A field initializer cannot reference the non-static field, method, or property in ASP.Net MVC Controller

Question

I have a BaseController class inherited from MVC Controller-

public abstract class BaseController : Controller
{
    protected int A= Convert.ToInt32(ConfigurationManager.AppSettings["A"]);
    protected int B= Convert.ToInt32(ConfigurationManager.AppSettings["B"]);

    protected int C= A* B;
}

It gives error A field initializer cannot reference the non-static field, method, or property during compile.

I don't have any constructor. And that's full code of this class. Any help?

Answer 1

The error message relates to your attempt to assign C the value of A * B.

Try creating a protected contructor that carries out the assignment operation, ensure your sub classes then call this base constructor.

Answer 2

Since BaseController is an abstract class, you cannot create an instance of the class. So, you cannot call constructor of the abstract class. But you have to have a constructor to run the following code.

protected int C= A* B;

So, only way to create a constructor of abstract or base class and call base constructor from derived class, as like follows.

public DerivedClass() : base() {
    // Do additional work here otherwise you can leave it empty
}

Answer 3

in short, the field initializers run before any constructor in the inheritance chain. So at that time the object is not yet constructed in this sense, so the non-static members cannot be used.

Check out this related many time quoted article

If these are some initial values, one solution would be to refactor the A*B assignment to use the configuration parameter directly.