Question

If two of textboxes fail validation at once then the ValidationSummary displays the same message twice.

Am I doing something wrong? Or is there a setting I can change to hide duplicate messages?

 

I have broken it down to the simplest example:

View:

@model MyModel
@Html.ValidationSummary()
@Html.TextBoxFor(model => model.A)
@Html.TextBoxFor(model => model.B)

Model:

public class MyModel : IValidatableObject
{
    public int A { get; set; }
    public int B { get; set; }

    public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
    {
        //Some logic goes here.        
        yield return new ValidationResult("Validation failed", new[] { "A", "B" });
    }
}

Result:

Answer 1

They are not duplicate from the point of view of ValidationSummary – you are assigning model state error to both fields A and B, so there must be 2 errors in validation summary. It doesnt “know” that they are the same.

Easy solutions :

• assign model only to one of them
• exclude property-assigned errors from summary – Html.ValidationSummary(true)

A little bit harder solution :

• make your own ValidationSummary helper, call standard validation summary logic in it, and then filter the result in “select distinct” way (linq is your friend here).

EDIT:

something like this for example :

public static class ValidationExtensions
{
    public static MvcHtmlString FilteredValidationSummary(this HtmlHelper html)
    {
        // do some filtering on html.ViewData.ModelState 
        return System.Web.Mvc.Html.ValidationExtensions.ValidationSummary(html);
    }
}