.net mvc 2 validation: summing up values of several attributes

Question

I am using .NET 4 MVC 2 in my project. I basically have two classes, which I use for my validation. Class A is my (main) model, class B is an composite attribute which class A may have. The code looks like the following:

[Bind(Exclude = "A_ID")]
    public class A_Validation
    {
        [Required(ErrorMessage = "something is missing")]
        public string title { get; set; }

        // some more attributes ...

        public B b { get; set; }
    }

All my validation based on class A is working very well. But now I want to validate the composite attribute B, which looks like the following.

[Bind(Exclude = "B_ID")]
    public class B_Validation
    {
        [Required(ErrorMessage = "missing")]
        [Range(1, 210, ErrorMessage = "range between 1 and 210")]
        public int first { get; set; }

        [Required(ErrorMessage = "missing")]
        [Range(1, 210, ErrorMessage = "range between 1 and 210")]
        public int second { get; set; }

        [Required(ErrorMessage = "missing")]
        [Range(1, 210, ErrorMessage = "range between 1 and 210")]
        public int third { get; set; }
    }

I am able to check the ranges of B's three attributes first,second and third. What I additionally want is to check if the sum of all three attributes first,second and third is below a certain threshold.

Any ideas how to proceed?

I think ViewModels might help, but i have no experience in using them.

Darin Dimitrov · Accepted Answer · 2011-06-26 16:55:37Z

0

Have you tried writing a custom validation attribute:

public class SumBelowAttribute : ValidationAttribute
{
    private readonly int _max;
    public SumBelowAttribute(int max)
    {
        _max = max;
    }

    public override bool IsValid(object value)
    {
        var b = value as B_Validation;
        if (b != null)
        {
            return b.first + b.second + b.third < _max;
        }
        return base.IsValid(value);
    }
}

and then decorate the B property with this attribute:

[SumBelow(123)]
public B b { get; set; }

answered Jun 26, 2011 at 16:55

Darin Dimitrov

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7 Comments

Jaques le Fraque Over a year ago

@Darin I've done this, but how should the view be able to show this validation result? first, second and third are all attributes which I can validate by using <%: Html.ValidationMessageFor(model => model.B.first)%> - how should I proceed with the sum?

Darin Dimitrov Over a year ago

@Jaques le Fraque, because this attribute applies to many properties you no longer use ValidationMessageFor to display error messages. You could display it using the ValidationSummary helper.

Jaques le Fraque Over a year ago

@Darin Dimitrov, the ErrorMessage I provided via [SumBelow(123, ErrorMessage = "sum below 123")] isn't shown in the ValidationSummary. Anyway, I also tried adding a clientside validation, which is not triggered at all

Darin Dimitrov Over a year ago

@Jaques le Fraque, have you tried like this @Html.ValidationSummary(false)? As far as client side validation is concerned this you will need to write a custom adapter for the jquery validate plugin.

Jaques le Fraque Over a year ago

@Darin Dimitrov, yes, I did the exact thing but this validation result is still missing :/

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