identity.cs

var userStore = new UserStore<IdentityUser>();
var manager = new UserManager<IdentityUser>(userStore);

var user = new IdentityUser() { UserName = UserName.Text };
IdentityResult result = manager.Create(user, Password.Text);

if (result.Succeeded)
{
    StatusMessage.Text = string.Format("User {0} was created successfully!", user.UserName);
}
else
{
    StatusMessage.Text = result.Errors.FirstOrDefault();
}