NameValueCollection Class
Definition
Important
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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
- Derived
- Attributes
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) |
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(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(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 |
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 |
InvalidateCachedArrays() |
Resets the cached arrays of the collection to |
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.