StringDictionary.Clear Method

Definition

Namespace:

System.Collections.Specialized

Assembly:

System.Collections.Specialized.dll

Source:

StringDictionary.cs

Removes all entries from the StringDictionary.

public:
 virtual void Clear();

public virtual void Clear ();

abstract member Clear : unit -> unit
override this.Clear : unit -> unit

Public Overridable Sub Clear ()

Exceptions

NotSupportedException

The StringDictionary is read-only.

Examples

The following code example demonstrates how to add and remove elements from a StringDictionary.

#using <System.dll>

using namespace System;
using namespace System::Collections;
using namespace System::Collections::Specialized;
void PrintKeysAndValues( StringDictionary^ myCol )
{
   Console::WriteLine( "   KEY        VALUE" );
   IEnumerator^ enum0 = myCol->GetEnumerator();
   while ( enum0->MoveNext() )
   {
      DictionaryEntry^ de = safe_cast<DictionaryEntry^>(enum0->Current);
      Console::WriteLine( "   {0,-10} {1}", de->Key, de->Value );
   }

   Console::WriteLine();
}

int main()
{
   
   // Creates and initializes a new StringDictionary.
   StringDictionary^ myCol = gcnew 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 );
   
   // Deletes an element.
   myCol->Remove( "green" );
   Console::WriteLine( "The collection contains the following elements after removing \"green\":" );
   PrintKeysAndValues( myCol );
   
   // Clears the entire collection.
   myCol->Clear();
   Console::WriteLine( "The collection contains the following elements after it is cleared:" );
   PrintKeysAndValues( myCol );
}

/*
This code produces the following output.

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

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

*/

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 );

      // Deletes an element.
      myCol.Remove( "green" );
      Console.WriteLine( "The collection contains the following elements after removing \"green\":" );
      PrintKeysAndValues( myCol );

      // Clears the entire collection.
      myCol.Clear();
      Console.WriteLine( "The collection contains the following elements after it is cleared:" );
      PrintKeysAndValues( myCol );
   }

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

/*
This code produces the following output.

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

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

*/

Imports System.Collections
Imports System.Collections.Specialized

Public Class SamplesStringDictionary   

   Public Shared Sub Main()

      ' Creates and initializes a new StringDictionary.
      Dim myCol As 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)

      ' Deletes an element.
      myCol.Remove("green")
      Console.WriteLine("The collection contains the following elements after removing ""green"":")
      PrintKeysAndValues(myCol)

      ' Clears the entire collection.
      myCol.Clear()
      Console.WriteLine("The collection contains the following elements after it is cleared:")
      PrintKeysAndValues(myCol)

   End Sub

   Public Shared Sub PrintKeysAndValues(myCol As StringDictionary)
      Dim de As DictionaryEntry

      Console.WriteLine("   KEY        VALUE")
      For Each de In  myCol
         Console.WriteLine("   {0,-10} {1}", de.Key, de.Value)
      Next de
      Console.WriteLine()

   End Sub

End Class


'This code produces the following output.
'
'Initial contents of the StringDictionary:
'   KEY        VALUE
'   green      verde
'   red        rojo
'   blue       azul
'
'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
'

Remarks

This method is an O(n) operation, where n is Count.