I started to update an ASP.NET MVC 1.0 application to the new MVC 2.0 RC but will now put off that migration for now – I’ll wait for the RTM which should fix this.

The problem is to do with the FormCollection object throwing an ArgumentException (“Value cannot be null or empty”) when calling TryUpdateModel from within your controller:

at System.Web.Mvc.FormCollection.GetValue(String name) 
at System.Web.Mvc.DefaultModelBinder.BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext) 
at System.Web.Mvc.Controller.TryUpdateModel[TModel](TModel model, String prefix, String[] includeProperties, String[] excludeProperties, IValueProvider valueProvider) 
at System.Web.Mvc.Controller.TryUpdateModel[TModel](TModel model, IValueProvider valueProvider) 

This is apparently a known issue with the RC release and should be fixed in the next release. The project I am working on is fairly sizable and with the many uses of FormCollection, a lot of runtime errors have been created!

One suggested solution is to download the MVC source code and make a fix (hack?) to by-pass the issue. However, I’d rather stay on the main MVC branch and just wait for the RTM.

The issue surfaces when you try and invoke a button click on an input element of type “submit” through javascript. Simply use myButton.click()you say? Well, unfortunately no. It can be the case that the click appears to work in terms of invoking any other javascript that might be attached to that event, but it actually does not invoke the postback to the server. The button works perfectly when use the mouse, but just doesn’t work with the click() method.

So the solution is to fake the button being clicked with the mouse when in firefox, and otherwise to just use what you’d expect:

if (button.dispatchEvent)
{
var e = document.createEvent(“MouseEvents”);
e.initEvent(“click”, true, true);
button.dispatchEvent(e);
}
else
{
button.click();
}

Just the behaviour I wanted, except that when the post-back occurs from IE, the button’s event handler does not get triggered on the server!! Very strange … but this article on 4guysfromrolla.com gives a great explanation.

Basically, IE does not post-back a fully serialised form if there is only one textbox on the page! The server does not know what triggered the post-back and so cannot call the correct server-side event handler. The workaround? … add another textbox to the form (but just make it hidden!).

This is true for IE6 and IE7 …

Update 5 APR 2008: An example would be nice, so this is what I used…

<asp:TextBox ID=”IEPostbackBugFix” runat=”server” style=”visibility:hidden;display:none;” />