javascript - Custom ValidationAttribute not displaying error -

i wrote custom validationattribute check if email exists in db. error message not displayed, , validation occurs after submit form. html contains reference javascript files display messages still no result. nevertheless other attributes work fine , respective message displayed.

public class noduplicateemail : validationattribute {         protected override validationresult isvalid(object value, validationcontext validationcontext)      {           var context = new mhotivocontext();           var email = validationcontext.objectinstance.gettype().getproperties(              ).firstordefault(prop => isdefined(prop, typeof(noduplicateemail)));           var emailvalue = (string)email.getvalue(validationcontext.objectinstance);           if(context.users.firstordefault(x => x.email == emailvalue)!=null)              return new validationresult("email in use!");           return validationresult.success;       }   } 

    [required(errormessage = "email required")]     [datatype(datatype.emailaddress)]     [display(name = "email")]     [noduplicateemail] 

the object value parameter of isvalid method contains value of email property var email , var emailvalue lines of code unnecessary. code should be

public class noduplicateemail : validationattribute {   private const string _defaulterrormessage = "email {0} in use!"   public noduplicateemail() : : base(_defaulterrormessage)   {   }    protected override validationresult isvalid(object value, validationcontext validationcontext)   {     var context = new mhotivocontext();     if (value != null)     {       var email = (string)value;       if(context.users.firstordefault(x => x.email == emailvalue) != null)       {         return new validationresult(formaterrormessage(email));       }     }     return validationresult.success;   } } 

however should not accessing database resources in validation attribute (that not responsibility , code impossible unit test). should using [remote] attribute client side validation , calling service server side validation.

instead create service method returns value indicating valid (or add private method in controller

private bool isemailinuse(string email) {   return context.users.any(x => x.email == email) } 

and actionresult client side validation

public jsonresult isuniqueemail(string email) // parameter name must match property name {   bool isinuse = isemailinuse(email);   return json(!isinuse, jsonrequestbehavior); } 

and apply remoteattribute property

[remote("isuniqueemail", yourcontrollername, errormessage = "the email in use")] public string email { get; set; } 

and finally, in post method (in case of malicious user, or javascript has been disabled)

public actionresult yourmethod (yourmodel model) {   if (isemailinuse(model.email)   {     // add modelstate error , return view   }  } 

or catch exception when save (assuming data base field has unique constraint)