Question

I have a class MyClass, and I would like to override the method ToString() of instances of List:

class MyClass
{
    public string Property1 { get; set; }
    public int Property2 { get; set; }
    /* ... */
    public override string ToString()
    {
        return Property1.ToString() + "-" + Property2.ToString();
    }
}

I would like to have the following:

var list = new List<MyClass>
            {
                new MyClass { Property1 = "A", Property2 = 1 },
                new MyClass { Property1 = "Z", Property2 = 2 },
            };

Console.WriteLine(list.ToString());   /* prints: A-1,Z-2 */

Is it possible to do so? Or I would have to subclass List<MyClass> to override the method ToString() in my subclass? Can I solve this problem using extension methods (ie, is it possible to override a method with an extension method)?

Thanks!

Answer 1

You’ll need to subclass to override any method. The point of generics is to say that you want the same behaviour regardless of the type of T. If you want different behaviour for a specific type of T then you are breaking that contract and will need to write your own class:

public class MyTypeList : List<MyClass>
{
    public override string ToString()
    {
        return ...
    }
}

---

Edited to add:

No, you can’t override a method by creating an extension, but you could create a new method with a different signature that is specific to this list type:

public static string ExtendedToString(this List<MyClass> list)
{
     return ....
} 

Used with

List<MyClass> myClassList = new List<MyClass>
string output = myClassList.ExtendedToString();

I still think you’re better off subclassing though…