Get variable in javascript from aspx.cs

Question

I have an aspx form called MyForm.aspx. In this form I had included a javascript file:

<script type="text/javascript" src="Scripts/MyForm.js"></script>

In MyForm.aspx.cs a have a property:

public string Username { get; set; }

How can I access this Username variable in the MyForm.js?

I tried in the following way but its not working: var username = '<%=this.Username%>'

What isn't working? Has the UserName property have a value at the time being used? — Patrick Hofman
– Patrick Hofman, Commented Jun 17, 2014 at 8:39
Yes it has. If I write the script in the .ascx, it is working, but in this .js file it doesn't. The username in javascript will have the value "<%=this.Username%>". — Szabolcs Antal
– Szabolcs Antal, Commented Jun 17, 2014 at 8:42
How is the javascript file related to your code file and it's property? — Patrick Hofman
– Patrick Hofman, Commented Jun 17, 2014 at 8:45
I think you can't, Javascript is only client-side scripting language — Mehdi Souregi
– Mehdi Souregi, Commented Jun 17, 2014 at 8:46
Do you need to pass only Username proeprty value from code-behind to your script, or some properties also? Show how the MyForm.js organized — IUnknown
– IUnknown, Commented Jun 17, 2014 at 8:50

sanepete · Accepted Answer · 2014-06-17 09:16:20Z

1

Call the javascript from a server side generic handler file:

<script type="text/javascript" src="cogs/awesomejavascript.ashx"></script>

Output all of the javascript from the handler file:

public void ProcessRequest (HttpContext ctx)
{
        ctx.Response.ContentType = "text/plain";
        StringBuilder bild = New StringBuilder;
        bild.Append("var username = " + this.username);
        ctx.Response.Write(bild.ToString);

}

If you're not comfortable with handler files you could use an ascx file.

edited Jun 17, 2014 at 9:16

answered Jun 17, 2014 at 8:55

sanepete

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2 Comments

sanepete Over a year ago

Doh! Thanks Patrick, edited but it looks like OP has his answer.

Patrick Hofman Over a year ago

Yeah. For MVC it was a decent answer. Your file handler idea is good though. +1

Rumen Jekov · Accepted Answer · 2014-06-17 08:56:59Z

0

The JavaScript engine will be unable to resolve the server <%=this.Username%> code in a JS file since the server tags are not part of its specification. These server brackets can be resolved only inside the aspx/ascx files by the ASP.NET engine.

You can create a function in the MyForm.js file that accepts as an argument the ID of the username field getUserName(userName){ return userName;} and call the function from the MyForm.aspx page like this:

[MyForm.aspx]

var username = '<%=this.Username%>';
getUserName(userName);

[MyForm.js]

getUserName(userName)
{
   return userName;
}

answered Jun 17, 2014 at 8:56

Rumen Jekov

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1 Comment

Szabolcs Antal Over a year ago

Your answer was a bit wrong but I edited it and it works. In MyForm.ascx I wrote a method:

<script>     function getUserName() {         var username = '<%=this.Username%>';         return username;     } </script>

and in MyForm.js a I called it like: getUserName(). But thanks a lot for your help! :)

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