The Digital Tool Factory Blog

The Problem

You have created a lovely model in asp.net mvc 4, using Entity Framework and a whole host of attributes.  One of the properties of your model looks like this

[Required]
[Display(Name = “Expiration Month (MM)”)]
[StringLength(2,ErrorMessage = “You must enter two digits”, MinimumLength = 1)]
[Range(1,12, ErrorMessage = “You must enter a valid month”)]
public int ExpirationMonth { get; set; }

That yields an error of

Unable to cast object of type ‘System.Int32’ to type ‘System.String

When the form is submitted, but not when the object is created (which is a bit odd)

The Cause

It turns out that you cannot use the StringLength data attribute on an int data type.  You would think you could since all you are actually interested in with that data attribute is the number of digits, but the data gods have decreed that you can’t.

The Solution

Just comment out StringLength and use the Range Attribute.

The Problem

You are trying to configure Widlcard routing (i.e. something like http://domain.com/SomeUserName/) and find it problematic.

The Cause

That is largely by design – wildcard routing is resource intensive and rarely needed.

The Solution

If you want to do it anyway, use the following routes

routes.MapRoute(“Default”, “”, new { controller = “Home”, action = “Index”, id = UrlParameter.Optional });
routes.MapRoute(“CatchAll”, “{*id}”, new { controller = “Home”, action = “Handle”, id = “” });

Things to note

• The Catch-All route is AFTER the home route
• The syntax is *id – this will ensure that the value of ID is sent to the “Handle” action
• The purpose of this route is to throw control to the “Handle” action with the appropriate value – Handle must be set up to use that value.

Okay, after some more digging (and some failed integration tests) here is what you have to do

Add in the following routes

routes.MapRoute(“Handle”, “Home/Handle/{id}”, new { controller = “Home”, action = “Handle”, id = “” });
routes.MapRoute(“User”, “{*id}”, new { controller = “Home”, action = “Index”, id = “” });
routes.MapRoute(“Default”, “{controller}/{action}/{id}”, new { controller = “Home”, action = “Index”, id = UrlParameter.Optional });

And then create an action called “Handler”, and change your Index action on your home controller to look like this

public ActionResult Index(string id=””)
{
if (!string.IsNullOrWhiteSpace(id))
{
return RedirectToAction(“Handle”, new {@id = id});
}
else {
return View();
}

What does this do?  It routes all wildcard traffic to your Index controller, which then hands it off to the “Handle” Action.  You would think that you could just hand everything off to the Handle action, but if you do that, then your Index action becomes inaccessible,  and in some circumstances you get a recursive loop where the handle action is called endlessly.  That does show an interesting error screen though.

One annoying side effect of this course of action is the need to map out each and every route explicitly, otherwise the wildcard route will pick it up and hand it off to the “Handle” action, which will take it somewhere where you do not want it to go.

The Problem

You are using the new JavaScript bundling and minification features in asp.net mvc 4, and some of your JavaScript files are not being included

The Cause

The minification process – in it’s strange wisdom, does not include .min files when it bundles.  Therefore something like

.Include(“~/Scripts/jHtmlArea-0.7.0.min.js”)

will not be included, leading to JavaScript errors.

The Solution

Just use the non-minified version of the script file –

.Include(“~/Scripts/jHtmlArea-0.7.0.js”)

will work just fine – it seems that the asp.net mvc bundler prefers to do it’s own minification.

The Problem

You are coding away, Visual Studio locks up for one of it’s many reasons, and reopen your project and run it again. You then get the “Unable to launch the visual studio development server because port 9452 is in use” error

The Cause

When Visual Studio crashed, the Web Server did not, so basically it thinks you are trying to run two instances at the same time, which is not allowed.

The Solution

Open up the process manager, go to the Processes tab, and select “WebDev.WebServer40.exe” and click “End Process”. Then try running your project again. Visual Studio will now start the project fresh and the problem should go away.

The Problem

You’re using the otherwise awesome ASP.net MVC 4 and you can use an ajax function once, via the @Ajax.ActionLink tool, but you try it again, and it does nothing.

The Cause

For whatever reason the browser thinks it is a cache page and pulls it from the cache – I’m not 100% sure of this.

The Solution

Just add a DateTime.Now as a parameter, this forces the browser to send the data every time.