Creating Buttons

Using buttons in Web forms is similar to using buttons in Windows forms, as you can see in the Buttons example on the CD-ROM. You can see this example at work in Figure 15.6; when you click the button labeled "Click me", the text "Hello from Visual Basic" appears in a text box.

Figure 15.6: The Buttons example.

For reference, here is WebForm1.aspx from the Buttons example:

<%@ Page Language="vb" AutoEventWireup="false" Codebehind=
"WebForm1.aspx.vb" Inherits="Buttons.WebForm1"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
  <HEAD>
    <title></title>
    <meta name="GENERATOR" content="Microsoft Visual Studio.NET 7.0">
    <meta name="CODE_LANGUAGE" content="Visual Basic 7.0">
    <meta name=vs_defaultClientScript content="JavaScript">
    <meta name=vs_targetSchema content="http://schemas.microsoft.com/
intellisense/ie5">
  </HEAD>
  <body MS_POSITIONING="GridLayout">

    <form id="Form1" method="post" runat="server">
<asp:Button id=Button1 style="Z-INDEX: 101; LEFT: 95px;
POSITION: absolute; TOP: 75px" runat="server" Text="Click me"
Width="125px" Height="24px"></asp:Button>
<asp:TextBox id=TextBox2 style="Z-INDEX: 104; LEFT: 239px;
POSITION: absolute; TOP: 127px" runat="server"></asp:TextBox>
<asp:Button id=Button2 style="Z-INDEX: 103; LEFT: 95px;
POSITION: absolute; TOP: 125px" runat="server" Text="Click me too"
Width="125px" Height="24px" CommandArgument="You clicked Button2"
CommandName="Button2"></asp:Button>
<asp:TextBox id=TextBox1 style="Z-INDEX: 102; LEFT: 239px; POSITION:
absolute; TOP: 76px" runat="server"></asp:TextBox>

    </form>

  </body>
</HTML>

And here is WebForm1.aspx.vb, which holds the Visual Basic code in the Buttons example:

Public Class WebForm1
    Inherits System.Web.UI.Page
    Protected WithEvents Button1 As System.Web.UI.WebControls.Button
    Protected WithEvents Button2 As System.Web.UI.WebControls.Button
    Protected WithEvents TextBox2 As System.Web.UI.WebControls.TextBox
    Protected WithEvents TextBox1 As System.Web.UI.WebControls.TextBox

#Region " Web Form Designer Generated Code "

    'This call is required by the Web Form Designer.
    <System.Diagnostics.DebuggerStepThrough()> Private Sub
InitializeComponent()

    End Sub

    Private Sub Page_Init(ByVal sender As System.Object, ByVal e As _
        System.EventArgs) Handles MyBase.Init
        'CODEGEN: This method call is required by the Web Form Designer
        'Do not modify it using the code editor.
        InitializeComponent()
    End Sub

#End Region
    Private Sub Page_Load(ByVal sender As System.Object, ByVal e As _
        System.EventArgs) Handles MyBase.Load
        'Put user code to initialize the page here
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
        System.EventArgs) Handles Button1.Click
        TextBox1.Text = "Hello from Visual Basic"
    End Sub

    Private Sub Button2_Command(ByVal sender As Object, ByVal e As _
        System.Web.UI.WebControls.CommandEventArgs) Handles Button2.Command
        TextBox2.Text = e.CommandArgument
    End Sub
End Class

By default, buttons are supported as HTML Submit buttons; here is the actual HTML sent from the server to the Web browser:

<input type="submit" name="Button1" value="Click me" id="Button1"
style="height:24px;width:125px;Z-INDEX: 101; LEFT: 95px; POSITION:
absolute; TOP: 75px" />

In the Visual Basic code, you can handle the button's Click event just as you would in a Windows form; just double-click a button to bring up this code in a code designer:

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
        System.EventArgs) Handles Button1.Click
        ⋮
    End Sub

This is reassuringly like what Windows programmers are used to, even though this button will appear in a Web browser. To display the text in the text box you see in Figure 15.6, you only need to add this code to the event handler and run the application:

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
        System.EventArgs) Handles Button1.Click
        TextBox1.Text = "Hello from Visual Basic"
    End Sub