Localizing/Overriding ASP.NET Identity 3 Error Messages in ASP.NET Core

Saturday, July 11, 2015

Introduction:

If you ever develop an app with modern ASP.NET Identity framework then you know that at specific condition ASP.NET Identity returns some specific errors. For example, if email is invalid then framework will return Email 'x@y.com' is invalid message. These error messages are great but what if you want to override these error message. For example, if you are developing multi-lingual site then these error messages does not make any sense. ASP.NET Identity 3 makes it very easy to override/localize these identity error messages. There was no easy way to override these messages in ASP.NET Identity 2.x.x. In-fact 2 years ago, I opened an issue at codeplex. The issue was closed and then re-opened because the team now is planning to port this functionality form version 3 to version 2. In this post, I will show you how we can override these error messages in ASP.NET Identity 3.

Description:

Note that I am using beta5 at the time of writing. We just need add a class inheriting from IdentityErrorDescriber class,

001public class MyIdentityErrorDescriber : IdentityErrorDescriber
002{
003    public MyIdentityErrorDescriber()
004    {
005    }
006 
007    public override IdentityError ConcurrencyFailure()
008    {
009        //return new IdentityError
010        //{
011        //    Code = nameof(ConcurrencyFailure),
012        //    Description = Resources.ConcurrencyFailure
013        //};
014        return base.ConcurrencyFailure();
015    }
016 
017    public override IdentityError DefaultError()
018    {
019        return base.DefaultError();
020    }
021 
022    public override IdentityError DuplicateEmail(string email)
023    {
024        return base.DuplicateEmail(email);
025    }
026 
027    public override IdentityError DuplicateRoleName(string name)
028    {
029        return base.DuplicateRoleName(name);
030    }
031 
032    public override IdentityError DuplicateUserName(string name)
033    {
034        return base.DuplicateUserName(name);
035    }
036 
037    public override IdentityError InvalidEmail(string email)
038    {
039        return base.InvalidEmail(email);
040    }
041 
042    public override IdentityError InvalidRoleName(string name)
043    {
044        return base.InvalidRoleName(name);
045    }
046 
047    public override IdentityError InvalidToken()
048    {
049        return base.InvalidToken();
050    }
051 
052    public override IdentityError InvalidUserName(string name)
053    {
054        return base.InvalidUserName(name);
055    }
056 
057    public override IdentityError LoginAlreadyAssociated()
058    {
059        return base.LoginAlreadyAssociated();
060    }
061 
062    public override IdentityError PasswordMismatch()
063    {
064        return base.PasswordMismatch();
065    }
066 
067    public override IdentityError PasswordRequiresDigit()
068    {
069        return base.PasswordRequiresDigit();
070    }
071 
072    public override IdentityError PasswordRequiresLower()
073    {
074        return base.PasswordRequiresLower();
075    }
076 
077    public override IdentityError PasswordRequiresNonLetterAndDigit()
078    {
079        return base.PasswordRequiresNonLetterAndDigit();
080    }
081 
082    public override IdentityError PasswordRequiresUpper()
083    {
084        return base.PasswordRequiresUpper();
085    }
086 
087    public override IdentityError PasswordTooShort(int length)
088    {
089        return base.PasswordTooShort(length);
090    }
091 
092    public override IdentityError UserAlreadyHasPassword()
093    {
094        return base.UserAlreadyHasPassword();
095    }
096 
097    public override IdentityError UserAlreadyInRole(string role)
098    {
099        return base.UserAlreadyInRole(role);
100    }
101 
102    public override IdentityError UserLockoutNotEnabled()
103    {
104        return base.UserLockoutNotEnabled();
105    }
106 
107    public override IdentityError UserNotInRole(string role)
108    {
109        return base.UserNotInRole(role);
110    }
111}

For each error, we just need to return IdentityError object which include Code and Description properties. Code is a short-error-message and Description include the details of the error. In real world application, we can get the error-messages from resource files. Currently, there is very little support of localization(including ASP.NET Core application cannot add resx file from Visual Studio). But its coming. Now we just need to register this class in Startup.ConfigureServices method,

`1`	`services.AddTransient<IdentityErrorDescriber, MyIdentityErrorDescriber>();`

Summary:

ASP.NET Identity 3 makes it very easy to override the internal error messages that framework returns during validation. In this article, I showed you how we can localize these error messages.

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