StringDictionary Class
Implements a hash table with the key and the value strongly typed to be strings rather than objects.
Assembly: System (in System.dll)
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 Comparing and Sorting Data for a Specific Culture and Performing Culture-Insensitive String Operations.
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 */
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.
Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.