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Passing parameter to javascript function on textchange event of textbox in asp.net

I am deadly trying to make it , but no success,
Experts plz help me.

on any Text Change It is not prompting any message box

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
       
 txtpackage.Attributes.Add("onchange", "displaymessage(txtpackage.text)")
 
  End Sub
 
-----------------------
javascript code
------------------------
<html  >
<head runat="server">
    <title>Untitled Page</title>
       <script  language ="javascript" type="text/javascript" >
      function displaymessage(ch)
      {
        alert(ch);
      }
 
    </script>
</head>
<body>
 
    <form id="form1" runat="server">
    <div>
        <asp:TextBox ID="txtpackage" runat="server"></asp:TextBox>
        <asp:Label ID="Label1" runat="server" Text="Label" Width="190px"></asp:Label></div>
    </form>
</body>
</html>

Open in new window

TimCottee

Hello rajeev_23,

The .text property does not apply to an html textbox. You need to use .value instead. If this is a more complex page with nested controls, you cannot necessarily guarantee that the control name is as you expect. A safer option in fact is to use "displaymessage(this.value);"

Regards,

TimCottee

Obadiah Christopher

ya this.value should be passed....

And a better option to
txtpackage.Attributes.Add("onchange", "displaymessage(txtpackage.text)")

would be

txtpackage.Attributes.Add("onkeydown", "displaymessage(txtpackage.text)")

This will include the press of backspace also

TimCottee

informaniac,

OnChange doesn't worry about key presses of any kind, it only fires when focus moves from that control. Displaying an alert for every keypress could be a bit of a pain to handle for the user!

TimCottee

Obadiah Christopher

Ok. will rember that, but as far as I know... onblur fires when the focus moves from textbox control....

sandson

Hello rajeev_23,

by default the onchange is not fired as you type in the textbox, but only when it loses the focus (ie. when you click somewhere else in the page). So you may need to implement the event 'onkeypress' instead and as suggested by TimCottee use this.value instead of txtpackage.text

Regards,
Abdel

TimCottee

informaniac,

OnBlur does indeed fire when you lose focus, but onchange will only fire if the value of the element has changed at the same time so that you can easily differentiate between losing focus on an element that has not changed and one that has.

TimCottee

Obadiah Christopher

Oh wow.. I din't know that.....
THanks very much....

But in case I want to do something like autosuggest text box then i would have to use a onkeydown event right?

TimCottee

informaniac,

Yes you would, either onkeydown/up/press depending on what key presses you need to handle. The three handlers do not necessarily trap all key events so as you pointed out backspace needs to be trapped in keyup/down but can't be in keypress.

TimCottee

rajeev_23

ASKER

Experts,

this.value doesn't work's for it
any Expert who can solve my problem in C# or Vb in any one
now i am attaching C# code here


///onpage load
txtpackage.Attributes.Add("OnChange", "displaymessage(" + txtpackage.Text + ");");
 
//////////HTml code/////
<html xmlns="http://www.w3.org/1999/xhtml" >
 
<head id="Head1" runat="server">
    <title>Untitled Page</title>
       <script  language ="javascript" type="text/javascript" >
      function displaymessage(txtId)
      {
        alert(this.value); // to get all text in the text box
        //alert(String.fromCharCode(window.event.keyCode)); // cahracter just entered
      }
 
    </script>
         
   </head>
    
<body>
    <form id="form1" runat="server">
    <div>
        &nbsp;<table style="width: 615px; height: 412px">
            <tr>
                <td style="width: 100px">
        <asp:GridView ID="GridView1" runat="server">
        </asp:GridView>
                </td>
                <td style="width: 100px">
                </td>
                <td style="width: 100px">
                </td>
            </tr>
            <tr>
                <td style="width: 100px; height: 42px">
                </td>
                <td style="width: 100px; height: 42px">
                    <asp:TextBox ID="txtpackage" runat="server" Height="40px" Width="176px"></asp:TextBox></td>
                <td style="width: 100px; height: 42px">
                </td>
            </tr>
            <tr>
                <td style="width: 100px; height: 21px">
                </td>
                <td style="width: 100px; height: 21px">
                </td>
                <td style="width: 100px; height: 21px">
                </td>
            </tr>
        </table>
    
    </div>
    </form>
</body>
</html>

Open in new window

TimCottee

rajeev_23,

That is not what we suggested, you should return your javascript function to the way it was. It is the attribute that you need to change:

txtPackage.Attributes.Add("OnChange","displaymessage(this.value);")

TimCottee

sandson

Rajeev_23,

use the following snippets to get acces the textbox content.

///onpage load
txtpackage.Attributes.Add("onchange", "displaymessage('" + txtpackage.ClientID + "');"); // If you want the event be fired when losing focus
or
txtpackage.Attributes.Add("onkeypress", "displaymessage('" + txtpackage.ClientID + "');"); // If you want the event be fired for each key stroke
 
///HTML/JS code
       <script  language ="javascript" type="text/javascript" >
      function displaymessage(txtId)
      {
        var txt = document.getElementById(txtId);
        if( txt == null ) return;
        alert(txt.value); // to get all text in the text box
        //alert(String.fromCharCode(window.event.keyCode)); // cahracter just entered
      }
 
    </script>

Open in new window

Obadiah Christopher

The only prblm is ' is missing

txtpackage.Attributes.Add("OnChange", "displaymessage(" + txtpackage.Text + ");");

should be

txtpackage.Attributes.Add("OnChange", "displaymessage('" + txtpackage.Text + "');");

rajeev_23

ASKER

None of the above suggested code is working
I am still trying

////////////C# code
 txtpackage.Attributes.Add("onkeypress", "displaymessage('" + txtpackage.ClientID + "');");
 
////////HTML Code
<head id="Head1" runat="server">
    <title>Untitled Page</title>
       <script  language ="javascript" type="text/javascript" >
      function displaymessage(txtId)
      {
        var txt = document.getElementById(txtId);
        if( txt == null ) return;
        alert(txt.value); // to get all text in the text box
        //alert(String.fromCharCode(window.event.keyCode)); // cahracter just entered
      }
 
    </script>
         
   </head>

Open in new window

sandson

informaniac,

this solution can't work, as on page load server side the text propertie of txtpackage is empty so it will always show an empty message box. displaymessage to has to have either the actual value client side (this.value) or a reference to the html input itself (txtpackage.ClientID) so the function displaymessage can retrieve the value at runtime.

regards,
Abdel

Obadiah Christopher

Please check wht is the output of this?

txtpackage.Attributes.Add("onkeypress", "displaymessage('" + txtpackage.ClientID + "');");

<script language ="javascript" type="text/javascript" >
function displaymessage(txtId)
{
alert(txtId);
return false;
}

</script>

sandson

rajeev,

what do you get exactly using the code snippet I suggested ? a script error ? an empty message ? nothing ?

can you execute that page, then right click in your browser, choose 'View Source', then search for txtpackage (it should by <input type='text' id='...txtpackage..' ... />).

Copy and paste the search result (the input's source line) here so I can check if every thing went well from the server side to the client side.

regards,
Abdel

rajeev_23

ASKER

It is not prompting any error but thing I want to do is not happening i.e. message box on entry of every Single character in textbox

ASKER CERTIFIED SOLUTION

sandson

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sandson

oops I forgot the class closing } in my code snippet above, don't forget to add it before testing.

Best regards,
Abdel