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NameValueCollection Class

Represents a collection of associated String keys and String values that can be accessed either with the key or with the index.

Namespace:  System.Collections.Specialized
Assembly:  System (in System.dll)
[SerializableAttribute]
public class NameValueCollection : NameObjectCollectionBase

The NameValueCollection type exposes the following members.

  Name Description
Public method Supported by the XNA Framework NameValueCollection Initializes a new instance of the NameValueCollection class that is empty, has the default initial capacity and uses the default case-insensitive hash code provider and the default case-insensitive comparer.
Public method Supported by the XNA Framework NameValueCollection(IEqualityComparer) Initializes a new instance of the NameValueCollection class that is empty, has the default initial capacity, and uses the specified IEqualityComparer object.
Public method Supported by the XNA Framework NameValueCollection(Int32) Initializes a new instance of the NameValueCollection class that is empty, has the specified initial capacity and uses the default case-insensitive hash code provider and the default case-insensitive comparer.
Public method Supported by the XNA Framework NameValueCollection(NameValueCollection) Copies the entries from the specified NameValueCollection to a new NameValueCollection with the same initial capacity as the number of entries copied and using the same hash code provider and the same comparer as the source collection.
Public method Supported by the XNA Framework NameValueCollection(IHashCodeProvider, IComparer) Obsolete. Initializes a new instance of the NameValueCollection class that is empty, has the default initial capacity and uses the specified hash code provider and the specified comparer.
Public method Supported by the XNA Framework NameValueCollection(Int32, IEqualityComparer) Initializes a new instance of the NameValueCollection class that is empty, has the specified initial capacity, and uses the specified IEqualityComparer object.
Public method Supported by the XNA Framework NameValueCollection(Int32, NameValueCollection) Copies the entries from the specified NameValueCollection to a new NameValueCollection with the specified initial capacity or the same initial capacity as the number of entries copied, whichever is greater, and using the default case-insensitive hash code provider and the default case-insensitive comparer.
Protected method NameValueCollection(SerializationInfo, StreamingContext) Initializes a new instance of the NameValueCollection class that is serializable and uses the specified System.Runtime.Serialization.SerializationInfo and System.Runtime.Serialization.StreamingContext.
Public method Supported by the XNA Framework NameValueCollection(Int32, IHashCodeProvider, IComparer) Obsolete. Initializes a new instance of the NameValueCollection class that is empty, has the specified initial capacity and uses the specified hash code provider and the specified comparer.
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  Name Description
Public property Supported by the XNA Framework AllKeys Gets all the keys in the NameValueCollection.
Public property Supported by the XNA Framework Count Gets the number of key/value pairs contained in the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase.)
Protected property Supported by the XNA Framework IsReadOnly Gets or sets a value indicating whether the NameObjectCollectionBase instance is read-only. (Inherited from NameObjectCollectionBase.)
Public property Supported by the XNA Framework Item(Int32) Gets the entry at the specified index of the NameValueCollection.
Public property Supported by the XNA Framework Item(String) Gets or sets the entry with the specified key in the NameValueCollection.
Public property Supported by the XNA Framework Keys Gets a NameObjectCollectionBase.KeysCollection instance that contains all the keys in the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase.)
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  Name Description
Public method Supported by the XNA Framework Add(NameValueCollection) Copies the entries in the specified NameValueCollection to the current NameValueCollection.
Public method Supported by the XNA Framework Add(String, String) Adds an entry with the specified name and value to the NameValueCollection.
Protected method Supported by the XNA Framework BaseAdd Adds an entry with the specified key and value into the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase.)
Protected method Supported by the XNA Framework BaseClear Removes all entries from the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase.)
Protected method Supported by the XNA Framework BaseGet(Int32) Gets the value of the entry at the specified index of the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase.)
Protected method Supported by the XNA Framework BaseGet(String) Gets the value of the first entry with the specified key from the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase.)
Protected method Supported by the XNA Framework BaseGetAllKeys Returns a String array that contains all the keys in the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase.)
Protected method BaseGetAllValues Returns an Object array that contains all the values in the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase.)
Protected method BaseGetAllValues(Type) Returns an array of the specified type that contains all the values in the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase.)
Protected method Supported by the XNA Framework BaseGetKey Gets the key of the entry at the specified index of the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase.)
Protected method Supported by the XNA Framework BaseHasKeys Gets a value indicating whether the NameObjectCollectionBase instance contains entries whose keys are not Nothing. (Inherited from NameObjectCollectionBase.)
Protected method Supported by the XNA Framework BaseRemove Removes the entries with the specified key from the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase.)
Protected method Supported by the XNA Framework BaseRemoveAt Removes the entry at the specified index of the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase.)
Protected method Supported by the XNA Framework BaseSet(Int32, Object) Sets the value of the entry at the specified index of the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase.)
Protected method Supported by the XNA Framework BaseSet(String, Object) Sets the value of the first entry with the specified key in the NameObjectCollectionBase instance, if found; otherwise, adds an entry with the specified key and value into the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase.)
Public method Supported by the XNA Framework Clear Invalidates the cached arrays and removes all entries from the NameValueCollection.
Public method CopyTo Copies the entire NameValueCollection to a compatible one-dimensional Array, starting at the specified index of the target array.
Public method Supported by the XNA Framework Equals(Object) Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
Protected method Supported by the XNA Framework Finalize Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public method Supported by the XNA Framework Get(Int32) Gets the values at the specified index of the NameValueCollection combined into one comma-separated list.
Public method Supported by the XNA Framework Get(String) Gets the values associated with the specified key from the NameValueCollection combined into one comma-separated list.
Public method Supported by the XNA Framework GetEnumerator Returns an enumerator that iterates through the NameObjectCollectionBase. (Inherited from NameObjectCollectionBase.)
Public method Supported by the XNA Framework GetHashCode Serves as a hash function for a particular type. (Inherited from Object.)
Public method Supported by the XNA Framework GetKey Gets the key at the specified index of the NameValueCollection.
Public method GetObjectData Implements the ISerializable interface and returns the data needed to serialize the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase.)
Public method Supported by the XNA Framework GetType Gets the Type of the current instance. (Inherited from Object.)
Public method Supported by the XNA Framework GetValues(Int32) Gets the values at the specified index of the NameValueCollection.
Public method Supported by the XNA Framework GetValues(String) Gets the values associated with the specified key from the NameValueCollection.
Public method Supported by the XNA Framework HasKeys Gets a value indicating whether the NameValueCollection contains keys that are not Nothing.
Protected method Supported by the XNA Framework InvalidateCachedArrays Resets the cached arrays of the collection to Nothing.
Protected method Supported by the XNA Framework MemberwiseClone Creates a shallow copy of the current Object. (Inherited from Object.)
Public method OnDeserialization Implements the ISerializable interface and raises the deserialization event when the deserialization is complete. (Inherited from NameObjectCollectionBase.)
Public method Supported by the XNA Framework Remove Removes the entries with the specified key from the NameObjectCollectionBase instance.
Public method Supported by the XNA Framework Set Sets the value of an entry in the NameValueCollection.
Public method Supported by the XNA Framework ToString Returns a string that represents the current object. (Inherited from Object.)
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  Name Description
Explicit interface implemetation Private method Supported by the XNA Framework ICollection.CopyTo Copies the entire NameObjectCollectionBase to a compatible one-dimensional Array, starting at the specified index of the target array. (Inherited from NameObjectCollectionBase.)
Explicit interface implemetation Private property Supported by the XNA Framework ICollection.IsSynchronized Gets a value indicating whether access to the NameObjectCollectionBase object is synchronized (thread safe). (Inherited from NameObjectCollectionBase.)
Explicit interface implemetation Private property Supported by the XNA Framework ICollection.SyncRoot Gets an object that can be used to synchronize access to the NameObjectCollectionBase object. (Inherited from NameObjectCollectionBase.)
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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.

Collections of this type do not preserve the ordering of element, 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 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.

Nothing is allowed as a key or as a value.

Caution note Caution

The Get method does not distinguish between Nothing which is returned because the specified key is not found and Nothing which is returned because the value associated with the key is Nothing.

Topic Location
How to: Read Application Settings from the Web.config File Configuring ASP .NET Web Applications
How to: Read Application Settings from the Web.config File Configuring ASP .NET Web Applications

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


*/


.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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.

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