StringDictionary.ContainsKey Method (String)


Determines if the StringDictionary contains a specific key.

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

public virtual bool ContainsKey(
	string key


Type: System.String

The key to locate in the StringDictionary.

Return Value

Type: System.Boolean

true if the StringDictionary contains an entry with the specified key; otherwise, false.

Exception Condition

The key is null.

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

This method is an O(1) operation.

Starting with the .NET Framework 2.0, this method uses the collection’s objects’ Equals and CompareTo methods on item to determine whether item exists. In the earlier versions of the .NET Framework, this determination was made by using the Equals and CompareTo methods of the item parameter on the objects in the collection.

The following code example searches for an element in 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" );

      // Displays the values in the StringDictionary.
      Console.WriteLine( "Initial contents of the StringDictionary:" );
      PrintKeysAndValues( myCol );

      // Searches for a key.
      if ( myCol.ContainsKey( "red" ) )
         Console.WriteLine( "The collection contains the key \"red\"." );
         Console.WriteLine( "The collection does not contain the key \"red\"." );

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


   public static void PrintKeysAndValues( StringDictionary myCol )  {
      Console.WriteLine( "   KEY        VALUE" );
      foreach ( DictionaryEntry de in myCol )
         Console.WriteLine( "   {0,-10} {1}", de.Key, de.Value );


This code produces the following output.

Initial contents of the StringDictionary:
   KEY        VALUE
   green      verde
   red        rojo
   blue       azul

The collection contains the key "red".

The collection does not contain the value "amarillo".


Universal Windows Platform
Available since 10
.NET Framework
Available since 1.1
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