NameValueCollection Class

Definition

public ref class NameValueCollection : System::Collections::Specialized::NameObjectCollectionBase

public class NameValueCollection : System.Collections.Specialized.NameObjectCollectionBase

[System.Serializable]
public class NameValueCollection : System.Collections.Specialized.NameObjectCollectionBase

type NameValueCollection = class
    inherit NameObjectCollectionBase

[<System.Serializable>]
type NameValueCollection = class
    inherit NameObjectCollectionBase

Public Class NameValueCollection
Inherits NameObjectCollectionBase

Inheritance

Object

NameObjectCollectionBase

NameValueCollection

Derived

System.Net.WebHeaderCollection

System.Web.HttpClientCertificate

Attributes

SerializableAttribute

Examples

#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


*/

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 )  {
      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


*/

' The following code example demonstrates several of the properties and methods of ListDictionary.

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

    Public Shared Sub PrintKeysAndValues(myCol As NameValueCollection)
        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

    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

End Class


'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
'
'

Remarks

This collection is based on the NameObjectCollectionBase class. Each element of the collection is a key/value pair. However, unlike the NameObjectCollectionBase, this class can store multiple string values under a single key.

This class can be used for headers, query strings and form data.

Collections of this type do not preserve the ordering of elements, and no particular ordering is guaranteed when enumerating the collection.

The capacity of a NameValueCollection is the number of elements the NameValueCollection can hold. As elements are added, its 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 a CaseInsensitiveComparer that uses the conventions of the invariant culture; that is, key comparisons are case-insensitive by default. To perform case-sensitive key comparisons, call the NameValueCollection.NameValueCollection(IEqualityComparer) constructor, and provide a value of StringComparer.CurrentCulture, StringComparer.InvariantCulture, or StringComparer.Ordinal as the equalityComparer argument. For more information about how culture affects comparisons and sorting, see Performing Culture-Insensitive String Operations.

null is allowed as a key or as a value.

Constructors

Properties

Methods

Explicit Interface Implementations

Extension Methods

Applies to

Thread Safety

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.

See also

• NameObjectCollectionBase
• Performing Culture-Insensitive String Operations