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

 

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

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

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.

This method determines equality using the default equality comparer Default for the KeyValuePair(Of TKey, TValue) structure.

This method approaches an O(1) operation.

The following example shows how to use the ICollection(Of KeyValuePair(Of TKey, TValue)).Add, ICollection(Of KeyValuePair(Of TKey, TValue)).Contains, ICollection(Of KeyValuePair(Of TKey, TValue)).CopyTo, and ICollection(Of KeyValuePair(Of TKey, TValue)).Remove methods of the ICollection(Of T) generic interface to manipulate a Dictionary(Of TKey, TValue) object.

Imports System
Imports System.Collections.Generic

Public Class Example

    Public Shared Sub Main() 

        ' 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"))

        Console.WriteLine()
        For Each element As KeyValuePair(Of String, String) in openWith
            Console.WriteLine("{0}, {1}", element.Key, element.Value)
        Next

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

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

        Console.WriteLine()
        For Each element As KeyValuePair(Of String, String) in openWith
            Console.WriteLine("{0}, {1}", element.Key, element.Value)
        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.
        '
        Console.WriteLine()
        For Each element As KeyValuePair(Of String, String) in copy
            Console.WriteLine("{0}, {1}", element.Key, element.Value)
        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 

Universal Windows Platform
Available since 8
.NET Framework
Available since 2.0
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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