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11/18/2011

KeyValuePair<TKey, TValue> Structure

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

Defines a key/value pair that can be set or retrieved.

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

Syntax

'Declaration
Public Structure KeyValuePair(Of TKey, TValue)

public struct KeyValuePair<TKey, TValue>

Type Parameters

TKey
The type of the key.

TValue
The type of the value.

The KeyValuePair<TKey, TValue> type exposes the following members.

Constructors

	Name	Description
	KeyValuePair<TKey, TValue>	Initializes a new instance of the KeyValuePair<TKey, TValue> structure with the specified key and value.

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Properties

	Name	Description
	Key	Gets the key in the key/value pair.
	Value	Gets the value in the key/value pair.

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Methods

	Name	Description
	Equals	Indicates whether this instance and a specified object are equal. (Inherited from ValueType.)
	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.)
	GetHashCode	Returns the hash code for this instance. (Inherited from ValueType.)
	GetType	Gets the Type of the current instance. (Inherited from Object.)
	MemberwiseClone	Creates a shallow copy of the current Object. (Inherited from Object.)
	ToString	Returns a string representation of the KeyValuePair<TKey, TValue>, using the string representations of the key and value. (Overrides ValueType.ToString().)

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Remarks

The Dictionary<TKey, TValue>.Enumerator.Current property returns an instance of this type.

The foreach statement of the C# language (for each in C++, For Each in Visual Basic) requires the type of the elements in the collection. Since each element of a collection based on IDictionary<TKey, TValue> is a key/value pair, the element type is not the type of the key or the type of the value. Instead, the element type is KeyValuePair<TKey, TValue>. For example:

foreach (KeyValuePair<int, string> kvp in myDictionary) {...}

for each (KeyValuePair<int, String^> kvp in myDictionary) {...}

For Each kvp As KeyValuePair(Of Integer, String) In myDictionary
    ...
Next kvp

The foreach statement is a wrapper around the enumerator, which allows only reading from, not writing to, the collection.

Examples

The following code example shows how to enumerate the keys and values in a dictionary, using the KeyValuePair<TKey, TValue> structure.

This code is part of a larger example (the second example) provided for the Dictionary<TKey, TValue> class.

' When you use foreach to enumerate dictionary elements,
' the elements are retrieved as KeyValuePair objects.
outputBlock.Text &= vbCrLf
For Each kvp As KeyValuePair(Of String, String) In openWith
   outputBlock.Text &= String.Format("Key = {0}, Value = {1}", _
       kvp.Key, kvp.Value) & vbCrLf
Next kvp

// When you use foreach to enumerate dictionary elements,
// the elements are retrieved as KeyValuePair objects.
outputBlock.Text += "\n";
foreach (KeyValuePair<string, string> kvp in openWith)
{
   outputBlock.Text += String.Format("Key = {0}, Value = {1}",
       kvp.Key, kvp.Value) + "\n";
}

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

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

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