Microsoft.AspNetCore.Identity.UserManager – User creation failed

The Microsoft.AspNetCore.Identity.UserManager – User creation failed error typically occurs when there is a problem during the user creation process in ASP.NET Core Identity. This error can be caused by a variety of reasons related to user validation, password policies, or database constraints.

Common Causes of “User creation failed” Error:

1. Invalid User Properties:
   • If the user properties (like username, email, etc.) don’t meet the validation criteria, the user creation will fail. For example, if the username already exists, or the email is invalid, it can lead to this error.
2. Password Validation Issues:
   • ASP.NET Core Identity may have specific password requirements (length, complexity, etc.). If the password does not meet the defined policy, the user creation will fail.
3. Unique Constraints Violation:
   • If the database has constraints like unique indexes on fields (e.g., email, username), user creation may fail if there is an attempt to create a user with a duplicate value in those fields.
4. Role Assignment Issues:
   • If you’re trying to assign roles to the user during creation, and those roles don’t exist or there are issues with the roles, it may cause user creation to fail.
5. Database Connection or Migration Issues:
   • If there are issues with the database connection or if the database schema is out of sync (e.g., missing required tables or fields), the user creation process may fail.
6. Custom UserManager or Validator Logic:
   • If you have custom validation logic or overrides in the UserManager, any exceptions or failures in that logic can cause user creation to fail.

Steps to Diagnose and Fix:

1. Check UserManager Results:

The UserManager.CreateAsync() method returns a result object that contains information about why the user creation failed. You can examine the IdentityResult returned to determine the specific cause of the failure.

Example of handling user creation errors:

var result = await userManager.CreateAsync(user, password);

if (!result.Succeeded)
{
    foreach (var error in result.Errors)
    {
        // Log or handle specific errors
        Console.WriteLine($"Error: {error.Description}");
    }
}
else
{
    // User creation succeeded
}

The result.Errors property will give you details about the reason for the failure, such as invalid email, weak password, or duplicate username.

2. Verify Password Requirements:

Ensure that the password meets the password policy defined in PasswordOptions in the IdentityOptions. These settings are usually configured in Startup.cs or Program.cs.

Example of setting password requirements:

services.Configure<IdentityOptions>(options =>
{
    options.Password.RequireDigit = true;
    options.Password.RequiredLength = 6;
    options.Password.RequireNonAlphanumeric = false;
    options.Password.RequireUppercase = true;
    options.Password.RequireLowercase = true;
    options.Password.RequiredUniqueChars = 1;
});

If the password doesn’t meet these requirements, the CreateAsync() method will fail.

3. Check for Duplicate User (Email/Username):

If the email or username is already taken, user creation will fail. You should check for existing users before attempting to create a new one.

Example of checking for existing user:

var existingUser = await userManager.FindByEmailAsync(user.Email);
if (existingUser != null)
{
    // Handle email already taken error
}

4. Validate Roles:

If you’re assigning roles during user creation, ensure the roles exist in the database before attempting to assign them. You can use RoleManager to check if the role exists.

Example of checking roles:

var roleExists = await roleManager.RoleExistsAsync("Admin");
if (!roleExists)
{
    // Create role if it doesn't exist
    var role = new IdentityRole("Admin");
    await roleManager.CreateAsync(role);
}

5. Database Schema and Connection:

Ensure that the database schema is up to date and that the AspNetUsers table (or custom user table) is correctly set up. You may need to run migrations to update the database schema.

Run migrations:

dotnet ef migrations add CreateIdentitySchema
dotnet ef database update

6. Check for Custom Validation:

If you have custom validation logic implemented (e.g., via IUserValidator<TUser> or IPasswordValidator<TUser>), check if the validation logic is causing the failure.

Example of a custom user validator:

public class CustomUserValidator : IUserValidator<ApplicationUser>
{
    public Task<IdentityResult> ValidateAsync(UserManager<ApplicationUser> manager, ApplicationUser user)
    {
        var errors = new List<IdentityError>();

        if (user.UserName.Contains("test"))
        {
            errors.Add(new IdentityError
            {
                Description = "Username cannot contain 'test'."
            });
        }

        return Task.FromResult(errors.Count == 0 ? IdentityResult.Success : IdentityResult.Failed(errors.ToArray()));
    }
}

7. Examine IdentityError Messages:

When CreateAsync() fails, the error messages provided in the IdentityResult.Errors can help diagnose the specific issue. Common errors include:

• Invalid email (format issues or email already taken).
• Password issues (too short, lacks required characters, etc.).
• User already exists (duplicate username or email).

Example of Creating a User:

Here’s an example of how to create a user and handle potential errors:

public async Task<IActionResult> CreateUserAsync(string email, string password)
{
    var user = new ApplicationUser { UserName = email, Email = email };
    var result = await userManager.CreateAsync(user, password);

    if (!result.Succeeded)
    {
        foreach (var error in result.Errors)
        {
            ModelState.AddModelError("", error.Description); // Add errors to ModelState for display
        }
        return View();
    }

    // Optionally assign roles
    await userManager.AddToRoleAsync(user, "User");

    return RedirectToAction("Index", "Home"); // Redirect to a different page
}