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Hashtable.Clear Method

Definition

Namespace:
System.Collections
Assemblies:
mscorlib.dll, System.Collections.NonGeneric.dll
Assemblies:
netstandard.dll, System.Runtime.dll
Assembly:
System.Collections.NonGeneric.dll
Assembly:
System.Runtime.Extensions.dll
Assembly:
mscorlib.dll
Assembly:
netstandard.dll
Source:
Hashtable.cs
Source:
Hashtable.cs
Source:
Hashtable.cs
Source:
Hashtable.cs

Removes all elements from the Hashtable.

public:
 virtual void Clear();
public virtual void Clear();
abstract member Clear : unit -> unit
override this.Clear : unit -> unit
Public Overridable Sub Clear ()

Implements

Clear()

Exceptions

NotSupportedException

The Hashtable is read-only.

Examples

The following example shows how to clear the values of the Hashtable.

using System;
using System.Collections;
public class SamplesHashtable
{

   public static void Main()
   {
      // Creates and initializes a new Hashtable.
      var myHT = new Hashtable();
      myHT.Add("one", "The");
      myHT.Add("two", "quick");
      myHT.Add("three", "brown");
      myHT.Add("four", "fox");
      myHT.Add("five", "jumps");

      // Displays the count and values of the Hashtable.
      Console.WriteLine("Initially,");
      Console.WriteLine($"   Count    : {myHT.Count}");
      Console.WriteLine("   Values:");
      PrintKeysAndValues(myHT);

      // Clears the Hashtable.
      myHT.Clear();

      // Displays the count and values of the Hashtable.
      Console.WriteLine("After Clear,");
      Console.WriteLine("   Count    : {myHT.Count}");
      Console.WriteLine("   Values:" );
      PrintKeysAndValues(myHT);
   }

   public static void PrintKeysAndValues( Hashtable myHT )
   {
      Console.WriteLine("\t-KEY-\t-VALUE-");
      foreach (DictionaryEntry de in myHT)
         Console.WriteLine("\t{de.Key}:\t{de.Value}");
      Console.WriteLine();
   }
}


/*
This code produces the following output.

Initially,
   Count    : 5
   Values:
        -KEY-   -VALUE-
        two:    quick
        three:  brown
        four:   fox
        five:   jumps
        one:    The

After Clear,
   Count    : 0
   Values:
        -KEY-   -VALUE-

*/

Imports System.Collections

Public Class SamplesHashtable

    Public Shared Sub Main()

        ' Creates and initializes a new Hashtable.
        Dim myHT As New Hashtable()
        myHT.Add("one", "The")
        myHT.Add("two", "quick")
        myHT.Add("three", "brown")
        myHT.Add("four", "fox")
        myHT.Add("five", "jumps")

        ' Displays the count and values of the Hashtable.
        Console.WriteLine("Initially,")
        Console.WriteLine($"   Count    : {myHT.Count}")
        Console.WriteLine("   Values:")
        PrintKeysAndValues(myHT)

        ' Clears the Hashtable.
        myHT.Clear()

        ' Displays the count and values of the Hashtable.
        Console.WriteLine("After Clear,")
        Console.WriteLine($"   Count    : {myHT.Count}")
        Console.WriteLine("   Values:")
        PrintKeysAndValues(myHT)

    End Sub


    Public Shared Sub PrintKeysAndValues(myHT As Hashtable)
        Console.WriteLine(vbTab + "-KEY-" + vbTab + "-VALUE-")
        For Each de As DictionaryEntry In myHT
            Console.WriteLine(vbTab + "{0}:" + vbTab + "{1}", de.Key, de.Value)
        Next
        Console.WriteLine()
    End Sub

End Class


' This code produces the following output.
' 
' Initially,
'    Count    : 5
'    Values:
'         -KEY-   -VALUE-
'         two:    quick
'         five:   jumps
'         one:    The
'         three:  brown
'         four:   fox
'
' After Clear,
'    Count    : 0
'    Values:
'         -KEY-   -VALUE-
'

Remarks

Count is set to zero, and references to other objects from elements of the collection are also released. The capacity remains unchanged.

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

Applies to

See also