StringCollection Class

Definition

Namespace:

System.Collections.Specialized

Assembly:

System.Collections.Specialized.dll

Source:

StringCollection.cs

Represents a collection of strings.

public ref class StringCollection : System::Collections::IList

public class StringCollection : System.Collections.IList

type StringCollection = class
    interface ICollection
    interface IEnumerable
    interface IList

Public Class StringCollection
Implements IList

Inheritance

Object

StringCollection

Derived

System.Configuration.CommaDelimitedStringCollection

Implements

ICollection IEnumerable IList

Examples

The following code example demonstrates several of the properties and methods of StringCollection.

#using <System.dll>

using namespace System;
using namespace System::Collections;
using namespace System::Collections::Specialized;

void PrintValues1( StringCollection^ myCol );
void PrintValues2( StringCollection^ myCol );
void PrintValues3( StringCollection^ myCol );

int main()
{
   
   // Create and initializes a new StringCollection.
   StringCollection^ myCol = gcnew StringCollection;
   
   // Add a range of elements from an array to the end of the StringCollection.
   array<String^>^myArr = {"RED","orange","yellow","RED","green","blue","RED","indigo","violet","RED"};
   myCol->AddRange( myArr );
   
   // Display the contents of the collection using for each. This is the preferred method.
   Console::WriteLine( "Displays the elements using for each:" );
   PrintValues1( myCol );

   // Display the contents of the collection using the enumerator.
   Console::WriteLine( "Displays the elements using the IEnumerator:" );
   PrintValues2( myCol );
   
   // Display the contents of the collection using the Count and Item properties.
   Console::WriteLine( "Displays the elements using the Count and Item properties:" );
   PrintValues3( myCol );
   
   // Add one element to the end of the StringCollection and insert another at index 3.
   myCol->Add( "* white" );
   myCol->Insert( 3, "* gray" );
   Console::WriteLine( "After adding \"* white\" to the end and inserting \"* gray\" at index 3:" );
   PrintValues1( myCol );
   
   // Remove one element from the StringCollection.
   myCol->Remove( "yellow" );
   Console::WriteLine( "After removing \"yellow\":" );
   PrintValues1( myCol );
   
   // Remove all occurrences of a value from the StringCollection.
   int i = myCol->IndexOf( "RED" );
   while ( i > -1 )
   {
      myCol->RemoveAt( i );
      i = myCol->IndexOf( "RED" );
   }

   
   // Verify that all occurrences of "RED" are gone.
   if ( myCol->Contains( "RED" ) )
      Console::WriteLine( "*** The collection still contains \"RED\"." );

   Console::WriteLine( "After removing all occurrences of \"RED\":" );
   PrintValues1( myCol );
   
   // Copy the collection to a new array starting at index 0.
   array<String^>^myArr2 = gcnew array<String^>(myCol->Count);
   myCol->CopyTo( myArr2, 0 );
   Console::WriteLine( "The new array contains:" );
   for ( i = 0; i < myArr2->Length; i++ )
   {
      Console::WriteLine( "   [{0}] {1}", i, myArr2[ i ] );

   }
   Console::WriteLine();
   
   // Clears the entire collection.
   myCol->Clear();
   Console::WriteLine( "After clearing the collection:" );
   PrintValues1( myCol );
}


// Uses the for each statement which hides the complexity of the enumerator.
// NOTE: The for each statement is the preferred way of enumerating the contents of a collection.
void PrintValues1( StringCollection^ myCol )  {
   for each ( Object^ obj in myCol )
      Console::WriteLine( "   {0}", obj );
   Console::WriteLine();
}

// Uses the enumerator. 
void PrintValues2( StringCollection^ myCol )
{
   StringEnumerator^ myEnumerator = myCol->GetEnumerator();
   while ( myEnumerator->MoveNext() )
      Console::WriteLine( "   {0}", myEnumerator->Current );

   Console::WriteLine();
}


// Uses the Count and Item properties.
void PrintValues3( StringCollection^ myCol )
{
   for ( int i = 0; i < myCol->Count; i++ )
      Console::WriteLine( "   {0}", myCol[ i ] );
   Console::WriteLine();
}

/*
This code produces the following output.

Displays the elements using the IEnumerator:
   RED
   orange
   yellow
   RED
   green
   blue
   RED
   indigo
   violet
   RED

Displays the elements using the Count and Item properties:
   RED
   orange
   yellow
   RED
   green
   blue
   RED
   indigo
   violet
   RED

After adding "* white" to the end and inserting "* gray" at index 3:
   RED
   orange
   yellow
   * gray
   RED
   green
   blue
   RED
   indigo
   violet
   RED
   * white

After removing "yellow":
   RED
   orange
   * gray
   RED
   green
   blue
   RED
   indigo
   violet
   RED
   * white

After removing all occurrences of "RED":
   orange
   * gray
   green
   blue
   indigo
   violet
   * white

The new array contains:
   [0] orange
   [1] * gray
   [2] green
   [3] blue
   [4] indigo
   [5] violet
   [6] * white

After clearing the collection:

*/

using System;
using System.Collections;
using System.Collections.Specialized;

public class SamplesStringCollection  {

   public static void Main()  {

      // Create and initializes a new StringCollection.
      StringCollection myCol = new StringCollection();

      // Add a range of elements from an array to the end of the StringCollection.
      String[] myArr = new String[] { "RED", "orange", "yellow", "RED", "green", "blue", "RED", "indigo", "violet", "RED" };
      myCol.AddRange( myArr );

      // Display the contents of the collection using foreach. This is the preferred method.
      Console.WriteLine( "Displays the elements using foreach:" );
      PrintValues1( myCol );

      // Display the contents of the collection using the enumerator.
      Console.WriteLine( "Displays the elements using the IEnumerator:" );
      PrintValues2( myCol );

      // Display the contents of the collection using the Count and Item properties.
      Console.WriteLine( "Displays the elements using the Count and Item properties:" );
      PrintValues3( myCol );

      // Add one element to the end of the StringCollection and insert another at index 3.
      myCol.Add( "* white" );
      myCol.Insert( 3, "* gray" );

      Console.WriteLine( "After adding \"* white\" to the end and inserting \"* gray\" at index 3:" );
      PrintValues1( myCol );

      // Remove one element from the StringCollection.
      myCol.Remove( "yellow" );

      Console.WriteLine( "After removing \"yellow\":" );
      PrintValues1( myCol );

      // Remove all occurrences of a value from the StringCollection.
      int i = myCol.IndexOf( "RED" );
      while ( i > -1 )  {
         myCol.RemoveAt( i );
         i = myCol.IndexOf( "RED" );
      }

      // Verify that all occurrences of "RED" are gone.
      if ( myCol.Contains( "RED" ) )
         Console.WriteLine( "*** The collection still contains \"RED\"." );

      Console.WriteLine( "After removing all occurrences of \"RED\":" );
      PrintValues1( myCol );

      // Copy the collection to a new array starting at index 0.
      String[] myArr2 = new String[myCol.Count];
      myCol.CopyTo( myArr2, 0 );

      Console.WriteLine( "The new array contains:" );
      for ( i = 0; i < myArr2.Length; i++ )  {
         Console.WriteLine( "   [{0}] {1}", i, myArr2[i] );
      }
      Console.WriteLine();

      // Clears the entire collection.
      myCol.Clear();

      Console.WriteLine( "After clearing the collection:" );
      PrintValues1( myCol );
   }

   // Uses the foreach statement which hides the complexity of the enumerator.
   // NOTE: The foreach statement is the preferred way of enumerating the contents of a collection.
   public static void PrintValues1( StringCollection myCol )  {
      foreach ( Object obj in myCol )
         Console.WriteLine( "   {0}", obj );
      Console.WriteLine();
   }

   // Uses the enumerator.
   // NOTE: The foreach statement is the preferred way of enumerating the contents of a collection.
   public static void PrintValues2( StringCollection myCol )  {
      StringEnumerator myEnumerator = myCol.GetEnumerator();
      while ( myEnumerator.MoveNext() )
         Console.WriteLine( "   {0}", myEnumerator.Current );
      Console.WriteLine();
   }

   // Uses the Count and Item properties.
   public static void PrintValues3( StringCollection myCol )  {
      for ( int i = 0; i < myCol.Count; i++ )
         Console.WriteLine( "   {0}", myCol[i] );
      Console.WriteLine();
   }
}

/*
This code produces the following output.

Displays the elements using foreach:
   RED
   orange
   yellow
   RED
   green
   blue
   RED
   indigo
   violet
   RED

Displays the elements using the IEnumerator:
   RED
   orange
   yellow
   RED
   green
   blue
   RED
   indigo
   violet
   RED

Displays the elements using the Count and Item properties:
   RED
   orange
   yellow
   RED
   green
   blue
   RED
   indigo
   violet
   RED

After adding "* white" to the end and inserting "* gray" at index 3:
   RED
   orange
   yellow
   * gray
   RED
   green
   blue
   RED
   indigo
   violet
   RED
   * white

After removing "yellow":
   RED
   orange
   * gray
   RED
   green
   blue
   RED
   indigo
   violet
   RED
   * white

After removing all occurrences of "RED":
   orange
   * gray
   green
   blue
   indigo
   violet
   * white

The new array contains:
   [0] orange
   [1] * gray
   [2] green
   [3] blue
   [4] indigo
   [5] violet
   [6] * white

After clearing the collection:

*/

Imports System.Collections
Imports System.Collections.Specialized

Public Class SamplesStringCollection

   Public Shared Sub Main()

      ' Create and initializes a new StringCollection.
      Dim myCol As New StringCollection()

      ' Add a range of elements from an array to the end of the StringCollection.
      Dim myArr() As String = {"RED", "orange", "yellow", "RED", "green", "blue", "RED", "indigo", "violet", "RED"}
      myCol.AddRange(myArr)

      ' Display the contents of the collection using foreach. This is the preferred method.
      Console.WriteLine("Displays the elements using foreach:")
      PrintValues1(myCol)

      ' Display the contents of the collection using the enumerator.
      Console.WriteLine("Displays the elements using the IEnumerator:")
      PrintValues2(myCol)

      ' Display the contents of the collection using the Count and Item properties.
      Console.WriteLine("Displays the elements using the Count and Item properties:")
      PrintValues3(myCol)

      ' Add one element to the end of the StringCollection and insert another at index 3.
      myCol.Add("* white")
      myCol.Insert(3, "* gray")

      Console.WriteLine("After adding ""* white"" to the end and inserting ""* gray"" at index 3:")
      PrintValues1(myCol)

      ' Remove one element from the StringCollection.
      myCol.Remove("yellow")

      Console.WriteLine("After removing ""yellow"":")
      PrintValues1(myCol)

      ' Remove all occurrences of a value from the StringCollection.
      Dim i As Integer = myCol.IndexOf("RED")
      While i > - 1
         myCol.RemoveAt(i)
         i = myCol.IndexOf("RED")
      End While

      ' Verify that all occurrences of "RED" are gone.
      If myCol.Contains("RED") Then
         Console.WriteLine("*** The collection still contains ""RED"".")
      End If 
      Console.WriteLine("After removing all occurrences of ""RED"":")
      PrintValues1(myCol)

      ' Copy the collection to a new array starting at index 0.
      Dim myArr2(myCol.Count) As String
      myCol.CopyTo(myArr2, 0)

      Console.WriteLine("The new array contains:")
      For i = 0 To myArr2.Length - 1
         Console.WriteLine("   [{0}] {1}", i, myArr2(i))
      Next i
      Console.WriteLine()

      ' Clears the entire collection.
      myCol.Clear()

      Console.WriteLine("After clearing the collection:")
      PrintValues1(myCol)
   End Sub


   ' Uses the foreach statement which hides the complexity of the enumerator.
   ' NOTE: The foreach statement is the preferred way of enumerating the contents of a collection.
   Public Shared Sub PrintValues1(myCol As StringCollection)
      Dim obj As [Object]
      For Each obj In  myCol
         Console.WriteLine("   {0}", obj)
      Next obj
      Console.WriteLine()
   End Sub


   ' Uses the enumerator. 
   ' NOTE: The foreach statement is the preferred way of enumerating the contents of a collection.
   Public Shared Sub PrintValues2(myCol As StringCollection)
      Dim myEnumerator As StringEnumerator = myCol.GetEnumerator()
      While myEnumerator.MoveNext()
         Console.WriteLine("   {0}", myEnumerator.Current)
      End While
      Console.WriteLine()
   End Sub


   ' Uses the Count and Item properties.
   Public Shared Sub PrintValues3(myCol As StringCollection)
      Dim i As Integer
      For i = 0 To myCol.Count - 1
         Console.WriteLine("   {0}", myCol(i))
      Next i
      Console.WriteLine()
   End Sub

End Class


'This code produces the following output.
'
'Displays the elements using foreach:
'   RED
'   orange
'   yellow
'   RED
'   green
'   blue
'   RED
'   indigo
'   violet
'   RED
'
'Displays the elements using the IEnumerator:
'   RED
'   orange
'   yellow
'   RED
'   green
'   blue
'   RED
'   indigo
'   violet
'   RED
'
'Displays the elements using the Count and Item properties:
'   RED
'   orange
'   yellow
'   RED
'   green
'   blue
'   RED
'   indigo
'   violet
'   RED
'
'After adding "* white" to the end and inserting "* gray" at index 3:
'   RED
'   orange
'   yellow
'   * gray
'   RED
'   green
'   blue
'   RED
'   indigo
'   violet
'   RED
'   * white
'
'After removing "yellow":
'   RED
'   orange
'   * gray
'   RED
'   green
'   blue
'   RED
'   indigo
'   violet
'   RED
'   * white
'
'After removing all occurrences of "RED":
'   orange
'   * gray
'   green
'   blue
'   indigo
'   violet
'   * white
'
'The new array contains:
'   [0] orange
'   [1] * gray
'   [2] green
'   [3] blue
'   [4] indigo
'   [5] violet
'   [6] * white
'
'After clearing the collection:
'

Remarks

StringCollection accepts null as a valid value and allows duplicate elements.

String comparisons are case-sensitive.

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

Constructors

StringCollection()

Initializes a new instance of the StringCollection class.

Properties

Count	Gets the number of strings contained in the StringCollection.
IsReadOnly	Gets a value indicating whether the StringCollection is read-only.
IsSynchronized	Gets a value indicating whether access to the StringCollection is synchronized (thread safe).
Item[Int32]	Gets or sets the element at the specified index.
SyncRoot	Gets an object that can be used to synchronize access to the StringCollection.

Methods

Add(String)	Adds a string to the end of the StringCollection.
AddRange(String[])	Copies the elements of a string array to the end of the StringCollection.
Clear()	Removes all the strings from the StringCollection.
Contains(String)	Determines whether the specified string is in the StringCollection.
CopyTo(String[], Int32)	Copies the entire StringCollection values to a one-dimensional array of strings, 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)
GetEnumerator()	Returns a StringEnumerator that iterates through the StringCollection.
GetHashCode()	Serves as the default hash function. (Inherited from Object)
GetType()	Gets the Type of the current instance. (Inherited from Object)
IndexOf(String)	Searches for the specified string and returns the zero-based index of the first occurrence within the StringCollection.
Insert(Int32, String)	Inserts a string into the StringCollection at the specified index.
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
Remove(String)	Removes the first occurrence of a specific string from the StringCollection.
RemoveAt(Int32)	Removes the string at the specified index of the StringCollection.
ToString()	Returns a string that represents the current object. (Inherited from Object)

Explicit Interface Implementations

ICollection.CopyTo(Array, Int32)	Copies the entire StringCollection to a compatible one-dimensional Array, starting at the specified index of the target array.
IEnumerable.GetEnumerator()	Returns a IEnumerator that iterates through the StringCollection.
IList.Add(Object)	Adds an object to the end of the StringCollection.
IList.Contains(Object)	Determines whether an element is in the StringCollection.
IList.IndexOf(Object)	Searches for the specified Object and returns the zero-based index of the first occurrence within the entire StringCollection.
IList.Insert(Int32, Object)	Inserts an element into the StringCollection at the specified index.
IList.IsFixedSize	Gets a value indicating whether the StringCollection object has a fixed size.
IList.IsReadOnly	Gets a value indicating whether the StringCollection object is read-only.
IList.Item[Int32]	Gets or sets the element at the specified index.
IList.Remove(Object)	Removes the first occurrence of a specific object from the StringCollection.

Extension Methods

Cast<TResult>(IEnumerable)	Casts the elements of an IEnumerable to the specified type.
OfType<TResult>(IEnumerable)	Filters the elements of an IEnumerable based on a specified type.
AsParallel(IEnumerable)	Enables parallelization of a query.
AsQueryable(IEnumerable)	Converts an IEnumerable to an IQueryable.

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.

This implementation does not provide a synchronized (thread safe) wrapper for a StringCollection, but derived classes can create their own synchronized versions of the StringCollection using the SyncRoot property.

Enumerating through a collection is intrinsically not a thread safe procedure. Even when a collection is synchronized, other threads can still modify the collection, which causes the enumerator to throw an exception. To guarantee thread safety during enumeration, you can either lock the collection during the entire enumeration or catch the exceptions resulting from changes made by other threads.

See also

• Performing Culture-Insensitive String Operations