How to pass validation errors from web api layer to MVC layer?

Question

I have a ASP.NET MVC application that makes calls to my ASP.NET Web API layer.

The Web API layer also uses EF 6.x (latest).

Now when e.g. say the MVC has a user form to create a new user, when the user hits submit I do:

1. The form is backed by my UserDTO
2. Pass the UserDTO as a parameter to my SaveUser web-api client.

Now in the Web API layer, if there is a validation error, how can I use attribute based validation and pass the error back to the MVC view page?

Update

I want to use ModelState.IsValid and if there are errors pass those back to the MVC layer.

Answer 1

create a error property in your UserDTO then return

public UserDTO saveuser(UserDTO user)
    if(validation error)
    {
    UserDto user = new UserDTO()
    User.error = [your error message]
    return user;
    }
else{
//////// save it and retuen null.
}

in your MVC

UserDTO user = saveuser();[your web api client]

then you handle it in the MVC.