StringDictionary Class
Implements a hash table with the key and the value strongly typed to be strings rather than objects.
Namespace: System.Collections.Specialized
Assembly: System (in System.dll)
The StringDictionary type exposes the following members.
| Name | Description | |
|---|---|---|
![]() ![]() | Count | Gets the number of key/value pairs in the StringDictionary. |
![]() ![]() | IsSynchronized | Gets a value indicating whether access to the StringDictionary is synchronized (thread safe). |
![]() ![]() | Item | Gets or sets the value associated with the specified key. |
![]() ![]() | Keys | Gets a collection of keys in the StringDictionary. |
![]() ![]() | SyncRoot | Gets an object that can be used to synchronize access to the StringDictionary. |
![]() ![]() | Values | Gets a collection of values in the StringDictionary. |
| Name | Description | |
|---|---|---|
![]() ![]() | Add | Adds an entry with the specified key and value into the StringDictionary. |
![]() ![]() | Clear | Removes all entries from the StringDictionary. |
![]() ![]() | ContainsKey | Determines if the StringDictionary contains a specific key. |
![]() ![]() | ContainsValue | Determines if the StringDictionary contains a specific value. |
![]() ![]() | CopyTo | Copies the string dictionary values to a one-dimensional Array instance at the specified index. |
![]() ![]() | Equals(Object) | Determines whether the specified object is equal to the current object. (Inherited from Object.) |
![]() ![]() | Finalize | Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.) |
![]() ![]() | GetEnumerator | Returns an enumerator that iterates through the string dictionary. |
![]() ![]() | GetHashCode | Serves as a hash function for a particular type. (Inherited from Object.) |
![]() ![]() | GetType | Gets the Type of the current instance. (Inherited from Object.) |
![]() ![]() | MemberwiseClone | Creates a shallow copy of the current Object. (Inherited from Object.) |
![]() ![]() | Remove | Removes the entry with the specified key from the string dictionary. |
![]() ![]() | ToString | Returns a string that represents the current object. (Inherited from Object.) |
| Name | Description | |
|---|---|---|
![]() | AsParallel | Enables parallelization of a query. (Defined by ParallelEnumerable.) |
![]() | AsQueryable | Converts an IEnumerable to an IQueryable. (Defined by Queryable.) |
![]() ![]() | Cast<TResult> | Casts the elements of an IEnumerable to the specified type. (Defined by Enumerable.) |
![]() ![]() | OfType<TResult> | Filters the elements of an IEnumerable based on a specified type. (Defined by Enumerable.) |
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 */
Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
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.




