StringDictionary Class

Definition

public ref class StringDictionary : System::Collections::IEnumerable

public class StringDictionary : System.Collections.IEnumerable

[System.Serializable]
public class StringDictionary : System.Collections.IEnumerable

type StringDictionary = class
 interface IEnumerable

[<System.Serializable>]
type StringDictionary = class
 interface IEnumerable

Public Class StringDictionary
Implements IEnumerable

Inheritance

Object

StringDictionary

Attributes

SerializableAttribute

Implements

IEnumerable

Examples

The following code example demonstrates several of the properties and methods of StringDictionary.

using System;
using System.Collections;
using System.Collections.Specialized;

public class SamplesStringDictionary {

 public static void Main() {

 // Creates and initializes a new StringDictionary.
 StringDictionary myCol = new StringDictionary();
 myCol.Add( "red", "rojo" );
 myCol.Add( "green", "verde" );
 myCol.Add( "blue", "azul" );

 // Display the contents of the collection using foreach. This is the preferred method.
 Console.WriteLine( "Displays the elements using foreach:" );
 PrintKeysAndValues1( myCol );

 // Display the contents of the collection using the enumerator.
 Console.WriteLine( "Displays the elements using the IEnumerator:" );
 PrintKeysAndValues2( myCol );

 // Display the contents of the collection using the Keys, Values, Count, and Item properties.
 Console.WriteLine( "Displays the elements using the Keys, Values, Count, and Item properties:" );
 PrintKeysAndValues3( myCol );

 // Copies the StringDictionary to an array with DictionaryEntry elements.
 DictionaryEntry[] myArr = new DictionaryEntry[myCol.Count];
 myCol.CopyTo( myArr, 0 );

 // Displays the values in the array.
 Console.WriteLine( "Displays the elements in the array:" );
 Console.WriteLine( " KEY VALUE" );
 for ( int i = 0; i < myArr.Length; i++ )
 Console.WriteLine( " {0,-10} {1}", myArr[i].Key, myArr[i].Value );
 Console.WriteLine();

 // Searches for a value.
 if ( myCol.ContainsValue( "amarillo" ) )
 Console.WriteLine( "The collection contains the value \"amarillo\"." );
 else
 Console.WriteLine( "The collection does not contain the value \"amarillo\"." );
 Console.WriteLine();

 // Searches for a key and deletes it.
 if ( myCol.ContainsKey( "green" ) )
 myCol.Remove( "green" );
 Console.WriteLine( "The collection contains the following elements after removing \"green\":" );
 PrintKeysAndValues1( myCol );

 // Clears the entire collection.
 myCol.Clear();
 Console.WriteLine( "The collection contains the following elements after it is cleared:" );
 PrintKeysAndValues1( myCol );
 }

 // Uses the foreach statement which hides the complexity of the enumerator.
 // NOTE: The foreach statement is the preferred way of enumerating the contents of a collection.
 public static void PrintKeysAndValues1( StringDictionary myCol ) {
 Console.WriteLine( " KEY VALUE" );
 foreach ( DictionaryEntry de in myCol )
 Console.WriteLine( " {0,-25} {1}", de.Key, de.Value );
 Console.WriteLine();
 }

 // Uses the enumerator.
 // NOTE: The foreach statement is the preferred way of enumerating the contents of a collection.
 public static void PrintKeysAndValues2( StringDictionary myCol ) {
 IEnumerator myEnumerator = myCol.GetEnumerator();
 DictionaryEntry de;
 Console.WriteLine( " KEY VALUE" );
 while ( myEnumerator.MoveNext() ) {
 de = (DictionaryEntry) myEnumerator.Current;
 Console.WriteLine( " {0,-25} {1}", de.Key, de.Value );
 }
 Console.WriteLine();
 }

 // Uses the Keys, Values, Count, and Item properties.
 public static void PrintKeysAndValues3( StringDictionary myCol ) {
 String[] myKeys = new String[myCol.Count];
 myCol.Keys.CopyTo( myKeys, 0 );

 Console.WriteLine( " INDEX KEY VALUE" );
 for ( int i = 0; i < myCol.Count; i++ )
 Console.WriteLine( " {0,-5} {1,-25} {2}", i, myKeys[i], myCol[myKeys[i]] );
 Console.WriteLine();
 }
}

/*
This code produces the following output.

Displays the elements using foreach:
 KEY VALUE
 red rojo
 blue azul
 green verde

Displays the elements using the IEnumerator:
 KEY VALUE
 red rojo
 blue azul
 green verde

Displays the elements using the Keys, Values, Count, and Item properties:
 INDEX KEY VALUE
 0 red rojo
 1 blue azul
 2 green verde

Displays the elements in the array:
 KEY VALUE
 red rojo
 blue azul
 green verde

The collection does not contain the value "amarillo".

The collection contains the following elements after removing "green":
 KEY VALUE
 red rojo
 blue azul

The collection contains the following elements after it is cleared:
 KEY VALUE

*/

Imports System.Collections
Imports System.Collections.Specialized

Public Class SamplesStringDictionary 

 Public Shared Sub Main()

 ' Creates and initializes a new StringDictionary.
 Dim myCol As New StringDictionary()
 myCol.Add("red", "rojo")
 myCol.Add("green", "verde")
 myCol.Add("blue", "azul")

 ' Display the contents of the collection using For Each. This is the preferred method.
 Console.WriteLine("Displays the elements using For Each:")
 PrintKeysAndValues1(myCol)

 ' Display the contents of the collection using the enumerator.
 Console.WriteLine("Displays the elements using the IEnumerator:")
 PrintKeysAndValues2(myCol)

 ' Display the contents of the collection using the Keys, Values, Count, and Item properties.
 Console.WriteLine("Displays the elements using the Keys, Values, Count, and Item properties:")
 PrintKeysAndValues3(myCol)

 ' Copies the StringDictionary to an array with DictionaryEntry elements.
 Dim myArr(myCol.Count) As DictionaryEntry
 myCol.CopyTo(myArr, 0)

 ' Displays the values in the array.
 Console.WriteLine("Displays the elements in the array:")
 Console.WriteLine(" KEY VALUE")
 Dim i As Integer
 For i = 0 To myArr.Length - 1
 Console.WriteLine(" {0,-10} {1}", myArr(i).Key, myArr(i).Value)
 Next i
 Console.WriteLine()

 ' Searches for a value.
 If myCol.ContainsValue("amarillo") Then
 Console.WriteLine("The collection contains the value ""amarillo"".")
 Else
 Console.WriteLine("The collection does not contain the value ""amarillo"".")
 End If
 Console.WriteLine()

 ' Searches for a key and deletes it.
 If myCol.ContainsKey("green") Then
 myCol.Remove("green")
 End If
 Console.WriteLine("The collection contains the following elements after removing ""green"":")
 PrintKeysAndValues1(myCol)

 ' Clears the entire collection.
 myCol.Clear()
 Console.WriteLine("The collection contains the following elements after it is cleared:")
 PrintKeysAndValues1(myCol)

 End Sub


 ' Uses the For Each statement which hides the complexity of the enumerator.
 ' NOTE: The For Each statement is the preferred way of enumerating the contents of a collection.
 Public Shared Sub PrintKeysAndValues1(myCol As StringDictionary)
 Console.WriteLine(" KEY VALUE")
 Dim de As DictionaryEntry
 For Each de In myCol
 Console.WriteLine(" {0,-25} {1}", de.Key, de.Value)
 Next de
 Console.WriteLine()
 End Sub


 ' Uses the enumerator. 
 ' NOTE: The For Each statement is the preferred way of enumerating the contents of a collection.
 Public Shared Sub PrintKeysAndValues2(myCol As StringDictionary)
 Dim myEnumerator As IEnumerator = myCol.GetEnumerator()
 Dim de As DictionaryEntry
 Console.WriteLine(" KEY VALUE")
 While myEnumerator.MoveNext()
 de = CType(myEnumerator.Current, DictionaryEntry)
 Console.WriteLine(" {0,-25} {1}", de.Key, de.Value)
 End While
 Console.WriteLine()
 End Sub


 ' Uses the Keys, Values, Count, and Item properties.
 Public Shared Sub PrintKeysAndValues3(myCol As StringDictionary)
 Dim myKeys(myCol.Count) As String
 myCol.Keys.CopyTo(myKeys, 0)

 Console.WriteLine(" INDEX KEY VALUE")
 Dim i As Integer
 For i = 0 To myCol.Count - 1
 Console.WriteLine(" {0,-5} {1,-25} {2}", i, myKeys(i), myCol(myKeys(i)))
 Next i
 Console.WriteLine()
 End Sub

End Class


'This code produces the following output.
'
'Displays the elements using For Each:
' KEY VALUE
' red rojo
' blue azul
' green verde
'
'Displays the elements using the IEnumerator:
' KEY VALUE
' red rojo
' blue azul
' green verde
'
'Displays the elements using the Keys, Values, Count, and Item properties:
' INDEX KEY VALUE
' 0 red rojo
' 1 blue azul
' 2 green verde
'
'Displays the elements in the array:
' KEY VALUE
' red rojo
' blue azul
' green verde
'
'
'The collection does not contain the value "amarillo".
'
'The collection contains the following elements after removing "green":
' KEY VALUE
' red rojo
' blue azul
'
'The collection contains the following elements after it is cleared:
' KEY VALUE

Remarks

A key cannot be null, but a value can.

The key is handled in a case-insensitive manner; it is translated to lowercase before it is used with the string dictionary.

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 Performing Culture-Insensitive String Operations.

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 StringDictionary, but derived classes can create their own synchronized versions of the StringDictionary using the SyncRoot property.

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.

See also

• Hashtable
• Performing Culture-Insensitive String Operations