ASP.Net - TextBox_TextChanged not working

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In my Asp.Net project, I tried to use JavaScript to catch the text change. the related code are below:

XML

<script type="text/javascript">
     function txtMsg_TextChanged(txt) {
         //alert("Hi!");
         var s = txtMessage.toString();
     }
</script>

XML

<asp:TextBox ID="txtMessage"
                runat="server"
                Columns="40"
                Rows="6" AutoPostBack="True"
                TextMode="MultiLine" ontextchanged="txtMessage_TextChanged"
                onchange="txtMsg_TextChanged(this)" >
</asp:TextBox>

In Code behind, Page_Load()

C#

if (!Page.IsPostBack) {
    txtMessage.Attributes.Add("onchange", "txtMsg_TextChanged();
}"

When I debugged the code on the function txtMsg_TextChanged(txt), I got a warning. Then I checked both variables: txt, and txtMessage - both of them have no value. How can get the value of txtMessage that I typed in the textbox? Thanks.

Posted 24-Oct-13 7:14am

Member 10454592

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Zafar Sultan · Answer 1 · 2013-10-24T18:17:00

Add this script in the head section:

JavaScript

<script type="text/javascript">
function ChangeText(obj) {
    alert(obj.value);
}
</script>

This is the markup for the textbox:

ASP.NET

<asp:textbox id="myTextBox" runat="server" autopostback="true" ontextchanged="myTextBox_TextChanged"></asp:textbox>

And this is the code behind:

C#

if (!IsPostBack)
{
    myTextBox.Attributes.Add("onchange", "ChangeText(this);");
}
protected void myTextBox_TextChanged(object sender, EventArgs e)
{
    Response.Write(myTextBox.Text);
}

Harshil_Raval · Answer 2 · 2013-10-24T18:38:00

Hi,
As you want to catch text change event on javascript side, you have two options.
1. Use onchange event. This event will fire javascript function as you loose focus from textbox.
2. Use keyup event, it will fire javascript function on each and every key up event.

Note:- As you don't want to fire server side event, do not use AutoPostBack="true" in textbox.

ASP.NET

<!-- Your Markup-->
<asp:textbox id="txtMessage" runat="server" columns="40" rows="6" textmode="MultiLine" onchange="txtMsg_TextChanged(this)" ></asp:textbox>
<asp:textbox id="txtMessage1" runat="server" columns="40" rows="6" textmode="MultiLine" onkeyup="txtMsg_TextChanged1(this)" ></asp:textbox>

<script type="text/javascript">
     // this function is called as you loose focus from textbox "txtMessage"
     function txtMsg_TextChanged(a) {
         alert(a.value);
     }

     // this function is called on every keyup event of textbox "txtMessage1"
     function txtMsg_TextChanged1(a) {
         alert(a.value);
     }
</script>

Try both, use as per your need.
Hope it helps you.
Thanks.

Ranjan.D · Answer 3 · 2013-10-24T07:25:00

Solution 1

Use Jquery Get Element By ID or It can also be done with bare javascript.

C#

function txtMsg_TextChanged(txt) {
        //alert("Hi!");
        var s = $(txt).val()
    }

http://www.w3schools.com/jquery/sel_id.asp[^]

Posted 24-Oct-13 7:25am

Ranjan.D

Updated 24-Oct-13 7:27am

v5

**VICK** · Answer 4 · 2013-10-24T18:41:00

If you want to call a javascript function on Textbox textchange event.
Than you can use the following in design side.

C#

<asp:textbox id="txt1" runat="server" ontextchanged="javascript:Jfunction(this);" xmlns:asp="#unknown"></asp:textbox>

and in the head in script tag.

use..

JavaScript

function Jfunction(txtbx)

{


}

Hope it will help. :)

ASP.Net - TextBox_TextChanged not working

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