Identity - Custom User Validators

Question

Helloes,

I have a .NetCore MVC APP with Identity and using this guide I was able to create custom user validators.

public class UserDomainValidator&l         


        

Answer 1

Answer for those who just want to extend existing default user validation, without the risk of breaking something.

You can use the Decorator pattern and instead of copying/changing default UserValidator you can just perform additional validation of the user data. Here is an example:

public class UserValidatorDecorator : IUserValidator where TUser : ApplicationUser
{
    // Default UserValidator
    private readonly UserValidator _userValidator;
    // Some class with additional options
    private readonly AdditionalOptions _additionalOptions;
    // You can use default error describer or create your own
    private readonly IdentityErrorDescriber _errorDescriber;

    public UserValidatorDecorator(UserValidator userValidator,
                                  AdditionalOptions additionalOptions,
                                  IdentityErrorDescriber errorDescriber)
    {
        _userValidator = userValidator;
        _additionalOptions = additionalOptions;
        _errorDescriber = errorDescriber;
    }

    public async Task ValidateAsync(UserManager manager,
                                                    TUser user)
    {
        // call to default validator
        var identityResult = await _userValidator.ValidateAsync(manager, user);

        // if default validation is already failed you can just return result, otherwise call  
        // your additional validation method
        return identityResult.Succeeded ? 
            AdditionalValidation(user) :
            identityResult;
    }

    public IdentityResult AdditionalUserNameValidation(TUser user)
    {
        // now you can check any value, if you need you can pass to method 
        // UserManager as well
        var someValue = user.SomeValue;

        if (someValue < _additionalOptions.MaximumValue)
        {
            return IdentityResult.Failed(_errorDescriber.SomeError(userName));
        }

        return IdentityResult.Success;
    }
}

And then you need to register your decorator, it depends on version of .NET framework, I use such code for .NET Core 3.0:

// First register default UserValidator and your options class
services.AddScoped>();
services.AddScoped();
// Then register Asp Identity and your decorator class by using AddUserValidator method
services.AddIdentity()
    .AddEntityFrameworkStores()
    .AddUserValidator>();