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use javascript to make a textbox visible on DDL selection

maqskywalker asked
Last Modified: 2015-03-03
I'm using Visual studio 2013. I have a regulare .aspx web forms page.

So on my page i have a asp DropDownList and a ASP Textbox.

This is my code:


<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="DDL_ASP_EnableDisableTextBox1.aspx.cs" Inherits="Wizards2.DDL_ASP_EnableDisableTextBox1" %>

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title> Make TextBox Visible on DDL Selection</title>

    <script type="text/javascript">

        // disable textbox by default
        //Textbox1.disabled = true;
        document.getElementById('TextBox1').style.visibility = 'hidden';

        function Enable() {

            document.getElementById('TextBox1').style.visibility = 'visible';
            //document.getElementById("TextBox1").disabled = false;

    <form id="form1" runat="server">
        <asp:DropDownList ID="DropDown_Fruit" runat="server" AutoPostBack="True" onchange="Enable();">
        <br /><br /><br /><br />                  
        <asp:TextBox runat="server" ID="TextBox1" />       


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This is what I want:

When the page launches I want TextBox1 to be hidden.
Then if I select any item from the Drop Down List then I want the textbox to become visible.

Where am I making a mistake in my code above?
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