This documentation is archived and is not being maintained.

StringDictionary.Item Property

Gets or sets the value associated with the specified key.

Namespace: System.Collections.Specialized
Assembly: System (in system.dll)

public virtual string this [
	string key
] { get; set; }
/** @property */
public String get_Item (String key)

/** @property */
public void set_Item (String key, String value)

Not applicable.

Parameters

key

The key whose value to get or set.

Property Value

The value associated with the specified key. If the specified key is not found, Get returns a null reference (Nothing in Visual Basic), and Set creates a new entry with the specified key.

Exception typeCondition

ArgumentNullException

key is a null reference (Nothing in Visual Basic).

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

A key cannot be a null reference (Nothing in Visual Basic), but a value can. To distinguish between a null reference (Nothing in Visual Basic) that is returned because the specified key is not found and a null reference (Nothing in Visual Basic) that is returned because the value of the specified key is a null reference (Nothing in Visual Basic), use the ContainsKey method to determine if the key exists in the list.

The C# language uses the this keyword to define the indexers instead of implementing the Item property. Visual Basic implements Item as a default property, which provides the same indexing functionality.

Retrieving the value of this property is an O(1) operation; setting the property is also an O(1) operation.

The following code example enumerates the elements of a 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 );

   }

   // 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

*/

import System.*;
import System.Collections.* ;
import System.Collections.Specialized.*;

public class SamplesStringDictionary
{
    public static void main(String[] args)
    {
        // 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 for loop. This is the 
        // preferred method.
        Console.WriteLine("Displays the elements using for loop:");
        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);
    } //main
       
    // Uses the for statement which hides the complexity of the enumerator.
    // NOTE: The for statement is the preferred way of enumerating the 
    // contents of a collection.
    public static void PrintKeysAndValues1(StringDictionary myCol) 
    {
        String strValue;
        String strKeys[] = new String[myCol.get_Count()];
        myCol.get_Keys().CopyTo(strKeys, 0);
        
        Console.WriteLine("   KEY                       VALUE");
        for (int iCtr = 0; iCtr < myCol.get_Count(); iCtr++) {
            strValue = myCol.get_Item(strKeys[iCtr]);
            Console.WriteLine("   {0,-25} {1}", strKeys[iCtr], strValue);
        }
        Console.WriteLine();
    } //PrintKeysAndValues1
       
    // Uses the enumerator. 
    // NOTE: The for 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.get_Current());
            Console.WriteLine("   {0,-25} {1}", de.get_Key(), de.get_Value());
        }
        Console.WriteLine();
    } //PrintKeysAndValues2
              
    // Uses the Keys, Values, Count, and Item properties.
    public static void PrintKeysAndValues3(StringDictionary myCol) 
    {
        String myKeys[] = new String[myCol.get_Count()];
        myCol.get_Keys().CopyTo(myKeys, 0);
          
        Console.WriteLine("   INDEX KEY                       VALUE");
        for(int i = 0; i < myCol.get_Count(); i++) {
            Console.WriteLine("   {0,-5} {1,-25} {2}", (Int32)i, myKeys[i],
                myCol.get_Item( myKeys[i]));
        } 
        Console.WriteLine();
    } //PrintKeysAndValues3
} //SamplesStringDictionary

/*
Displays the elements using for loop:
   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
*/

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0

XNA Framework

Supported in: 1.0
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