MVC: Override default ValidationMessage

user_192999 0
Viewed 19166

In the world of MVC I have this view model...

public class MyViewModel{

[Required]
public string FirstName{ get; set; }    }

...and this sort of thing in my view...

<%= Html.ValidationSummary("Please correct the errors and try again.") %>
<%= Html.TextBox("FirstName") %>
<%= Html.ValidationMessage("FirstName", "*") %>

My question: If I submit this form without supplying a name, I get the following message "The FirstName field is required"

OK. So, I go and change my property to...

[DisplayName("First Name")]
[Required]
public string FirstName{ get; set; }

..and now get "The First Name field is required"

All good so far.

So now I want the error message to display "First Name Blah Blah". How can I override the default message to display DisplayName + " Blah Blah", wihtout annotating all the properties with something like 

[Required(ErrorMessage = "First Name Blah Blah")]

Cheers,

ETFairfax

data-annotations html-helper asp.net-mvc
8 Answers
public class GenericRequired: RequiredAttribute
{
    public GenericRequired()
    {
        this.ErrorMessage = "{0} Blah blah"; 
    }
}
ckarbass_677190

It seems that RequiredAttribute doesn't implement IClientValidatable, so if you override the RequiredAttribute it breaks client side validation.

So this is what I did and it works. Hope this helps someone.

public class CustomRequiredAttribute : RequiredAttribute, IClientValidatable
{
    public CustomRequiredAttribute()
    {
        this.ErrorMessage = "whatever your error message is";
    }

    public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context)
    {
        yield return new ModelClientValidationRule
        {
            ErrorMessage = this.ErrorMessage,
            ValidationType = "required"
        };
    }
}
user_971540

This worked for me. Carefully read the comments inside the code. (Based on Chad's answer).

 // Keep the name the same as the original, it helps trigger the original javascript 
 // function for client side validation.

        public class RequiredAttribute : System.ComponentModel.DataAnnotations.RequiredAttribute, IClientValidatable
            {
                public RequiredAttribute()
                {
                    this.ErrorMessage = "Message" // doesnt get called again. only once.
                }

                public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context)
                {
                    yield return new ModelClientValidationRule
                    {
                        ErrorMessage = "Message", // this gets called on every request, so it's contents can be dynamic.
                        ValidationType = "required"
                    };
                }
            }
user_2740780
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