This has been asked and answered numerous times, but I have a special situation where I have nullable integers in my model.
Model:
[Range(0, int.MaxValue, ErrorMessage = "Please enter valid integer number")]
public int? Jan { get; set; }
In my edit form, if enter "x", then the browser default error pop-up with "Please enter a number" appears. My own client-side validation doesn't appear to be kicking in. If I enter nothing, then it blows up server-side because a parameter was expected in my repository code.
I need it to validate non-integers on the client and I also need it to handle nulls, when someone tries to submit the form with an empty value. I cannot resort to a Required data annotation, because if I do, no data will be loaded. This is a conversion from legacy code to MVC.
UPDATE - CLARIFICATION:
I'm dealing with a lot of nullable ints. The decision to try and make them required was mine - am open to alternative options. I cannot change the int? in the model for various reasons. So, I need to validate against nulls on the client and server to ensure that integers are entered.
You can use the HTML5 required attribute client side to prevent empty values from being entered. If you really want to ensure no empty values are sent to the server, I believe you are going to need to do some server side validation as well.