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();