Defined by Enumerable.)
	ElementAt<T>	Returns the element at a specified index in a sequence. (Defined by Enumerable.)
	ElementAtOrDefault<T>	Returns the element at a specified index in a sequence or a default value if the index is out of range. (Defined by Enumerable.)
	Except<T>(IEnumerable<T>)	Overloaded. Produces the set difference of two sequences by using the default equality comparer to compare values. (Defined by Enumerable.)
	Except<T>(IEnumerable<T>, IEqualityComparer<T>)	Overloaded. Produces the set difference of two sequences by using the specified IEqualityComparer<T> to compare values. (Defined by Enumerable.)
	First<T>()	Overloaded. Returns the first element of a sequence. (Defined by Enumerable.)
	First<T>(Func<T, Boolean>)	Overloaded. Returns the first element in a sequence that satisfies a specified condition. (Defined by Enumerable.)
	FirstOrDefault<T>()	Overloaded. Returns the first element of a sequence, or a default value if the sequence contains no elements. (Defined by Enumerable.)
	FirstOrDefault<T>(Func<T, Boolean>)	Overloaded. Returns the first element of the sequence that satisfies a condition or a default value if no such element is found. (Defined by Enumerable.)
	GroupBy<T, TKey>(Func<T, TKey>)	Overloaded. Groups the elements of a sequence according to a specified key selector function. (Defined by Enumerable.)
	GroupBy<T, TKey>(Func<T, TKey>, IEqualityComparer<TKey>)	Overloaded. Groups the elements of a sequence according to a specified key selector function and compares the keys by using a specified comparer. (Defined by Enumerable.)
	GroupBy<T, TKey, TElement>(Func<T, TKey>, Func<T, TElement>)	Overloaded. 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. (Defined by Enumerable.)
	GroupBy<T, TKey, TResult>(Func<T, TKey>, Func<TKey, IEnumerable<T>, TResult>)	Overloaded. Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. (Defined by Enumerable.)
	GroupBy<T, TKey, TElement>(Func<T, TKey>, Func<T, TElement>, IEqualityComparer<TKey>)	Overloaded. 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. (Defined by Enumerable.)
	GroupBy<T, TKey, TResult>(Func<T, TKey>, Func<TKey, IEnumerable<T>, TResult>, IEqualityComparer<TKey>)	Overloaded. 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. (Defined by Enumerable.)
	GroupBy<T, TKey, TElement, TResult>(Func<T, TKey>, Func<T, TElement>, Func<TKey, IEnumerable<TElement>, TResult>)	Overloaded. 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. (Defined by Enumerable.)
	GroupBy<T, TKey, TElement, TResult>(Func<T, TKey>, Func<T, TElement>, Func<TKey, IEnumerable<TElement>, TResult>, IEqualityComparer<TKey>)	Overloaded. 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. (Defined by Enumerable.)
	GroupJoin<T, TInner, TKey, TResult>(IEnumerable<TInner>, Func<T, TKey>, Func<TInner, TKey>, Func<T, IEnumerable<TInner>, TResult>)	Overloaded. Correlates the elements of two sequences based on equality of keys and groups the results. The default equality comparer is used to compare keys. (Defined by Enumerable.)
	GroupJoin<T, TInner, TKey, TResult>(IEnumerable<TInner>, Func<T, TKey>, Func<TInner, TKey>, Func<T, IEnumerable<TInner>, TResult>, IEqualityComparer<TKey>)	Overloaded. Correlates the elements of two sequences based on key equality and groups the results. A specified IEqualityComparer<T> is used to compare keys. (Defined by Enumerable.)
	Intersect<T>(IEnumerable<T>)	Overloaded. Produces the set intersection of two sequences by using the default equality comparer to compare values. (Defined by Enumerable.)
	Intersect<T>(IEnumerable<T>, IEqualityComparer<T>)	Overloaded. Produces the set intersection of two sequences by using the specified IEqualityComparer<T> to compare values. (Defined by Enumerable.)
	Join<T, TInner, TKey, TResult>(IEnumerable<TInner>, Func<T, TKey>, Func<TInner, TKey>, Func<T, TInner, TResult>)	Overloaded. Correlates the elements of two sequences based on matching keys. The default equality comparer is used to compare keys. (Defined by Enumerable.)
	Join<T, TInner, TKey, TResult>(IEnumerable<TInner>, Func<T, TKey>, Func<TInner, TKey>, Func<T, TInner, TResult>, IEqualityComparer<TKey>)	Overloaded. Correlates the elements of two sequences based on matching keys. A specified IEqualityComparer<T> is used to compare keys. (Defined by Enumerable.)
	Last<T>()	Overloaded. Returns the last element of a sequence. (Defined by Enumerable.)
	Last<T>(Func<T, Boolean>)	Overloaded. Returns the last element of a sequence that satisfies a specified condition. (Defined by Enumerable.)
	LastOrDefault<T>()	Overloaded. Returns the last element of a sequence, or a default value if the sequence contains no elements. (Defined by Enumerable.)
	LastOrDefault<T>(Func<T, Boolean>)	Overloaded. Returns the last element of a sequence that satisfies a condition or a default value if no such element is found. (Defined by Enumerable.)
	LongCount<T>()	Overloaded. Returns an Int64 that represents the total number of elements in a sequence. (Defined by Enumerable.)
	LongCount<T>(Func<T, Boolean>)	Overloaded. Returns an Int64 that represents how many elements in a sequence satisfy a condition. (Defined by Enumerable.)
	Max<T>()	Overloaded. Returns the maximum value in a generic sequence. (Defined by Enumerable.)
	Max<T>(Func<T, Decimal>)	Overloaded. Invokes a transform function on each element of a sequence and returns the maximum Decimal value. (Defined by Enumerable.)
	Max<T>(Func<T, Nullable<Decimal>>)	Overloaded. Invokes a transform function on each element of a sequence and returns the maximum nullable Decimal value. (Defined by Enumerable.)
	Max<T>(Func<T, Double>)	Overloaded. Invokes a transform function on each element of a sequence and returns the maximum Double value. (Defined by Enumerable.)
	Max<T>(Func<T, Nullable<Double>>)	Overloaded. Invokes a transform function on each element of a sequence and returns the maximum nullable Double value. (Defined by Enumerable.)
	Max<T>(Func<T, Int32>)	Overloaded. Invokes a transform function on each element of a sequence and returns the maximum Int32 value. (Defined by Enumerable.)
	Max<T>(Func<T, Nullable<Int32>>)	Overloaded. Invokes a transform function on each element of a sequence and returns the maximum nullable Int32 value. (Defined by Enumerable.)
	Max<T>(Func<T, Int64>)	Overloaded. Invokes a transform function on each element of a sequence and returns the maximum Int64 value. (Defined by Enumerable.)
	Max<T>(Func<T, Nullable<Int64>>)	Overloaded. Invokes a transform function on each element of a sequence and returns the maximum nullable Int64 value. (Defined by Enumerable.)
	Max<T>(Func<T, Single>)	Overloaded. Invokes a transform function on each element of a sequence and returns the maximum Single value. (Defined by Enumerable.)
	Max<T>(Func<T, Nullable<Single>>)	Overloaded. Invokes a transform function on each element of a sequence and returns the maximum nullable Single value. (Defined by Enumerable.)
	Max<T, TResult>(Func<T, TResult>)	Overloaded. Invokes a transform function on each element of a generic sequence and returns the maximum resulting value. (Defined by Enumerable.)
	Min<T>()	Overloaded. Returns the minimum value in a generic sequence. (Defined by Enumerable.)
	Min<T>(Func<T, Decimal>)	Overloaded. Invokes a transform function on each element of a sequence and returns the minimum Decimal value. (Defined by Enumerable.)
	Min<T>(Func<T, Nullable<Decimal>>)	Overloaded. Invokes a transform function on each element of a sequence and returns the minimum nullable Decimal value. (Defined by Enumerable.)
	Min<T>(Func<T, Double>)	Overloaded. Invokes a transform function on each element of a sequence and returns the minimum Double value. (Defined by Enumerable.)
	Min<T>(Func<T, Nullable<Double>>)	Overloaded. Invokes a transform function on each element of a sequence and returns the minimum nullable Double value. (Defined by Enumerable.)
	Min<T>(Func<T, Int32>)	Overloaded. Invokes a transform function on each element of a sequence and returns the minimum Int32 value. (Defined by Enumerable.)
	Min<T>(Func<T, Nullable<Int32>>)	Overloaded. Invokes a transform function on each element of a sequence and returns the minimum nullable Int32 value. (Defined by Enumerable.)
	Min<T>(Func<T, Int64>)	Overloaded. Invokes a transform function on each element of a sequence and returns the minimum Int64 value. (Defined by Enumerable.)
	Min<T>(Func<T, Nullable<Int64>>)	Overloaded. Invokes a transform function on each element of a sequence and returns the minimum nullable Int64 value. (Defined by Enumerable.)
	Min<T>(Func<T, Single>)	Overloaded. Invokes a transform function on each element of a sequence and returns the minimum Single value. (Defined by Enumerable.)
	Min<T>(Func<T, Nullable<Single>>)	Overloaded. Invokes a transform function on each element of a sequence and returns the minimum nullable Single value. (Defined by Enumerable.)
	Min<T, TResult>(Func<T, TResult>)	Overloaded. Invokes a transform function on each element of a generic sequence and returns the minimum resulting value. (Defined by Enumerable.)
	OfType<TResult>	Filters the elements of an IEnumerable based on a specified type. (Defined by Enumerable.)
	OrderBy<T, TKey>(Func<T, TKey>)	Overloaded. Sorts the elements of a sequence in ascending order according to a key. (Defined by Enumerable.)
	OrderBy<T, TKey>(Func<T, TKey>, IComparer<TKey>)	Overloaded. Sorts the elements of a sequence in ascending order by using a specified comparer. (Defined by Enumerable.)
	OrderByDescending<T, TKey>(Func<T, TKey>)	Overloaded. Sorts the elements of a sequence in descending order according to a key. (Defined by Enumerable.)
	OrderByDescending<T, TKey>(Func<T, TKey>, IComparer<TKey>)	Overloaded. Sorts the elements of a sequence in descending order by using a specified comparer. (Defined by Enumerable.)
	Reverse<T>	Inverts the order of the elements in a sequence. (Defined by Enumerable.)
	Select<T, TResult>(Func<T, TResult>)	Overloaded. Projects each element of a sequence into a new form. (Defined by Enumerable.)
	Select<T, TResult>(Func<T, Int32, TResult>)	Overloaded. Projects each element of a sequence into a new form by incorporating the element's index. (Defined by Enumerable.)
	SelectMany<T, TResult>(Func<T, IEnumerable<TResult>>)	Overloaded. Projects each element of a sequence to an IEnumerable<T> and flattens the resulting sequences into one sequence. (Defined by Enumerable.)
	SelectMany<T, TResult>(Func<T, Int32, IEnumerable<TResult>>)	Overloaded. 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. (Defined by Enumerable.)
	SelectMany<T, TCollection, TResult>(Func<T, Int32, IEnumerable<TCollection>>, Func<T, TCollection, TResult>)	Overloaded. 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. (Defined by Enumerable.)
	SelectMany<T, TCollection, TResult>(Func<T, IEnumerable<TCollection>>, Func<T, TCollection, TResult>)	Overloaded. 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. (Defined by Enumerable.)
	SequenceEqual<T>(IEnumerable<T>)	Overloaded. Determines whether two sequences are equal by comparing the elements by using the default equality comparer for their type. (Defined by Enumerable.)
	SequenceEqual<T>(IEnumerable<T>, IEqualityComparer<T>)	Overloaded. Determines whether two sequences are equal by comparing their elements by using a specified IEqualityComparer<T>. (Defined by Enumerable.)
	Single<T>()	Overloaded. Returns the only element of a sequence, and throws an exception if there is not exactly one element in the sequence. (Defined by Enumerable.)
	Single<T>(Func<T, Boolean>)	Overloaded. Returns the only element of a sequence that satisfies a specified condition, and throws an exception if more than one such element exists. (Defined by Enumerable.)
	SingleOrDefault<T>()	Overloaded. 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. (Defined by Enumerable.)
	SingleOrDefault<T>(Func<T, Boolean>)	Overloaded. 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. (Defined by Enumerable.)
	Skip<T>	Bypasses a specified number of elements in a sequence and then returns the remaining elements. (Defined by Enumerable.)
	SkipWhile<T>(Func<T, Boolean>)	Overloaded. Bypasses elements in a sequence as long as a specified condition is true and then returns the remaining elements. (Defined by Enumerable.)
	SkipWhile<T>(Func<T, Int32, Boolean>)	Overloaded. 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. (Defined by Enumerable.)
	Sum<T>(Func<T, Decimal>)	Overloaded. Computes the sum of the sequence of Decimal values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.)
	Sum<T>(Func<T, Nullable<Decimal>>)	Overloaded. 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. (Defined by Enumerable.)
	Sum<T>(Func<T, Double>)	Overloaded. Computes the sum of the sequence of Double values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.)
	Sum<T>(Func<T, Nullable<Double>>)	Overloaded. 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. (Defined by Enumerable.)
	Sum<T>(Func<T, Int32>)	Overloaded. Computes the sum of the sequence of Int32 values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.)
	Sum<T>(Func<T, Nullable<Int32>>)	Overloaded. 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. (Defined by Enumerable.)
	Sum<T>(Func<T, Int64>)	Overloaded. Computes the sum of the sequence of Int64 values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.)
	Sum<T>(Func<T, Nullable<Int64>>)	Overloaded. 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. (Defined by Enumerable.)
	Sum<T>(Func<T, Single>)	Overloaded. Computes the sum of the sequence of Single values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.)
	Sum<T>(Func<T, Nullable<Single>>)	Overloaded. 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. (Defined by Enumerable.)
	Take<T>	Returns a specified number of contiguous elements from the start of a sequence. (Defined by Enumerable.)
	TakeWhile<T>(Func<T, Boolean>)	Overloaded. Returns elements from a sequence as long as a specified condition is true. (Defined by Enumerable.)
	TakeWhile<T>(Func<T, Int32, Boolean>)	Overloaded. 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. (Defined by Enumerable.)
	ToArray<T>	Creates an array from a IEnumerable<T>. (Defined by Enumerable.)
	ToDictionary<T, TKey>(Func<T, TKey>)	Overloaded. Creates a Dictionary<TKey, TValue> from an IEnumerable<T> according to a specified key selector function. (Defined by Enumerable.)
	ToDictionary<T, TKey>(Func<T, TKey>, IEqualityComparer<TKey>)	Overloaded. Creates a Dictionary<TKey, TValue> from an IEnumerable<T> according to a specified key selector function and key comparer. (Defined by Enumerable.)
	ToDictionary<T, TKey, TElement>(Func<T, TKey>, Func<T, TElement>)	Overloaded. Creates a Dictionary<TKey, TValue> from an IEnumerable<T> according to specified key selector and element selector functions. (Defined by Enumerable.)
	ToDictionary<T, TKey, TElement>(Func<T, TKey>, Func<T, TElement>, IEqualityComparer<TKey>)	Overloaded. Creates a Dictionary<TKey, TValue> from an IEnumerable<T> according to a specified key selector function, a comparer, and an element selector function. (Defined by Enumerable.)
	ToList<T>	Creates a List<T> from an IEnumerable<T>. (Defined by Enumerable.)
	ToLookup<T, TKey>(Func<T, TKey>)	Overloaded. Creates a Lookup<TKey, TElement> from an IEnumerable<T> according to a specified key selector function. (Defined by Enumerable.)
	ToLookup<T, TKey>(Func<T, TKey>, IEqualityComparer<TKey>)	Overloaded. Creates a Lookup<TKey, TElement> from an IEnumerable<T> according to a specified key selector function and key comparer. (Defined by Enumerable.)
	ToLookup<T, TKey, TElement>(Func<T, TKey>, Func<T, TElement>)	Overloaded. Creates a Lookup<TKey, TElement> from an IEnumerable<T> according to specified key selector and element selector functions. (Defined by Enumerable.)
	ToLookup<T, TKey, TElement>(Func<T, TKey>, Func<T, TElement>, IEqualityComparer<TKey>)	Overloaded. Creates a Lookup<TKey, TElement> from an IEnumerable<T> according to a specified key selector function, a comparer and an element selector function. (Defined by Enumerable.)
	Union<T>(IEnumerable<T>)	Overloaded. Produces the set union of two sequences by using the default equality comparer. (Defined by Enumerable.)
	Union<T>(IEnumerable<T>, IEqualityComparer<T>)	Overloaded. Produces the set union of two sequences by using a specified IEqualityComparer<T>. (Defined by Enumerable.)
	Where<T>(Func<T, Boolean>)	Overloaded. Filters a sequence of values based on a predicate. (Defined by Enumerable.)
	Where<T>(Func<T, Int32, Boolean>)	Overloaded. Filters a sequence of values based on a predicate. Each element's index is used in the logic of the predicate function. (Defined by Enumerable.)
	Zip<T, TSecond, TResult>	Merges two sequences by using the specified predicate function. (Defined by Enumerable.)

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Explicit Interface Implementations

	Name	Description
	ICollection.CopyTo	Copies the elements of the ICollection to an Array, starting at a particular Array index.
	ICollection<T>.IsReadOnly	Gets a value indicating whether the ICollection<T> is read-only.
	ICollection.IsSynchronized	Gets a value indicating whether access to the ICollection is synchronized (thread safe).
	ICollection.SyncRoot	Gets an object that can be used to synchronize access to the ICollection.
	IEnumerable<T>.GetEnumerator	Returns an enumerator that iterates through a collection.
	IEnumerable.GetEnumerator	Returns an enumerator that iterates through a collection.
	IList.Add	Adds an item to the IList.
	IList.Contains	Determines whether the IList contains a specific value.
	IList.IndexOf	Determines the index of a specific item in the IList.
	IList.Insert	Inserts an item to the IList at the specified index.
	IList.IsFixedSize	Gets a value indicating whether the IList has a fixed size.
	IList.IsReadOnly	Gets a value indicating whether the IList is read-only.
	IList.Item	Gets or sets the element at the specified index.
	IList.Remove	Removes the first occurrence of a specific object from the IList.

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Remarks

This class implements the IList<T> generic interface using an array whose size is dynamically increased as required.

The List<T> class uses both an equality comparer and an ordering comparer.

Methods such as Contains, IndexOf, LastIndexOf, and Remove use an equality comparer for the list elements. The default equality comparer for type T is determined as follows. If type T implements the IEquatable<T> generic interface, then the equality comparer is the Equals(T) method of that interface; otherwise, the default equality comparer is Object.Equals(Object).
Methods such as BinarySearch and Sort use an ordering comparer for the list elements. The default comparer for type T is determined as follows. If type T implements the IComparable<T> generic interface, then the default comparer is the CompareTo(T) method of that interface; otherwise, if type T implements the nongeneric IComparable interface, then the default comparer is the CompareTo(Object) method of that interface. If type T implements neither interface, then there is no default comparer, and a comparer or comparison delegate must be provided explicitly.

The List<T> is not guaranteed to be sorted. You must sort the List<T> before performing operations (such as BinarySearch) that require the List<T> to be sorted.

Elements in this collection can be accessed using an integer index. Indexes in this collection are zero-based.

List<T> accepts nulla null reference (Nothing in Visual Basic) as a valid value for reference types and allows duplicate elements.

Using LINQ

To conserve resources for Silverlight-based applications, the List<T> class in the .NET Framework for Silverlight class library does not include all the methods in the full .NET Framework, because the functionality of these methods is available with LINQ. For more information about LINQ, see LINQ to Objects.

The following examples show how to use LINQ to obtain the functionality of the methods that are not provided in the List<T> class.

These examples operate on a collection of integers.

Dim numbers As List(Of Integer) = _
    New List(Of Integer)(New Integer() {1, 2, 3, 4, 5, 6, 7, 8, 9})

List<int> numbers = new List<int> { 1, 2, 3, 4, 5, 6, 7, 8, 9 };

ConvertAll Functionality

This LINQ code creates a collection of strings that are converted from the numbers collection.

Dim strings As List(Of String) = numbers.Select(Function(n) n.ToString()).ToList()

List<string> strings = numbers.Select(n => n.ToString()).ToList();

Exists Functionality

This LINQ code returns true if any value in the numbers collection is greater than or equal to 10.

Dim found As Boolean = numbers.Any(Function(n) n >= 10)

bool found = numbers.Any(n => n >= 10);

Find Functionality

This LINQ code returns the first even number in the numbers collection.

Dim firstEven As Integer = numbers.First(Function(n) n Mod 2 = 0)

int firstEven = numbers.First(n => n % 2 == 0);

FindAll Functionality

This LINQ code creates a collection of even numbers from the numbers collection.

Dim evenNums As List(Of Integer) = numbers.Where(Function(n) n Mod 2 = 0).ToList()

List<int> evenNums = numbers.Where(n => n % 2 == 0).ToList();

FindIndex Functionality

This code finds the index of the first even number in the numbers collection. It is more efficient to iterate through the collection to find the index value than to use LINQ.

Dim index As Integer = -1
Dim i As Integer = 0
Do While i < numbers.Count
    If numbers(i) Mod 2 = 0 Then
        index = i
        Exit Do
    End If
    i += 1
Loop

' LINQ
Dim ix = numbers.Select(Function(n, x) New With {.Number = n, .Index = x}).Where(Function(n) n.Number Mod 2 = 0).Select(Function(n) n.Index).First()

int index = -1;
for (int i = 0; i < numbers.Count; i++)
{
    if (numbers[i] % 2 == 0)
    {
        index = i;
        break;
    }
}

// LINQ
int ix = numbers.Select((n, i) => new { Number = n, Index = i }).Where(n => n.Number % 2 == 0).Select(n => n.Index).First();

FindLastIndex Functionality

This code finds the index of the last even number in the numbers collection. It is more efficient to iterate through the collection to find the index value than to use LINQ. In this example, the iteration is from the end of the collection to the beginning.

Dim lastIndex As Integer = -1
Dim z As Integer = numbers.Count - 1
Do While z >= 0
    If numbers(z) Mod 2 = 0 Then
        lastIndex = z
        Exit Do
    End If
    z -= 1
Loop

' In LINQ
Dim lix = numbers.Select(Function(n, x) New With {.Number = n, .Index = x}).Where(Function(n) n.Number Mod 2 = 0).Select(Function(n) n.Index).Last()

int lastIndex = -1;
for (int i = numbers.Count - 1; i >= 0; i--)
{
    if (numbers[i] % 2 == 0)
    {
        lastIndex = i;
        break;
    }
}

// In LINQ
int lix = numbers.Select((n, i) => new { Number = n, Index = i }).Where(n => n.Number % 2 == 0).Select(n => n.Index).Last();

RemoveAll Functionality

This LINQ code removes odd numbers from the numbers collection. The result is another collection that is also named numbers.

numbers = numbers.Where(Function(n) Not (n Mod 2 = 0)).ToList()

numbers = numbers.Where(n => !(n % 2 == 0)).ToList();

Examples

There are two examples for this class. This first example shows how to create an object derived from the List<T> class for binding data to a ListBox control. The binding in this example is one-way; see Data Binding for a discussion of other binding options and scenarios.

The Canada class derives from the List<T> class and its constructor populates the list with data. Add this class to the partial MainPage class of your project.

Public Class Canada
    Inherits List(Of String)
    Public Sub New()
        MyBase.New()
        Add("Alberta")
        Add("British Columbia")
        Add("Manitoba")
        Add("New Brunswick")
        Add("Newfoundland")
        Add("Northwest Territories")
        Add("Nova Scotia")
        Add("Nunavut")
        Add("Ontario")
        Add("Prince Edward Island")
        Add("Quebec")
        Add("Yukon")
    End Sub
End Class

// Be sure this class within the
// C# namespace of Page.xaml.cs.
public class Canada : List<string>
{
    public Canada()
    {
        Add("Alberta");
        Add("British Columbia");
        Add("Manitoba");
        Add("New Brunswick");
        Add("Newfoundland");
        Add("Northwest Territories");
        Add("Nova Scotia");
        Add("Nunavut");
        Add("Ontario");
        Add("Prince Edward Island");
        Add("Quebec");
        Add("Yukon");
    }
}

The following XAML references and elements perform the data binding:

xmlns:src="clr-namespace:ListDemoCS"

This is a reference to the common language runtime (CLR) namespace, which is automatically declared within the assembly and exposes its public types. Replace ListDemoCS with the name of your assembly (project name).
<src:Canada x:Name="CanadaList"/>

This is a resource dictionary reference specified in the <Grid.Resources> element. It specifies the object to bind to (Canada) and its name (CanadaList) is specified by controls, such as a ListBox control, that use this resource.
<ListBox x:Name="ListCanada" ItemsSource="{Binding Source={StaticResource CanadaList}}"/>

This element defines a ListBox control with the ItemsSource property set to the bound object.

The complete XAML is as follows.

 <UserControl x:Class="ListDemoCS.Page"
    xmlns="https://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x="https://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:src="clr-namespace:ListDemoCS"
    Width="400" Height="300">
    <Grid x:Name="LayoutRoot" Background="White">
        <Grid.Resources>
            <src:Canada x:Name="CanadaList"/>
        </Grid.Resources>
        <ListBox x:Name="ListCanada"  ItemsSource="{Binding Source={StaticResource CanadaList}}"/>
    </Grid>
</UserControl>

The next example demonstrates several properties and methods of the List<T> generic class. The default constructor is used to create a list of strings with the default capacity. The Capacity property is displayed and then the Add method is used to add several items. The items are listed, and the Capacity property is displayed again, along with the Count property, to show that the capacity has been increased as needed.

The Contains method is used to test for the presence of an item in the list, the Insert method is used to insert a new item in the middle of the list, and the contents of the list are displayed again.

The default Item property (the indexer in C#) is used to retrieve an item, the Remove method is used to remove the first instance of the duplicate item added earlier, and the contents are displayed again. The Remove method always removes the first instance it encounters.

The TrimExcess method is used to reduce the capacity to match the count, and the Capacity and Count properties are displayed. If the unused capacity had been less than 10 percent of total capacity, the list would not have been resized.

Finally, the Clear method is used to remove all items from the list, and the Capacity and Count properties are displayed.

Note:
To run this example, see Building Examples That Use a Demo Method and a TextBlock Control.

Imports System.Collections.Generic

Public Class Example

   Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)

      Dim dinosaurs As New List(Of String)

      outputBlock.Text &= String.Format(vbLf & "Capacity: {0}", dinosaurs.Capacity) & vbCrLf

      dinosaurs.Add("Tyrannosaurus")
      dinosaurs.Add("Amargasaurus")
      dinosaurs.Add("Mamenchisaurus")
      dinosaurs.Add("Deinonychus")
      dinosaurs.Add("Compsognathus")

      outputBlock.Text &= vbCrLf
      For Each dinosaur As String In dinosaurs
         outputBlock.Text &= dinosaur & vbCrLf
      Next

      outputBlock.Text &= String.Format(vbLf & "Capacity: {0}", dinosaurs.Capacity) & vbCrLf
      outputBlock.Text &= String.Format("Count: {0}", dinosaurs.Count) & vbCrLf

      outputBlock.Text &= vbLf & String.Format("Contains(""Deinonychus"": {0}", _
          dinosaurs.Contains("Deinonychus")) & vbCrLf

      outputBlock.Text &= String.Format(vbLf & "Insert(2, ""Compsognathus"")") & vbCrLf
      dinosaurs.Insert(2, "Compsognathus")

      outputBlock.Text &= vbCrLf
      For Each dinosaur As String In dinosaurs
         outputBlock.Text &= dinosaur & vbCrLf
      Next

      outputBlock.Text &= String.Format(vbLf & "dinosaurs(3): {0}", dinosaurs(3)) & vbCrLf

      outputBlock.Text &= vbLf & "Remove(""Compsognathus"")" & vbCrLf
      dinosaurs.Remove("Compsognathus")

      outputBlock.Text &= vbCrLf
      For Each dinosaur As String In dinosaurs
         outputBlock.Text &= dinosaur & vbCrLf
      Next

      dinosaurs.TrimExcess()
      outputBlock.Text &= vbLf & "TrimExcess()" & vbCrLf
      outputBlock.Text &= String.Format("Capacity: {0}", dinosaurs.Capacity) & vbCrLf
      outputBlock.Text &= String.Format("Count: {0}", dinosaurs.Count) & vbCrLf

      dinosaurs.Clear()
      outputBlock.Text &= vbLf & "Clear()" & vbCrLf
      outputBlock.Text &= String.Format("Capacity: {0}", dinosaurs.Capacity) & vbCrLf
      outputBlock.Text &= String.Format("Count: {0}", dinosaurs.Count) & vbCrLf
   End Sub
End Class

' This code example produces the following output:
'
'Capacity: 0
'
'Tyrannosaurus
'Amargasaurus
'Mamenchisaurus
'Deinonychus
'Compsognathus
'
'Capacity: 8
'Count: 5
'
'Contains("Deinonychus"): True
'
'Insert(2, "Compsognathus")
'
'Tyrannosaurus
'Amargasaurus
'Compsognathus
'Mamenchisaurus
'Deinonychus
'Compsognathus
'
'dinosaurs(3): Mamenchisaurus
'
'Remove("Compsognathus")
'
'Tyrannosaurus
'Amargasaurus
'Mamenchisaurus
'Deinonychus
'Compsognathus
'
'TrimExcess()
'Capacity: 5
'Count: 5
'
'Clear()
'Capacity: 5
'Count: 0

using System;
using System.Collections.Generic;

public class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      List<string> dinosaurs = new List<string>();

      outputBlock.Text += String.Format("\nCapacity: {0}", dinosaurs.Capacity) + "\n";

      dinosaurs.Add("Tyrannosaurus");
      dinosaurs.Add("Amargasaurus");
      dinosaurs.Add("Mamenchisaurus");
      dinosaurs.Add("Deinonychus");
      dinosaurs.Add("Compsognathus");

      outputBlock.Text += "\n";
      foreach (string dinosaur in dinosaurs)
      {
         outputBlock.Text += dinosaur + "\n";
      }

      outputBlock.Text += String.Format("\nCapacity: {0}", dinosaurs.Capacity) + "\n";
      outputBlock.Text += String.Format("Count: {0}", dinosaurs.Count) + "\n";

      outputBlock.Text += String.Format("\nContains(\"Deinonychus\"): {0}",
          dinosaurs.Contains("Deinonychus")) + "\n";

      outputBlock.Text += String.Format("\nInsert(2, \"Compsognathus\")") + "\n";
      dinosaurs.Insert(2, "Compsognathus");

      outputBlock.Text += "\n";
      foreach (string dinosaur in dinosaurs)
      {
         outputBlock.Text += dinosaur + "\n";
      }

      outputBlock.Text += String.Format("\ndinosaurs[3]: {0}", dinosaurs[3]) + "\n";

      outputBlock.Text += "\nRemove(\"Compsognathus\")" + "\n";
      dinosaurs.Remove("Compsognathus");

      outputBlock.Text += "\n";
      foreach (string dinosaur in dinosaurs)
      {
         outputBlock.Text += dinosaur + "\n";
      }

      dinosaurs.TrimExcess();
      outputBlock.Text += "\nTrimExcess()" + "\n";
      outputBlock.Text += String.Format("Capacity: {0}", dinosaurs.Capacity) + "\n";
      outputBlock.Text += String.Format("Count: {0}", dinosaurs.Count) + "\n";

      dinosaurs.Clear();
      outputBlock.Text += "\nClear()" + "\n";
      outputBlock.Text += String.Format("Capacity: {0}", dinosaurs.Capacity) + "\n";
      outputBlock.Text += String.Format("Count: {0}", dinosaurs.Count) + "\n";
   }
}

/* This code example produces the following output:

Capacity: 0

Tyrannosaurus
Amargasaurus
Mamenchisaurus
Deinonychus
Compsognathus

Capacity: 8
Count: 5

Contains("Deinonychus"): True

Insert(2, "Compsognathus")

Tyrannosaurus
Amargasaurus
Compsognathus
Mamenchisaurus
Deinonychus
Compsognathus

dinosaurs[3]: Mamenchisaurus

Remove("Compsognathus")

Tyrannosaurus
Amargasaurus
Mamenchisaurus
Deinonychus
Compsognathus

TrimExcess()
Capacity: 5
Count: 5

Clear()
Capacity: 5
Count: 0
 */

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

Thread Safety

Public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

A List<T> can support multiple readers concurrently, as long as the collection is not modified. Enumerating through a collection is intrinsically not a thread-safe procedure. In the rare case where an enumeration contends with one or more write accesses, the only way to ensure thread safety is to lock the collection during the entire enumeration. To allow the collection to be accessed by multiple threads for reading and writing, you must implement your own synchronization.

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