Create a folder DTOs

In DTOs create a new class UserForRegistration with two props:

  • string Username
  • string Password

This object will be created as a target for the deserialization of the JSON sent to the Register action.


In Controllers create a new class AuthController derived from Controller.

Add a constructor with a parameter for DI

private readonly IAuthRepository _repo;

public AuthController(IAuthRepository repo)
    _repo = repo;

Add a new action to handle a new user registration

public async Task<IActionResult> Register([FromBody] UserForRegistration userForRegistration)
    // TODO validation

    // Convert username to lowercase to avoid multiple user with similar names like "John" and "john"
    // Use invariant to avoid conflicts for users from different cultures
    userForRegistration.Username = userForRegistration.Username.ToLowerInvariant();

    if(await _repo.UserExists(userForRegistration.Username)){
        return BadRequest("Username already in use");

    var userToCreate = new Models.User{ Username = userForRegistration.Username };
    var createdUser = await _repo.Register(userToCreate, userForRegistration.Password);

    // TODO this 201 is just a temporary solution, we should return a path to the new entity
    return StatusCode(201);

Testing with Postman

In Postman create a new folder Auth inside our colleection and add a new request.

Change the type to POST and set the url to https://localhost:5001/api/auth/register.

Switch to the Body tab, change to raw and select JSON from the drop down.

Add a payload to the body:

	"Username": "John",
	"Password": "password"

In vscode activate the debug pane, from the top bar of the pane change to .Net Core Attach, then press the start button. In the new popup select the dotnet exec for the DatingApp.API, be sure your do not select the dotnet watch process.

Add a breakpoint in the Register action.

Send the request from Postman. The request for the Username “John” will hit the breakpoint, step to see what is happening until Postman receives a 201 Created.

If we send the same request a second time and we follow it using the debugger then the UserExists method finds a user already registered with that name and returns. Postman receives a 400 Bad Request with a response body containing Username already in use.