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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)

'Declaration
<SerializableAttribute> _
Public Class NameValueCollection _
	Inherits NameObjectCollectionBase

The NameValueCollection type exposes the following members.

  NameDescription
Public methodSupported by the XNA FrameworkNameValueCollectionInitializes 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 methodBaseGetAllValuesReturns 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 Nothing. (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 Nothing.
Protected methodSupported by the XNA FrameworkInvalidateCachedArraysResets the cached arrays of the collection to Nothing.
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.

Nothing is allowed as a key or as a value.

Caution noteCaution

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.

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


' 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)
        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
'
'


.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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