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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 ref class NameValueCollection : public NameObjectCollectionBase

The NameValueCollection type exposes the following members.

  NameDescription
Public methodSupported by the XNA FrameworkNameValueCollection()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 methodSupported by the XNA FrameworkNameValueCollection(IEqualityComparer)Initializes a new instance of the NameValueCollection class that is empty, has the default initial capacity, and uses the specified IEqualityComparer object.
Public methodSupported by the XNA FrameworkNameValueCollection(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 methodSupported by the XNA FrameworkNameValueCollection(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 methodSupported by the XNA FrameworkNameValueCollection(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 methodSupported by the XNA FrameworkNameValueCollection(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 methodSupported by the XNA FrameworkNameValueCollection(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 methodNameValueCollection(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 methodSupported by the XNA FrameworkNameValueCollection(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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  NameDescription
Public propertySupported by the XNA FrameworkAllKeysGets all the keys in the NameValueCollection.
Public propertySupported by the XNA FrameworkCountGets the number of key/value pairs contained in the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase.)
Protected propertySupported by the XNA FrameworkIsReadOnlyGets or sets a value indicating whether the NameObjectCollectionBase instance is read-only. (Inherited from NameObjectCollectionBase.)
Public propertySupported by the XNA FrameworkItem[Int32]Gets the entry at the specified index of the NameValueCollection.
Public propertySupported by the XNA FrameworkItem[String]Gets or sets the entry with the specified key in the NameValueCollection.
Public propertySupported by the XNA FrameworkKeysGets a NameObjectCollectionBase::KeysCollection instance that contains all the keys in the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase.)
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  NameDescription
Public methodSupported by the XNA FrameworkAdd(NameValueCollection)Copies the entries in the specified NameValueCollection to the current NameValueCollection.
Public methodSupported by the XNA FrameworkAdd(String, String)Adds an entry with the specified name and value to the NameValueCollection.
Protected methodSupported by the XNA FrameworkBaseAddAdds an entry with the specified key and value into the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase.)
Protected methodSupported by the XNA FrameworkBaseClearRemoves all entries from the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase.)
Protected methodSupported by the XNA FrameworkBaseGet(Int32)Gets the value of the entry at the specified index of the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase.)
Protected methodSupported by the XNA FrameworkBaseGet(String)Gets the value of the first entry with the specified key from the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase.)
Protected methodSupported by the XNA FrameworkBaseGetAllKeysReturns a String array that contains all the keys in the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase.)
Protected methodBaseGetAllValues()Returns an Object array that contains all the values in the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase.)
Protected methodBaseGetAllValues(Type)Returns an array of the specified type that contains all the values in the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase.)
Protected methodSupported by the XNA FrameworkBaseGetKeyGets the key of the entry at the specified index of the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase.)
Protected methodSupported by the XNA FrameworkBaseHasKeysGets a value indicating whether the NameObjectCollectionBase instance contains entries whose keys are not nullptr. (Inherited from NameObjectCollectionBase.)
Protected methodSupported by the XNA FrameworkBaseRemoveRemoves the entries with the specified key from the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase.)
Protected methodSupported by the XNA FrameworkBaseRemoveAtRemoves the entry at the specified index of the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase.)
Protected methodSupported by the XNA FrameworkBaseSet(Int32, Object)Sets the value of the entry at the specified index of the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase.)
Protected methodSupported by the XNA FrameworkBaseSet(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 methodSupported by the XNA FrameworkClearInvalidates the cached arrays and removes all entries from the NameValueCollection.
Public methodCopyToCopies the entire NameValueCollection to a compatible one-dimensional Array, starting at the specified index of the target array.
Public methodSupported by the XNA FrameworkEquals(Object)Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
Protected methodSupported by the XNA FrameworkFinalizeAllows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public methodSupported by the XNA FrameworkGet(Int32)Gets the values at the specified index of the NameValueCollection combined into one comma-separated list.
Public methodSupported by the XNA FrameworkGet(String)Gets the values associated with the specified key from the NameValueCollection combined into one comma-separated list.
Public methodSupported by the XNA FrameworkGetEnumeratorReturns an enumerator that iterates through the NameObjectCollectionBase. (Inherited from NameObjectCollectionBase.)
Public methodSupported by the XNA FrameworkGetHashCodeServes as a hash function for a particular type. (Inherited from Object.)
Public methodSupported by the XNA FrameworkGetKeyGets the key at the specified index of the NameValueCollection.
Public methodGetObjectDataImplements the ISerializable interface and returns the data needed to serialize the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase.)
Public methodSupported by the XNA FrameworkGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodSupported by the XNA FrameworkGetValues(Int32)Gets the values at the specified index of the NameValueCollection.
Public methodSupported by the XNA FrameworkGetValues(String)Gets the values associated with the specified key from the NameValueCollection.
Public methodSupported by the XNA FrameworkHasKeysGets a value indicating whether the NameValueCollection contains keys that are not nullptr.
Protected methodSupported by the XNA FrameworkInvalidateCachedArraysResets the cached arrays of the collection to nullptr.
Protected methodSupported by the XNA FrameworkMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodOnDeserializationImplements the ISerializable interface and raises the deserialization event when the deserialization is complete. (Inherited from NameObjectCollectionBase.)
Public methodSupported by the XNA FrameworkRemoveRemoves the entries with the specified key from the NameObjectCollectionBase instance.
Public methodSupported by the XNA FrameworkSetSets the value of an entry in the NameValueCollection.
Public methodSupported by the XNA FrameworkToStringReturns a string that represents the current object. (Inherited from Object.)
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  NameDescription
Explicit interface implemetationPrivate methodSupported by the XNA FrameworkICollection::CopyToCopies the entire NameObjectCollectionBase to a compatible one-dimensional Array, starting at the specified index of the target array. (Inherited from NameObjectCollectionBase.)
Explicit interface implemetationPrivate propertySupported by the XNA FrameworkICollection::IsSynchronizedGets a value indicating whether access to the NameObjectCollectionBase object is synchronized (thread safe). (Inherited from NameObjectCollectionBase.)
Explicit interface implemetationPrivate propertySupported by the XNA FrameworkICollection::SyncRootGets 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.

nullptr is allowed as a key or as a value.

Caution noteCaution

The Get method does not distinguish between nullptr which is returned because the specified key is not found and nullptr which is returned because the value associated with the key is nullptr.

TopicLocation
How to: Read Application Settings from the Web.config FileConfiguring ASP .NET Web Applications
How to: Read Application Settings from the Web.config FileConfiguring ASP .NET Web Applications


#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


*/


.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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