ICollection(KeyValuePair(TKey, TValue)).Contains Method

Dictionary(Of TKey, TValue).ICollection(Of KeyValuePair(Of TKey, TValue)).Contains Method

[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]

Determines whether the ICollection(Of T) contains a specific key and value.

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

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

Parameters

keyValuePair
Type: System.Collections.Generic.KeyValuePair(Of TKey, TValue)
The KeyValuePair(Of TKey, TValue) structure to locate in the ICollection(Of T).

Return Value

Type: System.Boolean
true if keyValuePair is found in the ICollection(Of T); otherwise, false.

Implements

ICollection(Of T).Contains(T)

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

This method approaches an O(1) operation.

The following example shows how to use explicit interface implementations of the System.Collections.Generic.ICollection(Of T) generic interface to manipulate a Dictionary(Of 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 


Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Windows Phone

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