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.

Answer 2

This isn't possible via the default set of data annotations.. however, you have the choice of using 2 separate view models or writing your own validationAttribute.

I wrote this once.. although I loathed using it..

public class RequiredOnAttribute : ValidationAttribute
{
    public string[] URLs { get; set; }

    public override bool IsValid(object value)
    {
        if (URLs.Contains(System.Web.HttpContext.Current.Request.Url.AbsolutePath))
        {
            if (string.IsNullOrEmpty(value as string))
            {
                return false;
            }
        }
        return true;
    }
}

Usage:

[RequiredOn(URLs = new string[] { "/create", "/edit" })]
public string MyModelField { get; set; }

You could do the same for Range, RegEx, etc..

Answer 3

I too would suggest using a different view model object. This article has a nice example of how to implement it cleanly http://lostechies.com/jimmybogard/2009/06/30/how-we-do-mvc-view-models/

Alternatively, you could simply not call ModelState.IsValid on the controller.