How to assign Javascript return value in c# Code behind Variable

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Javascript:
<script>
function GetValue() {
return 10;
}
</script>

C#.NEt

protected void Page_Load(object sender, EventArgs e)
{
int Data
ClientScript.RegisterStartupScript(this.GetType(), "GetData", "a=GetValue();alert(a)", true);
Data=a;//a is Javascript Variable
}

In C# Page Load Method How to set Javascipt return value to C# Variables.

Posted 1-Jan-13 18:34pm

PotladaSatish

Updated 2-Jan-13 3:07am

v4

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Sergey Alexandrovich Kryukov · Answer 1 · 2013-01-01T18:47:00

Your JavaScript code is executed in a Web browser, only on the client site. And you C# code behind is executed only on server side, only in response to some HTTP request; these two parts of code never call one another. Right? Right!

Conclusions? You need to generate an HTTP request on client side via your JavaScript and process it on server side the way you like. There won't be any other way. In principle, the HTTP requests are generated be HTML forms, but in this case, probably the only adequate technique would be using Ajax. Please see:
http://en.wikipedia.org/wiki/Ajax_%28programming%29[^],
http://www.w3schools.com/ajax/default.asp[^].

There are different ways and frameworks used to leverage Ajax in your Web project, and in ASP.NET in particular. You can consider then all, but I would rather advice one: using jQuery. Please see:
http://en.wikipedia.org/wiki/JQuery[^],
http://jquery.com/[^].

Here is how you can use Ajax via jQuery: http://api.jquery.com/category/ajax/[^].

If you need to learn jQuery (which I would highly recommend), please start here:
http://docs.jquery.com/Tutorials:How_jQuery_Works[^],
http://docs.jquery.com/Tutorials[^].

Happy New Year!

—SA

magiccoder · Answer 2 · 2013-01-01T21:29:00

Hi
Try this,

JavaScript

//inside head tag

<script type="text/javascript">
        function test() {
            if (confirm("test")) {
                document.getElementById('<%=hdnTestValue.ClientID %>').value = "true";
            }
            else {
                document.getElementById('<%= hdnTestValue.ClientID %>').value = "false";
            }
        }
    </script>

ASP.NET

<!-- Body Tag -->

    <form id="form1" runat="server">
    <div>
    <asp:button runat="server" id="Button1" onclientclick="test()" xmlns:asp="#unknown">
            onclick="Button1_Click" Text="Submit" />



    <asp:hiddenfield runat="server" id="hdnTestValue" />


 <asp:label id="lblRvalue" runat="server"></asp:label>




    </asp:button></div>
    </form>

C#

//Code behind



  protected void Button1_Click(object sender, EventArgs e)
    {
        lblRvalue.Text = hdnTestValue.Value;
    }

Assign your value to hidden field with JavaScript and pass hidden field value to server side.

Please Mark as Answer if find helpful..

Happy coding...

Zafar Sultan · Answer 3 · 2013-01-01T21:31:00

Solution 3

Add a hidden field in your aspx page as:

ASP.NET

<asp:HiddenField ID="myHiddenField" runat="server" />

In your JavaScript function use:

XML

<script>
function GetValue() {
document.getElementById('myHiddenField').value = "10";
}
</script>

In your pageload event:

C#

int Data = Convert.ToInt32(myHiddenField.Value);

Posted 1-Jan-13 21:31pm

Zafar Sultan

Updated 2-Jan-13 3:45am

v2

Comments

PotladaSatish 2-Jan-13 7:57am

I want the javascript assign value in c# pageload method

Zafar Sultan 2-Jan-13 8:03am

And what's the problem with the above solution? It does exactly what you want.

PotladaSatish 2-Jan-13 9:09am

Yes..It Did.But in i want javascript return value in c# Page Load Method.

Zafar Sultan 2-Jan-13 9:12am

In your pageload event:
int Data = Convert.ToInt32(myHiddenField.Value);

This is what I wrote in my reply.

PotladaSatish 2-Jan-13 9:39am

I am getting this error :

'System.Web.UI.WebControls.HiddenField' does not have a public property named 'xmlns:asp'.

Zafar Sultan 2-Jan-13 9:42am

you must have copied the code from my reply. I will update the HTML for hidden field.

Zafar Sultan 2-Jan-13 9:46am

Use this: <asp:HiddenField ID="myHiddenField" runat="server" />

PotladaSatish 3-Jan-13 0:05am

I copied all code what you wrote,i got value in hidden field after ready document but in page load i am getting empty data.
Thanks for giving reply to me sir.

How to assign Javascript return value in c# Code behind Variable

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