NameValueCollection Class

Reference

Definition

Namespace:: System.Collections.Specialized

Assemblies:: System.dll, System.Collections.Specialized.dll

Assembly:: System.Collections.Specialized.dll

Assembly:: System.dll

Assembly:: netstandard.dll

Source:: NameValueCollection.cs

Source:: NameValueCollection.cs

Source:: NameValueCollection.cs

Important

Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.

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

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.

Caution

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

Constructors

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.
NameValueCollection(IEqualityComparer)	Initializes a new instance of the NameValueCollection class that is empty, has the default initial capacity, and uses the specified IEqualityComparer object.
NameValueCollection(IHashCodeProvider, IComparer)	Obsolete. 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.
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.
NameValueCollection(Int32, IHashCodeProvider, IComparer)	Obsolete. 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.
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.
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.
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.
NameValueCollection(SerializationInfo, StreamingContext)	Obsolete. Initializes a new instance of the NameValueCollection class that is serializable and uses the specified SerializationInfo and StreamingContext.

Properties

AllKeys	Gets all the keys in the NameValueCollection.
Count	Gets the number of key/value pairs contained in the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase)
IsReadOnly	Gets or sets a value indicating whether the NameObjectCollectionBase instance is read-only. (Inherited from NameObjectCollectionBase)
Item[Int32]	Gets the entry at the specified index of the NameValueCollection.
Item[String]	Gets or sets the entry with the specified key in the NameValueCollection.
Keys	Gets a NameObjectCollectionBase.KeysCollection instance that contains all the keys in the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase)

Methods

Add(NameValueCollection)	Copies the entries in the specified NameValueCollection to the current NameValueCollection.
Add(String, String)	Adds an entry with the specified name and value to the NameValueCollection.
BaseAdd(String, Object)	Adds an entry with the specified key and value into the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase)
BaseClear()	Removes all entries from the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase)
BaseGet(Int32)	Gets the value of the entry at the specified index of the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase)
BaseGet(String)	Gets the value of the first entry with the specified key from the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase)
BaseGetAllKeys()	Returns a String array that contains all the keys in the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase)
BaseGetAllValues()	Returns an Object array that contains all the values in the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase)
BaseGetAllValues(Type)	Returns an array of the specified type that contains all the values in the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase)
BaseGetKey(Int32)	Gets the key of the entry at the specified index of the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase)
BaseHasKeys()	Gets a value indicating whether the NameObjectCollectionBase instance contains entries whose keys are not `null`. (Inherited from NameObjectCollectionBase)
BaseRemove(String)	Removes the entries with the specified key from the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase)
BaseRemoveAt(Int32)	Removes the entry at the specified index of the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase)
BaseSet(Int32, Object)	Sets the value of the entry at the specified index of the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase)
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)
Clear()	Invalidates the cached arrays and removes all entries from the NameValueCollection.
CopyTo(Array, Int32)	Copies the entire NameValueCollection to a compatible one-dimensional Array, starting at the specified index of the target array.
Equals(Object)	Determines whether the specified object is equal to the current object. (Inherited from Object)
Get(Int32)	Gets the values at the specified index of the NameValueCollection combined into one comma-separated list.
Get(String)	Gets the values associated with the specified key from the NameValueCollection combined into one comma-separated list.
GetEnumerator()	Returns an enumerator that iterates through the NameObjectCollectionBase. (Inherited from NameObjectCollectionBase)
GetHashCode()	Serves as the default hash function. (Inherited from Object)
GetKey(Int32)	Gets the key at the specified index of the NameValueCollection.
GetObjectData(SerializationInfo, StreamingContext)	Obsolete. Implements the ISerializable interface and returns the data needed to serialize the NameObjectCollectionBase instance. (Inherited from NameObjectCollectionBase)
GetType()	Gets the Type of the current instance. (Inherited from Object)
GetValues(Int32)	Gets the values at the specified index of the NameValueCollection.
GetValues(String)	Gets the values associated with the specified key from the NameValueCollection.
HasKeys()	Gets a value indicating whether the NameValueCollection contains keys that are not `null`.
InvalidateCachedArrays()	Resets the cached arrays of the collection to `null`.
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
OnDeserialization(Object)	Implements the ISerializable interface and raises the deserialization event when the deserialization is complete. (Inherited from NameObjectCollectionBase)
Remove(String)	Removes the entries with the specified key from the NameObjectCollectionBase instance.
Set(String, String)	Sets the value of an entry in the NameValueCollection.
ToString()	Returns a string that represents the current object. (Inherited from Object)

Explicit Interface Implementations

ICollection.CopyTo(Array, Int32)	Copies the entire NameObjectCollectionBase to a compatible one-dimensional Array, starting at the specified index of the target array. (Inherited from NameObjectCollectionBase)
ICollection.IsSynchronized	Gets a value indicating whether access to the NameObjectCollectionBase object is synchronized (thread safe). (Inherited from NameObjectCollectionBase)
ICollection.SyncRoot	Gets an object that can be used to synchronize access to the NameObjectCollectionBase object. (Inherited from NameObjectCollectionBase)

Extension Methods

Cast<TResult>(IEnumerable)	Casts the elements of an IEnumerable to the specified type.
OfType<TResult>(IEnumerable)	Filters the elements of an IEnumerable based on a specified type.
AsParallel(IEnumerable)	Enables parallelization of a query.
AsQueryable(IEnumerable)	Converts an IEnumerable to an IQueryable.

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.

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