Check if user exists in MVC4

Question

I have simple login form without registration, because I create Admin login, who create new users. So admin login, and create new user, which can then login with that specific username and password.

So I create this controller:

    public ActionResult CreateNew(Models.Users user)
    {

        if (ModelState.IsValid)
        {
            try
            {
                using (var dataU = new userDbEntities())
                {
                    var crypto = new SimpleCrypto.PBKDF2();
                    var encrpPass = crypto.Compute(user.Password);
                    var sysUser = dataU.UsersTables.Create();

                    sysUser.username = user.Username;
                    sysUser.password = encrpPass;
                    sysUser.passwordSalt = crypto.Salt;
                    sysUser.TimeZoneId = user.TimeZoneName;
                    sysUser.Customer = user.Customer;

                    dataU.UsersTables.Add(sysUser);
                    dataU.SaveChanges();
                    return RedirectToAction("Registration", "LoginAdmin");
                }
            }
            catch (Exception ex)
            {
                string error = ex.Message;
            }

        }

        return View(user);
    }

Problem is, that I can create users with same username (this is not ok!), so how to check if user with that name exists and returns, this username already exists...

thanks...

Answer 1

count the number of user that has the same username and add the user if the count is 0.

for example

var count = dataU.UsersTables.Count(u=>u.UserName == usernameyouwanttocheck);
if(count==0)
{
  //add user
}
else
{
  //alert user saying user exists
}

if I were you I would make repository and create a function that checks if the user exists or not and call that function from controller.

Answer 2

By help of Biplov13 I create this, which is working:

public ActionResult CreateNew(Models.Users user)
        {

            if (ModelState.IsValid)
            {
                try
                {
                    using (var dataU = new userDbEntities())
                    {

                        {
                            var crypto = new SimpleCrypto.PBKDF2();
                            var encrpPass = crypto.Compute(user.Password);
                            var sysUser = dataU.UsersTables.Create();

                            sysUser.username = user.Username;
                            sysUser.password = encrpPass;
                            sysUser.passwordSalt = crypto.Salt;
                            sysUser.TimeZoneId = user.TimeZoneName;
                            sysUser.Customer = user.Customer;

                            var count = dataU.UsersTables.Count(u => u.username == user.Username);
                            if (count == 0)
                            {
                                dataU.UsersTables.Add(sysUser);
                                dataU.SaveChanges();
                                return RedirectToAction("Registracija", "LoginAdmin");
                            }
                            else
                            {
                                // something to do if user exist...
                            }


                        }

                    }
                }
                catch (Exception ex)
                {
                    string error = ex.Message;
                }

            }

            return View(user);
        }