Is it possible to toggle Validation Data Annotations on/off in MVC 3?

Question

I have two separate VIEWS accessing the same MODEL. When I put the validator data annotations on the model, it works as advertised and prevents the data from being submitte

Answer 1

I solved this problem using a different approach.

The trick is not to disable validation per-se, but to clear any inappropriate validation errors before the controller's action is invoked (so ModelState.IsValid returns true).

If a Model (or ViewModel) object requires custom validation then it implements an interface I defined called ICustomValidation which looks like this:

public interface ICustomValidation {
    void PerformValidation(ModelStateDictionary modelState);
}

My BaseController class (which all of my controllers subclass) has this method override:

protected override void OnActionExecuting(ActionExecutingContext filterContext) {
    base.OnActionExecuting(filterContext);

    // Unfortunately it seems this is the only way to get the Model object
    if( filterContext.ActionParameters.ContainsKey("model") ) {

        Object                    model = filterContext.ActionParameters["model"];
        ModelStateDictionary modelState = filterContext.Controller.ViewData.ModelState; // ViewData.Model always returns null at this point.

        ICustomValidation modelValidation = model as ICustomValidation;
        if( modelValidation != null ) {
            modelValidation.PerformValidation( modelState );
        }
    }

}

So in an example ViewModel class, if I want to disable (or rather: disregard) certain validation errors then it just needs to do this:

public class SomeModel : ICustomValidation {

    [Required]
    public Boolean NamePresent { get; set; }

    [Required]
    public String Name { get; set; }

    public void PerformValidation(ModelStateDictionary modelState) {
        if( !NamePresent ) dict.Remove("Name");
    }
}

In my actual code there's a bit more logic that clears the ModelStateDictionary in a model-recursive and by-prefix method which keeps it robust.

My solution does not match your problem exactly, but using a similar approach you should be able to get it to work for you.