Question

NOTE: .NET Pad code HERE.

I have a base class that takes a generic type parameter.

Each class it will form the base of has a corresponding Collection Class which consists of only this:

public class List_SomeType : List<SomeTime> {
  public List_SomeType() {
  }
}

That’s it: It only a List<T> container.

However, it is posing a problem in my base class because one of the methods is to return this collection.

I tried creating the following Get method, which made perfect sense to me:

public TList Get() {
  var list = new TList();
  using (var cmd = new SqlCommand(SP_GET, m_openConn)) {
    cmd.CommandType = CommandType.StoredProcedure;
    using (var r = cmd.ExecuteReader()) {
      while (r.Read()) {
        list.Add(FillDataRecord(r));
      }
    }
    cmd.Connection.Close();
  }
  return list;
}

public class TList : List<T> {
  public TList() { }
}

In my derived class, I planned to call this base class as follows:

public class BuyerDB : DAL_Base<Buyer> {

  private static BuyerDB one;

  static BuyerDB() {
    one = new BuyerDB();
  }

  public static BuyerList GetBuyerList() {
    return (BuyerList)one.Get(); // <= ERROR HERE!
  }

}

The ERROR HERE states:

Cannot convert type ‘DAL_Base.TList’ to ‘BuyerList’

How do I convert back to a collection of my generic types?

EDIT:

Mark wants to know what BuyerList is.

I thought that was understood from what I wrote.

Apparently not, so here it is:

public class BuyerList : List<Buyer> { }

That’s all!

Answer 1

This compiles:

public static BuyerList getBuyerList() {
  var result = new BuyerList();
  result.AddRange(one.Get());
  return result;
}

I am not sure why the other list would not work, but I’d guess it has something to do with checks done inside of the C# language.