Question

I have a simple form which is using ASP.NET MVC 3 unobtrusive client side validation.

The model looks a bit like this (names changed for privacy):

public class MyInputModel
{
    public MyInputModel()
    {
    }

    public MyInputModel(MyViewData viewData)
    {
        ViewData = viewData;
        MaxValueForSize = viewData.MaxSize;
    }

    public int MaxValueForSize { get; set; }


    [RegularExpression("[1-9][0-9]*",ErrorMessage = "The value must be a whole number.")]
    public int Size { get; set; }

    [StringLength(255)]
    [Required]
    public string Description{ get; set; }
}

In my view I put a hidden field in for MaxValueForSize and I want to compare the entered value for Size to less than or equal to the MaxValueForSize property.

I know I can do this server side by overriding validation attribute like so:

internal class SizeValidAttribute : ValidationAttribute
{
    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
        if(value != null)
        {
            var model = (MyInputModel) validationContext.ObjectInstance;


            if ((int)value > model.MaxValueForSize)
                return new ValidationResult(ErrorMessage);

        }
        return base.IsValid(value, validationContext);
    }
}

However I would like to (need to) have client side validation on this property. Similar to how the Compare annotation works.

Does anyone know of a way to do this? Do I need to extend the client side validation somehow?

Thanks for your help.

Answer 1

Have a look at this article. It explains how to extend the ASP.NET MVC model validation to support cross-field validation:

Extending ASP.NET MVC’s Validation
http://blogs.msdn.com/b/mikeormond/archive/2010/10/05/extending-asp-net-mvc-s-validation.aspx