为什么Automapper无法用于基类和继承的类

Question

In an MVC application, there is a Student class inherited from ApplicationUser base class (ASP.NET Identity) and there is a ViewModel of it called StudentViewModel as shown below:

Entity Classes:

public class ApplicationUser : IdentityUser<int, ApplicationUserLogin,
                                     ApplicationUserRole, ApplicationUserClaim>, IUser<int>
{
    public string Name { get; set; }
    public string Surname { get; set; } 
    //code omitted for brevity
}

public class Student: ApplicationUser
{     
    public int? Number { get; set; }
}

ViewModel:

public class StudentViewModel
{
    public int Id { get; set; }     
    public int? Number { get; set; }
    //code omitted for brevity
}

I use the following method in order to update a Student by mapping StudentViewModel to ApplicationUser in the Controller:

[HttpPost]
[ValidateAntiForgeryToken]
public JsonResult Update([Bind(Exclude = null)] StudentViewModel model)
{
    //Mapping StudentViewModel to ApplicationUser ::::::::::::::::
    var student = (Object)null;

    Mapper.Initialize(cfg =>
    {
        cfg.CreateMap<StudentViewModel, Student>()
            .ForMember(dest => dest.Id, opt => opt.Ignore())
            .ForAllOtherMembers(opts => opts.Ignore());
    });

    Mapper.AssertConfigurationIsValid();
    student = Mapper.Map<Student>(model);
    //::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

    //Then I want to pass the mapped property to the UserManager's Update method:
    var result = UserManager.Update(student);

    //code omitted for brevity              
}

When using this method, I encounter an error:

The type arguments for method 'UserManagerExtensions.Update(UserManager, TUser)' cannot be inferred from the usage. Try specifying the type arguments explicitly.

Any idea to fix it?

Answer 1

The error you are getting has nothing to do with AutoMapper .

The problem is that your student variable is of type object due to the following line

var student = (Object)null;

while it should be Student .

Either remove the above line and use

var student = Mapper.Map<Student>(model);

or change it to

Student student = null;