Converting a List of Base type to a List of Inherited Type

Question

I would be certain that this question addresses something that would have been brought up in a previous question, but I was unable to find it.

There is a method in a C# class that takes as a parameter a generic List of a Base Class. I need to pass a list of an inherited class and do not know exactly how to do this. I am getting an error in my attempts. Below is sample code to illustrated this:

public class A
{
   public static void MethodC(List<A>)
   {
       // Do Something here with the list
    }
}
public Class B : A
{
   // B inherits from A, A is the Base Class   
}

// Code utilizing the above method 
List<B> listOfB = new List<B>();
A.MethodC( (List<A>) listOfB );  // Error: this does not work
A.MethodC( listOfB.ToList<typeof(A)>() ); // Error: this does not work
A.MethodC( listOfB.ConvertAll<A>(typeof(A)) ); // Error: this does not work
// how can I accomplish this?  It should be possible I would think

Note: Here is my final working Method as a reference. I got an even better solution to my problem, but technically it wasn't an answer to the question, since my question was phrased impropertly.

 public static DataTable 
    ObjectCollectionToDataTable<GLIST>
      (List<GLIST> ObjectCollection) where GLIST 
              : BaseBusinessObject
        {
            DataTable ret = null;

            if (ObjectCollection != null)
            {
                foreach ( var b in ObjectCollection)
                {

                    DataTable dt = b.ToDataTable();
                    if (ret == null)
                        ret = dt.Clone();
                    if (dt.Rows.Count > 0)
                        ret.Rows.Add(dt.Rows[0].ItemArray);
                }
            }

            return ret;
        }

Answer 1

If you have linq available you can do

var ListOfA = ListOfB.Cast<A>().ToList();