disabling a button with textbox

sh_erfan · #1 (**permalink**) November 2nd, 2009, 08:37 PM

I dont' know how to disable a button when there is no text in a textbox an enable it the moment a character is enterd to textbox!!!!!!!!!

I use textChanged event but it doesn't work correctly.for example when I delete the text(I mean all characters in textbox) the button is enabled but after pressing a BackSpace it becomes disabled.

How can I overcome this problem?Is there any other events to control this?
or any other suggestions?

I need your help.....

nqsousa · #2 (**permalink**) November 4th, 2009, 03:16 PM

Try defining sub for text_changed event for textbox object which reacts to lenght of textbox object. Don't forget to set the AutoPostBack property of the TextBox to "True".

A solution in vb (page8.aspx with page8.aspx.vb as code-behind file) would be:
page8.aspx

Code:

<%@ Page Language="VB" AutoEventWireup="false" CodeFile="Page8.aspx.vb" Inherits="Page8" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    
        <asp:TextBox ID="TextBox1" runat="server" AutoPostBack="True"></asp:TextBox>
        <asp:Button ID="Button1" runat="server" Enabled="False" Text="Button" />
    
    </div>
    </form>
</body>
</html>

page8.aspx.vb

Code:

Partial Class Page8
    Inherits System.Web.UI.Page

    Protected Sub TextBox1_TextChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles TextBox1.TextChanged
        If Len(CType(sender, TextBox).Text) > 0 Then
            Button1.Enabled = True
        Else
            Button1.Enabled = False
        End If
        Button1.Focus()
    End Sub

End Class

hOPE IT HELPS

nqsousa · #3 (**permalink**) November 4th, 2009, 03:19 PM

I'm not familiar with exact code in C#, but the principle would be the same:
-create sub (void) for textbox object text-changed event that enables/disables button object
-activate postback for textbox

sh_erfan · #4 (**permalink**) November 6th, 2009, 03:24 PM

Thanks a lot.

It works correctly.I forgot to instantiate a new object of textbox.This way I get lots of extra attributes and methods.

thank you nqsousa...

Need to download code?

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