DictionaryBase Class

 

Provides the abstract base class for a strongly typed collection of key/value pairs.

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


[SerializableAttribute]
[ComVisibleAttribute(true)]
public abstract class DictionaryBase : IDictionary, ICollection, 
	IEnumerable

NameDescription
System_CAPS_protmethodDictionaryBase()

Initializes a new instance of the DictionaryBase class.

NameDescription
System_CAPS_pubpropertyCount

Gets the number of elements contained in the DictionaryBase instance.

System_CAPS_protpropertyDictionary

Gets the list of elements contained in the DictionaryBase instance.

System_CAPS_protpropertyInnerHashtable

Gets the list of elements contained in the DictionaryBase instance.

NameDescription
System_CAPS_pubmethodClear()

Clears the contents of the DictionaryBase instance.

System_CAPS_pubmethodCopyTo(Array, Int32)

Copies the DictionaryBase elements to a one-dimensional Array at the specified index.

System_CAPS_pubmethodEquals(Object)

Determines whether the specified object is equal to the current object.(Inherited from Object.)

System_CAPS_protmethodFinalize()

Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.(Inherited from Object.)

System_CAPS_pubmethodGetEnumerator()

Returns an IDictionaryEnumerator that iterates through the DictionaryBase instance.

System_CAPS_pubmethodGetHashCode()

Serves as the default hash function. (Inherited from Object.)

System_CAPS_pubmethodGetType()

Gets the Type of the current instance.(Inherited from Object.)

System_CAPS_protmethodMemberwiseClone()

Creates a shallow copy of the current Object.(Inherited from Object.)

System_CAPS_protmethodOnClear()

Performs additional custom processes before clearing the contents of the DictionaryBase instance.

System_CAPS_protmethodOnClearComplete()

Performs additional custom processes after clearing the contents of the DictionaryBase instance.

System_CAPS_protmethodOnGet(Object, Object)

Gets the element with the specified key and value in the DictionaryBase instance.

System_CAPS_protmethodOnInsert(Object, Object)

Performs additional custom processes before inserting a new element into the DictionaryBase instance.

System_CAPS_protmethodOnInsertComplete(Object, Object)

Performs additional custom processes after inserting a new element into the DictionaryBase instance.

System_CAPS_protmethodOnRemove(Object, Object)

Performs additional custom processes before removing an element from the DictionaryBase instance.

System_CAPS_protmethodOnRemoveComplete(Object, Object)

Performs additional custom processes after removing an element from the DictionaryBase instance.

System_CAPS_protmethodOnSet(Object, Object, Object)

Performs additional custom processes before setting a value in the DictionaryBase instance.

System_CAPS_protmethodOnSetComplete(Object, Object, Object)

Performs additional custom processes after setting a value in the DictionaryBase instance.

System_CAPS_protmethodOnValidate(Object, Object)

Performs additional custom processes when validating the element with the specified key and value.

System_CAPS_pubmethodToString()

Returns a string that represents the current object.(Inherited from Object.)

NameDescription
System_CAPS_pubinterfaceSystem_CAPS_privmethodIDictionary.Add(Object, Object)

Adds an element with the specified key and value into the DictionaryBase.

System_CAPS_pubinterfaceSystem_CAPS_privmethodIDictionary.Contains(Object)

Determines whether the DictionaryBase contains a specific key.

System_CAPS_pubinterfaceSystem_CAPS_privmethodIDictionary.Remove(Object)

Removes the element with the specified key from the DictionaryBase.

System_CAPS_pubinterfaceSystem_CAPS_privmethodIEnumerable.GetEnumerator()

Returns an IEnumerator that iterates through the DictionaryBase.

System_CAPS_pubinterfaceSystem_CAPS_privpropertyICollection.IsSynchronized

Gets a value indicating whether access to a DictionaryBase object is synchronized (thread safe).

System_CAPS_pubinterfaceSystem_CAPS_privpropertyICollection.SyncRoot

Gets an object that can be used to synchronize access to a DictionaryBase object.

System_CAPS_pubinterfaceSystem_CAPS_privpropertyIDictionary.IsFixedSize

Gets a value indicating whether a DictionaryBase object has a fixed size.

System_CAPS_pubinterfaceSystem_CAPS_privpropertyIDictionary.IsReadOnly

Gets a value indicating whether a DictionaryBase object is read-only.

System_CAPS_pubinterfaceSystem_CAPS_privpropertyIDictionary.Item[Object]

Gets or sets the value associated with the specified key.

System_CAPS_pubinterfaceSystem_CAPS_privpropertyIDictionary.Keys

Gets an ICollection object containing the keys in the DictionaryBase object.

System_CAPS_pubinterfaceSystem_CAPS_privpropertyIDictionary.Values

Gets an ICollection object containing the values in the DictionaryBase object.

NameDescription
System_CAPS_pubmethodAsParallel()

Overloaded. Enables parallelization of a query.(Defined by ParallelEnumerable.)

System_CAPS_pubmethodAsQueryable()

Overloaded. Converts an IEnumerable to an IQueryable.(Defined by Queryable.)

System_CAPS_pubmethodCast<TResult>()

Casts the elements of an IEnumerable to the specified type.(Defined by Enumerable.)

System_CAPS_pubmethodOfType<TResult>()

Filters the elements of an IEnumerable based on a specified type.(Defined by Enumerable.)

The foreach statement of the C# language (for each in Visual Basic) returns an object of the type of the elements in the collection. Since each element of the DictionaryBase is a key/value pair, the element type is not the type of the key or the type of the value. Instead, the element type is DictionaryEntry.

The foreach statement is a wrapper around the enumerator, which only allows reading from, not writing to, the collection.

System_CAPS_noteNote

Because keys can be inherited and their behavior changed, their absolute uniqueness cannot be guaranteed by comparisons using the Equals method.

Notes to Implementers:

This base class is provided to make it easier for implementers to create a strongly typed custom collection. Implementers are encouraged to extend this base class instead of creating their own.

Members of this base class are protected and are intended to be used through a derived class only.

The following code example implements the DictionaryBase class and uses that implementation to create a dictionary of String keys and values that have a Length of 5 characters or less.

using System;
using System.Collections;

public class ShortStringDictionary : DictionaryBase  {

   public String this[ String key ]  {
      get  {
         return( (String) Dictionary[key] );
      }
      set  {
         Dictionary[key] = value;
      }
   }

   public ICollection Keys  {
      get  {
         return( Dictionary.Keys );
      }
   }

   public ICollection Values  {
      get  {
         return( Dictionary.Values );
      }
   }

   public void Add( String key, String value )  {
      Dictionary.Add( key, value );
   }

   public bool Contains( String key )  {
      return( Dictionary.Contains( key ) );
   }

   public void Remove( String key )  {
      Dictionary.Remove( key );
   }

   protected override void OnInsert( Object key, Object value )  {
      if ( key.GetType() != typeof(System.String) )
         throw new ArgumentException( "key must be of type String.", "key" );
      else  {
         String strKey = (String) key;
         if ( strKey.Length > 5 )
            throw new ArgumentException( "key must be no more than 5 characters in length.", "key" );
      }

      if ( value.GetType() != typeof(System.String) )
         throw new ArgumentException( "value must be of type String.", "value" );
      else  {
         String strValue = (String) value;
         if ( strValue.Length > 5 )
            throw new ArgumentException( "value must be no more than 5 characters in length.", "value" );
      }
   }

   protected override void OnRemove( Object key, Object value )  {
      if ( key.GetType() != typeof(System.String) )
         throw new ArgumentException( "key must be of type String.", "key" );
      else  {
         String strKey = (String) key;
         if ( strKey.Length > 5 )
            throw new ArgumentException( "key must be no more than 5 characters in length.", "key" );
      }
   }

   protected override void OnSet( Object key, Object oldValue, Object newValue )  {
      if ( key.GetType() != typeof(System.String) )
         throw new ArgumentException( "key must be of type String.", "key" );
      else  {
         String strKey = (String) key;
         if ( strKey.Length > 5 )
            throw new ArgumentException( "key must be no more than 5 characters in length.", "key" );
      }

      if ( newValue.GetType() != typeof(System.String) )
         throw new ArgumentException( "newValue must be of type String.", "newValue" );
      else  {
         String strValue = (String) newValue;
         if ( strValue.Length > 5 )
            throw new ArgumentException( "newValue must be no more than 5 characters in length.", "newValue" );
      }
   }

   protected override void OnValidate( Object key, Object value )  {
      if ( key.GetType() != typeof(System.String) )
         throw new ArgumentException( "key must be of type String.", "key" );
      else  {
         String strKey = (String) key;
         if ( strKey.Length > 5 )
            throw new ArgumentException( "key must be no more than 5 characters in length.", "key" );
      }

      if ( value.GetType() != typeof(System.String) )
         throw new ArgumentException( "value must be of type String.", "value" );
      else  {
         String strValue = (String) value;
         if ( strValue.Length > 5 )
            throw new ArgumentException( "value must be no more than 5 characters in length.", "value" );
      }
   }

}


public class SamplesDictionaryBase  {

   public static void Main()  {

      // Creates and initializes a new DictionaryBase.
      ShortStringDictionary mySSC = new ShortStringDictionary();

      // Adds elements to the collection.
      mySSC.Add( "One", "a" );
      mySSC.Add( "Two", "ab" );
      mySSC.Add( "Three", "abc" );
      mySSC.Add( "Four", "abcd" );
      mySSC.Add( "Five", "abcde" );

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

      // Display the contents of the collection using the enumerator.
      Console.WriteLine( "Contents of the collection (using enumerator):" );
      PrintKeysAndValues2( mySSC );

      // Display the contents of the collection using the Keys property and the Item property.
      Console.WriteLine( "Initial contents of the collection (using Keys and Item):" );
      PrintKeysAndValues3( mySSC );

      // Tries to add a value that is too long.
      try  {
         mySSC.Add( "Ten", "abcdefghij" );
      }
      catch ( ArgumentException e )  {
         Console.WriteLine( e.ToString() );
      }

      // Tries to add a key that is too long.
      try  {
         mySSC.Add( "Eleven", "ijk" );
      }
      catch ( ArgumentException e )  {
         Console.WriteLine( e.ToString() );
      }

      Console.WriteLine();

      // Searches the collection with Contains.
      Console.WriteLine( "Contains \"Three\": {0}", mySSC.Contains( "Three" ) );
      Console.WriteLine( "Contains \"Twelve\": {0}", mySSC.Contains( "Twelve" ) );
      Console.WriteLine();

      // Removes an element from the collection.
      mySSC.Remove( "Two" );

      // Displays the contents of the collection.
      Console.WriteLine( "After removing \"Two\":" );
      PrintKeysAndValues1( mySSC );

   }

   // 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( ShortStringDictionary myCol )  {
      foreach ( DictionaryEntry myDE in myCol )
         Console.WriteLine( "   {0,-5} : {1}", myDE.Key, myDE.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( ShortStringDictionary myCol )  {
      DictionaryEntry myDE;
      System.Collections.IEnumerator myEnumerator = myCol.GetEnumerator();
      while ( myEnumerator.MoveNext() )
         if ( myEnumerator.Current != null )  {
            myDE = (DictionaryEntry) myEnumerator.Current;
            Console.WriteLine( "   {0,-5} : {1}", myDE.Key, myDE.Value );
         }
      Console.WriteLine();
   }

   // Uses the Keys property and the Item property.
   public static void PrintKeysAndValues3( ShortStringDictionary myCol )  {
      ICollection myKeys = myCol.Keys;
      foreach ( String k in myKeys )
         Console.WriteLine( "   {0,-5} : {1}", k, myCol[k] );
      Console.WriteLine();
   }

}


/* 
This code produces the following output.

Contents of the collection (using foreach):
   Three : abc
   Five  : abcde
   Two   : ab
   One   : a
   Four  : abcd

Contents of the collection (using enumerator):
   Three : abc
   Five  : abcde
   Two   : ab
   One   : a
   Four  : abcd

Initial contents of the collection (using Keys and Item):
   Three : abc
   Five  : abcde
   Two   : ab
   One   : a
   Four  : abcd

System.ArgumentException: value must be no more than 5 characters in length.
Parameter name: value
   at ShortStringDictionary.OnValidate(Object key, Object value)
   at System.Collections.DictionaryBase.System.Collections.IDictionary.Add(Object key, Object value)
   at SamplesDictionaryBase.Main()
System.ArgumentException: key must be no more than 5 characters in length.
Parameter name: key
   at ShortStringDictionary.OnValidate(Object key, Object value)
   at System.Collections.DictionaryBase.System.Collections.IDictionary.Add(Object key, Object value)
   at SamplesDictionaryBase.Main()

Contains "Three": True
Contains "Twelve": False

After removing "Two":
   Three : abc
   Five  : abcde
   One   : a
   Four  : abcd

*/

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

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 DictionaryBase, but derived classes can create their own synchronized versions of the DictionaryBase 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.

Return to top
Show: