How does validation in ASP.NET MVC 2 actually work?

Question

I am trying to trace through why my ASP.NET MVC 2 validation isn't working, but I cant find enough about HOW it works to be able to do this.

I have followed the steps in this useful article by David Hayden which seems to be the best documentation currently out there, but nothing actually happens.

I get validation when i submit to the server (as I did since Preview 1 when i added data annotations to my model) but I'm not getting any client side validation.

How can i trace through to test? So far I have verified the following obvious things

• MicrosoftMvcJQueryValidation.js and jquery.validate.min.js files are being downloaded
• Html.ClientValidationEnabled = true

I cant see easily what is hooking up to which events to know quite how to debug it.

Answer 1

Here's what I've learnt:

MOST IMPORTANT

• Your HTML Form must be created with the using directive, not just BeginForm and EndForm.
• You must set Html.ClientValidationEnabled = true BEFORE you start your 'Form'
• You must use Html.ValidationMessage for each field
• You must set Html.ClientValidationEnabled = true on each partial control (ascx)

HOW IT WORKS (very simple overview)

• When you do Html.BeginForm it creates a 'FormContext' in the ViewContext
• When ValidationMessage helpers are used, metadata is put into the form context
• When the form is disposed (by the using statement) it writes out all the validation code

MISC

• I cannot seem to get validation working when I have a partial control, if that control uses a different model from the view that defines the Form.

• You do NOT need to use Html.TextBoxFor or Html.ValidationMessageFor, you can use Html.TextBox and Html.ValidationMessage