Represents a collection of associated String keys and String values that can be accessed either with the key or with the index.
(in System.dll)
Visual Basic (Declaration)
<SerializableAttribute> _
Public Class NameValueCollection _
Inherits NameObjectCollectionBase
Dim instance As NameValueCollection
[SerializableAttribute]
public class NameValueCollection : NameObjectCollectionBase
[SerializableAttribute]
public ref class NameValueCollection : public NameObjectCollectionBase
public class NameValueCollection extends NameObjectCollectionBase
This collection is based on the NameObjectCollectionBase class. However, unlike the NameObjectCollectionBase, this class stores multiple string values under a single key.
This class can be used for headers, query strings and form data.
Each element is a key/value pair.
The capacity of a NameValueCollection is the number of elements the NameValueCollection can hold. As elements are added to a NameValueCollection, the capacity is automatically increased as required through reallocation.
The hash code provider dispenses hash codes for keys in the NameValueCollection. The default hash code provider is the CaseInsensitiveHashCodeProvider.
The comparer determines whether two keys are equal. The default comparer is the CaseInsensitiveComparer.
In .NET Framework version 1.0, this class uses culture-sensitive string comparisons. However, in .NET Framework version 1.1 and later, this class uses CultureInfo..::.InvariantCulture when comparing strings. For more information about how culture affects comparisons and sorting, see Comparing and Sorting Data for a Specific Culture Comparing and Sorting Data for a Specific Cultureand Performing Culture-Insensitive String Operations.
nullNothingnullptra null reference (Nothing in Visual Basic) is allowed as a key or as a value.
.gif) Caution: |
|---|
The Get method does not distinguish between nullNothingnullptra null reference (Nothing in Visual Basic) which is returned because the specified key is not found and nullNothingnullptra null reference (Nothing in Visual Basic) which is returned because the value associated with the key is nullNothingnullptra null reference (Nothing in Visual Basic). |
' The following code example demonstrates several of the properties and methods of ListDictionary.
Imports System
Imports System.Collections
Imports System.Collections.Specialized
Public Class SamplesNameValueCollection
Public Shared Sub Main()
' Creates and initializes a new NameValueCollection.
Dim myCol As New NameValueCollection()
myCol.Add("red", "rojo")
myCol.Add("green", "verde")
myCol.Add("blue", "azul")
myCol.Add("red", "rouge")
' Displays the values in the NameValueCollection in two different ways.
Console.WriteLine("Displays the elements using the AllKeys property and the Item (indexer) property:")
PrintKeysAndValues(myCol)
Console.WriteLine("Displays the elements using GetKey and Get:")
PrintKeysAndValues2(myCol)
' Gets a value either by index or by key.
Console.WriteLine("Index 1 contains the value {0}.", myCol(1))
Console.WriteLine("Key ""red"" has the value {0}.", myCol("red"))
Console.WriteLine()
' Copies the values to a string array and displays the string array.
Dim myStrArr(myCol.Count) As String
myCol.CopyTo(myStrArr, 0)
Console.WriteLine("The string array contains:")
Dim s As String
For Each s In myStrArr
Console.WriteLine(" {0}", s)
Next s
Console.WriteLine()
' Searches for a key and deletes it.
myCol.Remove("green")
Console.WriteLine("The collection contains the following elements after removing ""green"":")
PrintKeysAndValues(myCol)
' Clears the entire collection.
myCol.Clear()
Console.WriteLine("The collection contains the following elements after it is cleared:")
PrintKeysAndValues(myCol)
End Sub 'Main
Public Shared Sub PrintKeysAndValues(myCol As NameValueCollection)
Dim myEnumerator As IEnumerator = myCol.GetEnumerator()
Console.WriteLine(" KEY VALUE")
Dim s As String
For Each s In myCol.AllKeys
Console.WriteLine(" {0,-10} {1}", s, myCol(s))
Next s
Console.WriteLine()
End Sub 'PrintKeysAndValues
Public Shared Sub PrintKeysAndValues2(myCol As NameValueCollection)
Console.WriteLine(" [INDEX] KEY VALUE")
Dim i As Integer
For i = 0 To myCol.Count - 1
Console.WriteLine(" [{0}] {1,-10} {2}", i, myCol.GetKey(i), myCol.Get(i))
Next i
Console.WriteLine()
End Sub 'PrintKeysAndValues2
End Class 'SamplesNameValueCollection
'This code produces the following output.
'
'Displays the elements using the AllKeys property and the Item (indexer) property:
' KEY VALUE
' red rojo,rouge
' green verde
' blue azul
'
'Displays the elements using GetKey and Get:
' [INDEX] KEY VALUE
' [0] red rojo,rouge
' [1] green verde
' [2] blue azul
'
'Index 1 contains the value verde.
'Key "red" has the value rojo,rouge.
'
'The string array contains:
' red
' green
' blue
'
'
'The collection contains the following elements after removing "green":
' KEY VALUE
' red rojo,rouge
' blue azul
'
'The collection contains the following elements after it is cleared:
' KEY VALUE
'
'
using System;
using System.Collections;
using System.Collections.Specialized;
public class SamplesNameValueCollection {
public static void Main() {
// Creates and initializes a new NameValueCollection.
NameValueCollection myCol = new NameValueCollection();
myCol.Add( "red", "rojo" );
myCol.Add( "green", "verde" );
myCol.Add( "blue", "azul" );
myCol.Add( "red", "rouge" );
// Displays the values in the NameValueCollection in two different ways.
Console.WriteLine( "Displays the elements using the AllKeys property and the Item (indexer) property:" );
PrintKeysAndValues( myCol );
Console.WriteLine( "Displays the elements using GetKey and Get:" );
PrintKeysAndValues2( myCol );
// Gets a value either by index or by key.
Console.WriteLine( "Index 1 contains the value {0}.", myCol[1] );
Console.WriteLine( "Key \"red\" has the value {0}.", myCol["red"] );
Console.WriteLine();
// Copies the values to a string array and displays the string array.
String[] myStrArr = new String[myCol.Count];
myCol.CopyTo( myStrArr, 0 );
Console.WriteLine( "The string array contains:" );
foreach ( String s in myStrArr )
Console.WriteLine( " {0}", s );
Console.WriteLine();
// Searches for a key and deletes it.
myCol.Remove( "green" );
Console.WriteLine( "The collection contains the following elements after removing \"green\":" );
PrintKeysAndValues( myCol );
// Clears the entire collection.
myCol.Clear();
Console.WriteLine( "The collection contains the following elements after it is cleared:" );
PrintKeysAndValues( myCol );
}
public static void PrintKeysAndValues( NameValueCollection myCol ) {
IEnumerator myEnumerator = myCol.GetEnumerator();
Console.WriteLine( " KEY VALUE" );
foreach ( String s in myCol.AllKeys )
Console.WriteLine( " {0,-10} {1}", s, myCol[s] );
Console.WriteLine();
}
public static void PrintKeysAndValues2( NameValueCollection myCol ) {
Console.WriteLine( " [INDEX] KEY VALUE" );
for ( int i = 0; i < myCol.Count; i++ )
Console.WriteLine( " [{0}] {1,-10} {2}", i, myCol.GetKey(i), myCol.Get(i) );
Console.WriteLine();
}
}
/*
This code produces the following output.
Displays the elements using the AllKeys property and the Item (indexer) property:
KEY VALUE
red rojo,rouge
green verde
blue azul
Displays the elements using GetKey and Get:
[INDEX] KEY VALUE
[0] red rojo,rouge
[1] green verde
[2] blue azul
Index 1 contains the value verde.
Key "red" has the value rojo,rouge.
The string array contains:
rojo,rouge
verde
azul
The collection contains the following elements after removing "green":
KEY VALUE
red rojo,rouge
blue azul
The collection contains the following elements after it is cleared:
KEY VALUE
*/
#using <System.dll>
using namespace System;
using namespace System::Collections;
using namespace System::Collections::Specialized;
void PrintKeysAndValues( NameValueCollection^ myCol );
void PrintKeysAndValues2( NameValueCollection^ myCol );
int main()
{
// Creates and initializes a new NameValueCollection.
NameValueCollection^ myCol = gcnew NameValueCollection;
myCol->Add( "red", "rojo" );
myCol->Add( "green", "verde" );
myCol->Add( "blue", "azul" );
myCol->Add( "red", "rouge" );
// Displays the values in the NameValueCollection in two different ways.
Console::WriteLine( "Displays the elements using the AllKeys property and the Item (indexer) property:" );
PrintKeysAndValues( myCol );
Console::WriteLine( "Displays the elements using GetKey and Get:" );
PrintKeysAndValues2( myCol );
// Gets a value either by index or by key.
Console::WriteLine( "Index 1 contains the value {0}.", myCol[ 1 ] );
Console::WriteLine( "Key \"red\" has the value {0}.", myCol[ "red" ] );
Console::WriteLine();
// Copies the values to a string array and displays the string array.
array<String^>^myStrArr = gcnew array<String^>(myCol->Count);
myCol->CopyTo( myStrArr, 0 );
Console::WriteLine( "The string array contains:" );
for each ( String^ s in myStrArr )
Console::WriteLine( " {0}", s );
Console::WriteLine();
// Searches for a key and deletes it.
myCol->Remove( "green" );
Console::WriteLine( "The collection contains the following elements after removing \"green\":" );
PrintKeysAndValues( myCol );
// Clears the entire collection.
myCol->Clear();
Console::WriteLine( "The collection contains the following elements after it is cleared:" );
PrintKeysAndValues( myCol );
}
void PrintKeysAndValues( NameValueCollection^ myCol )
{
Console::WriteLine( " KEY VALUE" );
for each ( String^ s in myCol->AllKeys )
Console::WriteLine( " {0,-10} {1}", s, myCol[s] );
Console::WriteLine();
}
void PrintKeysAndValues2( NameValueCollection^ myCol )
{
Console::WriteLine( " [INDEX] KEY VALUE" );
for ( int i = 0; i < myCol->Count; i++ )
Console::WriteLine( " [{0}] {1,-10} {2}", i, myCol->GetKey( i ), myCol->Get( i ) );
Console::WriteLine();
}
/*
This code produces the following output.
Displays the elements using the AllKeys property and the Item (indexer) property:
KEY VALUE
red rojo,rouge
green verde
blue azul
Displays the elements using GetKey and Get:
[INDEX] KEY VALUE
[0] red rojo,rouge
[1] green verde
[2] blue azul
Index 1 contains the value verde.
Key "red" has the value rojo,rouge.
The string array contains:
rojo,rouge
verde
azul
The collection contains the following elements after removing "green":
KEY VALUE
red rojo,rouge
blue azul
The collection contains the following elements after it is cleared:
KEY VALUE
*/
System..::.Object
System.Collections.Specialized..::.NameObjectCollectionBase
System.Collections.Specialized..::.NameValueCollection
System.Net..::.WebHeaderCollection
System.Web..::.HttpClientCertificate
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 NameValueCollection, but derived classes can create their own synchronized versions of the NameValueCollection using the SyncRoot property of the NameObjectCollectionBase class.
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.
Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
.NET Framework
Supported in: 3.5, 3.0, 2.0, 1.1, 1.0
.NET Compact Framework
Supported in: 3.5, 2.0, 1.0
XNA Framework
Supported in: 3.0, 2.0, 1.0
Reference
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