Removing a user from backend created by IdentityServer4 - asp.net-core

Question

I am debugging confirmation email flow when signing up a new User in Asp.Net Core web application with Identity Server 4.
Since I had already signed up with my actual email, to reuse it, I modified the UserName and Email in AspNetUsers table using SQL Update to some random value.
Now when I am signing up with the original email again. I am getting a duplicate user error
result = await _userManager.CreateAsync(user, model.Password);
I have already:
Cleared browser cache.
Closed local IIS Express
Restarted Visual Studio.
Used_userManager.DeleteAsync() after updating the UserName and Email back to original values but this gives an Microsoft.AspNetCore.Identity.IdentityError with description Optimistic concurrency failure, object has been modified.
On running this query on Sql Server
select * from INFORMATION_SCHEMA.COLUMNS where COLUMN_NAME in ( 'UserName' , 'Email')
I get the following:
I know that this is not a good practice to mess with backend, but this is development environment and I could continue my work with another email.
I would request readers to help in understanding how the User could be safely scorched to be able to reuse the email.
Appreciate your time

Answer 1

I agree with Kyle's comment and to further speed up your debug process you should note that if you use gmail to do this you can debug this process using one email.
from google/gmails perspective myaccount#gmail.com == my.acount#gmail.com == m.y.a.c.c.ount#gmail.com etc etc just try it out, google disregards all period characters in the email. you can enumerate/exhaust ~2^8 emails (in this example) if you just enumerate through the local-part of the e-mail address. but from your applications side, myaccount#gmail.com is not the same as my.account#gmail.com, ie they are different user accounts. Basically you can use one email to test out this feature of yours without having to delete the user.

Answer 2

Here is how I did it and finally got passed the pesky "concurrency failure" error message... This works in ASP.NET CORE 2.2
Obtain the user object through the FindByName method first.
Remove the user from their assigned Role (in this case I hard coded "Admin" because that is the role I'm interested in but fill in your own), then delete the user.
//Delete user.
//Obtain the user object through the FindByName method first.
//Remove the user from their assigned Role, then delete the user.
var userManager = serviceProvider.GetRequiredService<UserManager<ApplicationUser>>();
ApplicationUser delAppUser = new ApplicationUser
{
Email = "SomeEmailForindividualAdminUser",
UserName = "SomeUsernameindividualAdminUser"
};
Task <ApplicationUser> taskGetUserAppUser = userManager.FindByNameAsync(delAppUser.UserName);
taskGetUserAppUser.Wait();
Task<IdentityResult> taskRemoveFromRoleAppUser = userManager.RemoveFromRoleAsync(taskGetUserAppUser.Result, "Admin");
taskRemoveFromRoleAppUser.Wait();
Task<IdentityResult> taskDeleteAppUser = userManager.DeleteAsync(taskGetUserAppUser.Result);
taskDeleteAppUser.Wait();