Question

I have a Javascript statement in an MVC view that looks like this and works:

win.attachURL('<%: Url.Action("GraphDetails", "Dashboard", new { area = "Anglian", OSName = "Hello" }) %>');

When I try to extract the variable ‘Hello’ and put it into a javascript variable (id) and subsequently embed it into my tag like this, it breaks:

var id = "Hello";
win.attachURL('<%: Url.Action("GraphDetails", "Dashboard", new { area = "Anglian", OSName = "' + id + '" }) %>');

Question is, how do I embed a JS variable inside an ASP server tag, that itself is already embedded within Javascript? This is for a local prototype, security concerns are not an issue.

Thank you,

Tom.

Answer 1

I don’t think you can in general. In this case at least the <%: … %> part is evaluated at page load time and will never run again.

Instead, you can compute this in JavaScript, e.g.

var id = "Hello";
var baseURL = '<%: Url.Action("GraphDetails", "Dashboard",
                              new { area = "Anglian" }) %>';
win.attachURL(baseURL + '&OSName=' + id);

However that makes assumptions about how you’re assembling your routing parameters for that route. You could use Url.Action to generate the full route with a dummy value and then substitute, e.g.

var id = "Hello";
var baseURL = '<%: Url.Action("GraphDetails", "Dashboard",
                              new { area = "Anglian", OSName="ZZZ" }) %>';
win.attachURL(baseURL.replace('ZZZ', id);

but then there’s a subtle chance this could go wrong, particularly if you’re feeding user generated string into other parameters in the string where they could hit on the value you substitute.

If you really did want to run Url.Action again you’d have to make an AJAX call back to a known URL with the parameters to get the URL, which is overkill really.