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Generic List Conversion

, 6 Sep 2010 CPOL
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How to convert a generic List of derived types to a generic list of base types.

The Scenario

You have a base class Mammal and a derived class Dog.

public abstract class Mammal
public class Dog : Mammal

You create a list of dogs List<Dog>.

The Problem

You want to have a list of mammals List<Mammal> that is built from the list of dogs. If you try either an implicit or explicit cast you will be told that it isn't possible!

The Solution

This little function will create a list of mammals from a list of dogs.

public static List<TBase> DerivedConverter<TBase, TDerived>(List<TDerived> derivedList)
    where TDerived : TBase
    return derivedList.ConvertAll<TBase>(
       new Converter<TDerived, TBase>(delegate(TDerived derived)
           return derived;

To use it:

List<Base> listBase = DerivedConverter<Base, Derived>(listDerived);

In our scenario Base would be Mammal and Derived would be Dog.

You could use the same function for Human, Dolphin, Cat etc, or any other derived class list to base class list without having to write a new converter.


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

CEO Dave Meadowcroft
United Kingdom United Kingdom
No Biography provided

Comments and Discussions

GeneralReason for my vote of 5 Thank you! Nice tip! PinmemberSimon Dufour7-Sep-10 3:41 
GeneralGood job! The DerivedConverter method could be a bit simple... PinmemberKubajzz6-Sep-10 3:04 

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