Was this page helpful?
Your feedback about this content is important. Let us know what you think.
Additional feedback?
1500 characters remaining
Clear Method

Hashtable.Clear Method

Removes all elements from the Hashtable.

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

'Declaration
Public Overridable Sub Clear
'Usage
Dim instance As Hashtable

instance.Clear
public void Clear ()
public function Clear ()
Not applicable.

Exception typeCondition

NotSupportedException

The Hashtable is read-only.

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.

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

Imports System
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", "jumped")

        ' Displays the count and values of the Hashtable.
        Console.WriteLine("Initially,")
        Console.WriteLine("   Count    : {0}", 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    : {0}", myHT.Count)
        Console.WriteLine("   Values:")
        PrintKeysAndValues(myHT)

    End Sub 'Main


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

End Class 'SamplesHashtable 


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


import System.*;
import System.Collections.*;

public class SamplesHashtable
{
    public static void main(String[] args)
    {
        // Creates and initializes a new Hashtable.
        Hashtable myHT = new Hashtable();

        myHT.Add("one", "The");
        myHT.Add("two", "quick");
        myHT.Add("three", "brown");
        myHT.Add("four", "fox");
        myHT.Add("five", "jumped");

        // Displays the count and values of the Hashtable.
        Console.WriteLine("Initially,");
        Console.WriteLine("   Count    : {0}", 
            System.Convert.ToString(myHT.get_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    : {0}", 
            System.Convert.ToString(myHT.get_Count()));
        Console.WriteLine("   Values:");
        PrintKeysAndValues(myHT);
    } //main

    public static void PrintKeysAndValues(Hashtable myHT)
    {
        Console.WriteLine("\t-KEY-\t-VALUE-");
        IEnumerator myEnumerator = myHT.GetEnumerator();

		while (myEnumerator.MoveNext()) {
			DictionaryEntry de = (DictionaryEntry)myEnumerator.get_Current();
            Console.WriteLine("\t{0}:\t{1}", de.get_Key(), de.get_Value());
        }
        Console.WriteLine();
    } //PrintKeysAndValues
} //SamplesHashtable 

/* 
 This code produces the following output.
 
 Initially,
    Count    : 5
    Values:
         -KEY-   -VALUE-
         two:    quick
         three:  brown
         four:   fox
         five:   jumped
         one:    The

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

import System
import System.Collections
import Microsoft.VisualBasic

// Creates and initializes a new Hashtable.
var myHT : Hashtable = new Hashtable()
myHT.Add("one", "The")
myHT.Add("two", "quick")
myHT.Add("three", "brown")
myHT.Add("four", "fox")
myHT.Add("five", "jumped")

// Displays the count and values of the Hashtable.
Console.WriteLine("Initially,")
Console.WriteLine("   Count    : {0}", 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    : {0}", myHT.Count)
Console.WriteLine("   Values:")
PrintKeysAndValues(myHT)
    
function PrintKeysAndValues(myList : Hashtable){
    var myEnumerator : IDictionaryEnumerator = myList.GetEnumerator()
    Console.WriteLine("\t-KEY-\t-VALUE-")
    while(myEnumerator.MoveNext())
        Console.WriteLine("\t{0}:\t{1}", myEnumerator.Key, myEnumerator.Value)
    Console.WriteLine()
}

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

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

XNA Framework

Supported in: 1.0

Community Additions

ADD
Show:
© 2015 Microsoft