Get textbox value after changing with javascript

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Changing the value of a textbox via javascript on dropdownlist change (no postback). Textbox updates properly but the value does not come through when the form is submitted. I assume this is because the javascript change is only happening on the client side? How can I get this value on server side?

What I have tried:

<pre>  <script type="text/javascript">
      function ddlChange() {
          var ddl = document.getElementById('<%=DDLg4corp.ClientID %>');
          var textBox = document.getElementById('<%= txtg4action.ClientID%>');

          textBox.value = ddl.options[ddl.selectedIndex].value;
      }
</script>

<asp:DropDownList runat="server" ID="DDLg4corp" onchange="ddlChange();">
  <asp:ListItem Value="1" Text="Option 1"></asp:ListItem>
  <asp:ListItem Value="2" Text="Option 2"></asp:ListItem>
  <asp:ListItem Value="3" Text="Option 3"></asp:ListItem>
  <asp:ListItem Value="4" Text="Option 4"></asp:ListItem>
</asp:DropDownList>

<asp:TextBox runat="server" id="txtg4action"></asp:TextBox>

 Private Sub Button_Click(sender As Object, e As EventArgs) Handles btnSubmit1.Click,


With update
  .Connection = connection
  .CommandType = CommandType.Text
    If qrtSelect.SelectedValue = 1 Then
       .CommandText = "Update table set txtg4action=@txtg4action where users=@users"
       .Parameters.AddWithValue("@txtg4action", txtg4action.Text)

Posted 4-Jan-18 5:26am

Member 9388700

Updated 4-Jan-18 9:11am

v3

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Comments

A_Griffin 4-Jan-18 11:48am

On the face of it there's nothing wrong with that. YOu must be doing something else somewhere else that's causing your issue.

Member 9388700 4-Jan-18 11:54am

When I get the value of txtg4action in vb, it returns an old value; not the value from the DDL. Edited and added some more code.

A_Griffin 4-Jan-18 12:28pm

Well I don't know but the code you have will post back the selected value. Unless you maybe have EnableViewState = False in your page, maybe?

Member 9388700 4-Jan-18 13:36pm

Screenshot of the debug: https://imgur.com/a/lozni

txtg4action.text should be "2". It displays as 2 on the page but when submitted, it still has the old value. Not sure where else to look or where else I could be going wrong. Do not have EnableViewState = False

A_Griffin 4-Jan-18 13:45pm

WHat about in your page_load event? Are you re-setting its value there, not taking account of the PostBack?

Member 9388700 4-Jan-18 13:58pm

Using the script so I don't have to postback with the DDL. Nothing is getting reset on page load. It just seems like the value never makes it to the code behind. I'm new at this so apologies if I'm not making much sense.

A_Griffin 4-Jan-18 14:53pm

Well, presumably you're posting back somehow - via a button or something - that's what submitting the form is... IDK, but the code you posted is fine. I can post (as a "solution") a complete simple page using it to prove it, if you want...

Member 9388700 4-Jan-18 15:03pm

I found an ugly workaround to get the desires outcome. I'd accept a solution if you post it.

Bryian Tan 4-Jan-18 12:47pm

Yeah, I don't see any issue either. Maybe you missed some detail information in the post. Anyway, the dynamic query in your post is very contagious and open to potential SQL injection try avoid that if possible and use parameterized query. Here is a sample on how to replicate SQL injection based on your current code. I hope this will convince you. SQL Injection and Cross-Site Scripting[^]

A_Griffin 4-Jan-18 13:12pm

? he's used a parameterized query ...?

Bryian Tan 4-Jan-18 13:49pm

my bad :) sorry.

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A_Griffin · Accepted Answer · 2018-01-04T09:11:00

Well, as promised, here's a simple page using your code:

VB

<%@ Page Language="VB" %>
<script runat="server"> 
    Private Sub btnGo_Click(ByVal Sender As Object, ByVal e As EventArgs)
      litX.Text = "You selected " & txtg4action.Text
    End Sub
</script>
<html>
<head>
   <title></title> 
   <script type="text/javascript">
      function ddlChange() {
         var ddl = document.getElementById('<%=DDList.ClientID %>');
            var textBox = document.getElementById('<%= txtg4action.ClientID%>');
            textBox.value = ddl.options[ddl.selectedIndex].value;
         }
   </script>
</head>
<body>
    <form id="Form1" runat="server"> 	   
      <p><asp:DropDownList runat="server" ID="DDList" onchange="ddlChange();">
        <asp:ListItem Value="1" Text="Option 1"></asp:ListItem>
        <asp:ListItem Value="2" Text="Option 2"></asp:ListItem>
        <asp:ListItem Value="3" Text="Option 3"></asp:ListItem>
        <asp:ListItem Value="4" Text="Option 4"></asp:ListItem>
      </asp:DropDownList></p>
      <p><asp:TextBox runat="server" id="txtg4action"></asp:TextBox></p>  
      <p><asp:Button runat="server" ID="btnGo" OnClick="btnGo_Click" Text="Submit" /></p>
	  <p><asp:Literal runat="server" id="litX" /></p>	
    </form>
</body>
</html>