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Dictionary<TKey, TValue>.ICollection<KeyValuePair<TKey, TValue>>.Contains Method

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Determines whether the ICollection<T> contains a specific key and value.

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

Syntax

'Declaration
Private Function Contains ( _
    keyValuePair As KeyValuePair(Of TKey, TValue) _
) As Boolean Implements ICollection(Of KeyValuePair(Of TKey, TValue)).Contains

bool ICollection<KeyValuePair<TKey, TValue>>.Contains(
    KeyValuePair<TKey, TValue> keyValuePair
)

Parameters

Return Value

Type: System.Boolean
true if keyValuePair is found in the ICollection<T>; otherwise, false.

Implements

ICollection<T>.Contains(T)

Remarks

This method determines equality using the default equality comparer EqualityComparer<T>.Default for the System.Collections.Generic.KeyValuePair<TKey, TValue> structure.

This method approaches an O(1) operation.

Examples

The following example shows how to use explicit interface implementations of the System.Collections.Generic.ICollection<T> generic interface to manipulate a Dictionary<TKey, TValue> object.

Imports System.Collections.Generic

Public Class Example

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

      ' Create a new dictionary of strings, with string keys, and
      ' access it through the generic ICollection interface. The
      ' generic ICollection interface views the dictionary as a
      ' collection of KeyValuePair objects with the same type
      ' arguments as the dictionary.
      '
      Dim openWith As ICollection(Of KeyValuePair(Of String, String)) _
          = New Dictionary(Of String, String)

      ' Add some elements to the dictionary. When elements are 
      ' added through the ICollection(Of T) interface, the keys
      ' and values must be wrapped in KeyValuePair objects.
      '
      openWith.Add(New KeyValuePair(Of String, String)("txt", "notepad.exe"))
      openWith.Add(New KeyValuePair(Of String, String)("bmp", "paint.exe"))
      openWith.Add(New KeyValuePair(Of String, String)("dib", "paint.exe"))
      openWith.Add(New KeyValuePair(Of String, String)("rtf", "wordpad.exe"))

      outputBlock.Text &= vbCrLf
      For Each element As KeyValuePair(Of String, String) In openWith
         outputBlock.Text &= String.Format("{0}, {1}", element.Key, element.Value) & vbCrLf
      Next

      ' The Contains method also takes a KeyValuePair object.
      '
      outputBlock.Text &= String.Format(vbLf & _
          "Contains(KeyValuePair(""txt"", ""notepad.exe"")): {0}", _
          openWith.Contains(New KeyValuePair(Of String, String)("txt", "notepad.exe"))) & vbCrLf

      ' The Remove method takes a KeyValuePair object.)
      '
      ' Use the Remove method to remove a key/value pair.
      outputBlock.Text &= String.Format(vbLf & _
          "Remove(New KeyValuePair(""dib"", ""paint.exe""))") & vbCrLf
      openWith.Remove(New KeyValuePair(Of String, String)("dib", "paint.exe"))

      outputBlock.Text &= vbCrLf
      For Each element As KeyValuePair(Of String, String) In openWith
         outputBlock.Text &= String.Format("{0}, {1}", element.Key, element.Value) & vbCrLf
      Next

      ' Create an array of KeyValuePair objects and copy the 
      ' contents of the dictionary to it. Subtract one from the
      ' array size because Visual Basic allocates an extra array
      ' element.
      Dim copy(openWith.Count - 1) As KeyValuePair(Of String, String)
      openWith.CopyTo(copy, 0)

      ' List the contents of the array.
      '
      outputBlock.Text &= vbCrLf
      For Each element As KeyValuePair(Of String, String) In copy
         outputBlock.Text &= String.Format("{0}, {1}", element.Key, element.Value) & vbCrLf
      Next

   End Sub

End Class

' This code example produces the following output:
'
'txt, notepad.exe
'bmp, paint.exe
'dib, paint.exe
'rtf, wordpad.exe
'
'Contains(KeyValuePair("txt", "notepad.exe")): True
'
'Remove(New KeyValuePair("dib", "paint.exe"))
'
'txt, notepad.exe
'bmp, paint.exe
'rtf, wordpad.exe
'
'txt, notepad.exe
'bmp, paint.exe
'rtf, wordpad.exe 

using System;
using System.Collections.Generic;

public class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      // Create a new dictionary of strings, with string keys, and
      // access it through the generic ICollection interface. The
      // generic ICollection interface views the dictionary as a
      // collection of KeyValuePair objects with the same type
      // arguments as the dictionary.
      //
      ICollection<KeyValuePair<String, String>> openWith =
          new Dictionary<String, String>();

      // Add some elements to the dictionary. When elements are 
      // added through the ICollection<T> interface, the keys
      // and values must be wrapped in KeyValuePair objects.
      //
      openWith.Add(new KeyValuePair<String, String>("txt", "notepad.exe"));
      openWith.Add(new KeyValuePair<String, String>("bmp", "paint.exe"));
      openWith.Add(new KeyValuePair<String, String>("dib", "paint.exe"));
      openWith.Add(new KeyValuePair<String, String>("rtf", "wordpad.exe"));

      outputBlock.Text += "\n";
      foreach (KeyValuePair<string, string> element in openWith)
      {
         outputBlock.Text += String.Format("{0}, {1}", element.Key, element.Value) + "\n";
      }

      // The Contains method also takes a KeyValuePair object.
      //
      outputBlock.Text += String.Format(
          "\nContains(KeyValuePair(\"txt\", \"notepad.exe\")): {0}",
          openWith.Contains(new KeyValuePair<String, String>("txt", "notepad.exe"))) + "\n";

      // The Remove method takes a KeyValuePair object.)
      //
      // Use the Remove method to remove a key/value pair.
      outputBlock.Text += String.Format("\nRemove(new KeyValuePair(\"dib\", \"paint.exe\"))") + "\n";
      openWith.Remove(new KeyValuePair<String, String>("dib", "paint.exe"));

      outputBlock.Text += "\n";
      foreach (KeyValuePair<string, string> element in openWith)
      {
         outputBlock.Text += String.Format("{0}, {1}", element.Key, element.Value) + "\n";
      }

      // Create an array of KeyValuePair objects and copy the 
      // contents of the dictionary to it. 
      // 
      KeyValuePair<string, string>[] copy =
          new KeyValuePair<string, string>[openWith.Count];
      openWith.CopyTo(copy, 0);

      // List the contents of the array.
      //
      outputBlock.Text += "\n";
      foreach (KeyValuePair<string, string> element in copy)
      {
         outputBlock.Text += String.Format("{0}, {1}", element.Key, element.Value) + "\n";
      }
   }
}

/* This code example produces the following output:

txt, notepad.exe
bmp, paint.exe
dib, paint.exe
rtf, wordpad.exe

Contains(KeyValuePair("txt", "notepad.exe")): True

Remove(new KeyValuePair("dib", "paint.exe"))

txt, notepad.exe
bmp, paint.exe
rtf, wordpad.exe

txt, notepad.exe
bmp, paint.exe
rtf, wordpad.exe
 */

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.