Asp Control ASP.Net

<%@ Page Language="VB" %>

    Sub mapMenu_Click(ByVal sender As Object, ByVal e As ImageMapEventArgs)
        Select Case e.PostBackValue
            Case "ToUpper"
                txtText.Text = txtText.Text.ToUpper()
            Case "ToLower"
                txtText.Text = txtText.Text.ToLower()
            Case "Erase"
                txtText.Text = String.Empty
        End Select
    End Sub



    ImageMap PostBack


    
    

    
            id="mapMenu"
        ImageUrl="http://www.rntsoft.com/style/logo.png"
        HotSpotMode="PostBack"
        Runat="server" OnClick="mapMenu_Click">
                    PostBackValue="ToUpper"
            Left="0"
            Top="0"
            Right="100"
            Bottom="30"
            AlternateText="To Uppercase" />
                    PostBackValue="ToLower"
            Left="100"
            Top="0"
            Right="200"
            Bottom="30"
            AlternateText="To Uppercase" />
                    PostBackValue="Erase"
            Left="200"
            Top="0"
            Right="300"
            Bottom="30"
            AlternateText="To Uppercase" />
    
    
    
    
            id="txtText"
        TextMode="MultiLine"
        Columns="40"
        Rows="5"
        Runat="server" />