Inheritance in C#: changing the return type - how to fix the error?

Question

OOP

abstract class ALauncher
   {
       protected abstract Object parseArgs(string[] args);
   }

   class Launcher : ALauncher
   {
       protected override ABitFileManager parseArgs(string[] args) {...}
   }

Why does the inheritance error occur? After all, ABitFileManager is an inheritor of Object (like any other class)?

Answer 1

C# does not support return type covariance.

Answer 2

Generalizations can probably help you.

interface ILauncher
  {
    object ParseArgs(string[] args);
  }

  abstract class ALanucher<T> : ILauncher
  {
    protected abstract T ParseArgs(string[] args);

    object ILanucher.ParseArgs(string[] args)
    {
      return ParseArgs(args);
    }
  }

  class Launcher : ALanucher<int>
  {
    protected override int ParseArgs(string[] args)
    {
      throw new NotImplementedException();
    }
  }