Is there runtime polymorphism in C# combined with generics?

Question

I have 2 classes that inherit from the same generic abstract class. Inheriting and implementing the methods with a type works fine, but I can't figure out how to do late binding with an instance of that abstract class.

 internal class NormalField : GenericClass<List<List<int>>>
    {
        protected override List<List<int>> doSomethingWithTheField(List<List<int>> field)
        {
            throw new NotImplementedException();
        }

        public override List<int> getFieldRow(int row)
        {
            throw new NotImplementedException();
        }
    }

internal class ComplexField : GenericClass<List<List<ComplexCell>>>
    {
        protected override List<List<ComplexCell>> doSomethingWithTheField(List<List<ComplexCell>> field)
        {
            throw new NotImplementedException();
        }

        public override List<int> getFieldRow(int row)
        {
            throw new NotImplementedException();
        }
    }

 public class ComplexCell
    {
        int field;
        int? secondField;
    }

public abstract class GenericClass<T>
    {
        public T Field;
        protected abstract T doSomethingWithTheField(T field); //class uses this internally 
        public abstract List<int> getFieldRow(int row); //used by another object
    }

Unfortunately I have to declare the type before compiling so I cant dynamically assign another instance of the abstract class to a property.

 public class Program
        {
            public static void Main(string[] args)
            {
               // I have to specify the type for the interface here and can't assign a complexfield later
               GenericClass instance = new NormalField(); //not possible
                instance =  new ComplexField();
                instance.getFieldRow(2);
            }
    
        }

A possible solution I came up with would be to seperate the getFieldRow() method from the abstract class and create a new interface with only the getFieldRow() method. Since there are no generics involved this would work, but is there also a way to do this with a abstract class with generics?

Answer 1

GenericClass<List<List<int>>>

and

GenericClass<List<List<ComplexCell>>>

are not the same base class