How can I implement custom validation in ASP.NET Core Identity?

How can I implement custom validation in ASP.NET Core Identity?

You can implement custom validation by creating a custom validator class that inherits from IValidator. This allows you to define your own validation logic.

Can you show me an example of a custom validator?

Sure! Here's a simple example:

public class CustomUserValidator : IUserValidator<ApplicationUser>
{
    public Task<IdentityResult> ValidateAsync(UserManager<ApplicationUser> manager, ApplicationUser user)
    {
        var errors = new List<IdentityError>();
        if (user.UserName.Contains("@"))
        {
            errors.Add(new IdentityError { Description = "Username cannot contain '@' character." });
        }
        return Task.FromResult(errors.Any() ? IdentityResult.Failed(errors.ToArray()) : IdentityResult.Success);
    }
}

How do I register this custom validator in my application?

You can register your custom validator in the Startup.cs file within the ConfigureServices method like this:

services.AddIdentity<ApplicationUser, IdentityRole>()
    .AddEntityFrameworkStores<ApplicationDbContext>()
    .AddUserValidator<CustomUserValidator>();

What other types of custom validations can I implement?

You can implement validations for password strength, email format, or even custom business rules specific to your application.