How to access javascript variable within @URL.Action()

In the same vein as Brian Mains's answer, you could format your url string instead of replacing -1 with your variable, that is if like me, you judge it is better to read. The following answer assumes that you've modified String's prototype as suggested in this answer:

var url = unescape('@Url.Action("download file", "download", new { id = "{0}" })').format(myjavascriptID);

The unescape call is necessary if you want to decode your {0}. I like this alternative, because it makes it easier to have multiple parameters from JS variables. For instance:

var url = unescape('@Html.Raw(Url.Action("Action", "Controller", new { id = "{0}", name = "{1}" }))').format(myID, myName);

I added Html.Raw in my second example in order to avoid having &amp in the url string.

You can pass in the variables to any link as shown below...

var url = '@Html.Raw(@Url.Action("MethodName", "ControllerName"))' + '?id = ' + myjavascriptID

You can't. JavaScript doesn't execute when generating the action URL. What you can do, is do something like this:

function name(myjavascriptID)    {
     var link = '@Url.Action("download file", "download", new { id = "-1" })';
     link = link.replace("-1", myjavascriptID);

     jQuery("#list_d").jqGrid('setGridParam', { url: link, page: 1 });
}

I do something fairly similar, but less verbose:

var myUrl = '@Url.Action("Solution","Partner")/' + myjavascriptID;
$.ajax.load(myUrl); // or whatever

We can do this because of routing, and ultimately Url.Action with route dictionary parameters translates into a URI that looks like:

http://localhost:41215/Partner/Solution?myJavascriptID=7

Just a second choice, because as a wise old man once said "It is our choices, Harry, that show what we truly are, far more than our abilities."