🚀 go-pugleaf

My apologies to the group, (and Borland) - I didn't even notice that Outlook 
Express had re-christened me. I think I have now changed my identity 
(File|Identity), but won't know for sure until I post this reply.

In the meantime, many thanks for your comprehensive reply - it was more than 
I dared hope for.

I'm a beginner when it comes to C#, and am struggling a bit. I am perhaps 
biased - but Delphi does have a certain elegance when it comes to this sort 
of stuff that is still hard to beat.

Cheers,
David.
"Joanna Carter [TeamB]" <joanna@nospam.for.me> wrote in message 
news:4677b67f@newsgroups.borland.com...
> Borland a �crit :
>
>> Referring to that posting from December last year re "class of"... I 
>> understand the use of Activator.CreateInstance(ClassType) as a 
>> replacement for the Delphi "class of" for use in a C# abstract class 
>> factory, but how would I use that ClassType reference to call a static 
>> method (eg public static DoIt()) which has been declared in the Class 
>> class?
>>
>> In Delphi I would simply retrieve the "class of" reference, (eg 
>> ClassClass - class of TClass), and call the function normally - eg 
>> TClass(ClassClass).DoIt;
>
> First, can I ask you to change your posting name from Borland ?
>
> Now, to the matter in hand.
>
> Don't forget that, in C#, static methods cannot be virtual. Therefore, you 
> have to redlclare the method in each and every derived class but simply 
> calling the static method on the base type will only call that method, not 
> the derived one.
>
> However, here is a simple example fo how to create a factory class that 
> will call the correct method, depending on the type passed in.
>
>   public class Base
>   {
>     public static void DoIt(int arg) { }
>   }
>
>   public class Derived : Base
>   {
>     public static void DoIt(int arg) { }
>   }
>
>   public static class Factory
>   {
>     public static void DoIt(Type type, int arg)
>     {
>       if (!typeof(Base).IsAssignableFrom(type))
>         throw new Exception("Type must derive from Base");
>
>       Type[] argTypes = new Type[] { typeof(int) };
>
>       MethodInfo mi = type.GetMethod("DoIt", argTypes);
>
>       object[] args = new object[] { arg };
>
>       mi.Invoke(null, args);
>     }
>   }
>
>     private void button1_Click(object sender, EventArgs e)
>     {
>       Type type = typeof(Derived);
>
>       Factory.DoIt(type, 123);
>     }
>
> You can also use the idea of a metaclass to achieve a more Delphi-like 
> syntax.
>
>   public class Base
>   {
>     #region metaclass
>
>     public class ClassReference
>     {
>       #region private members
>
>       private Type internalType;
>
>       #endregion
>
>       public void DoIt(int value)
>       {
>         MethodInfo methodInfo = internalType.GetMethod("DoIt", 
> BindingFlags.Public | BindingFlags.Static);
>
>         object[] args = new object[] { value };
>
>         methodInfo.Invoke(null, args);
>       }
>
>       #endregion
>
>       #region constructors
>
>       // default constructor
>       private ClassReference(Type type)
>       {
>         internalType = type;
>       }
>
>       #endregion
>
>       #region implicit conversion operator
>
>       public static implicit operator ClassReference(Type input)
>       {
>         if (!typeof(Shape).IsAssignableFrom(input))
>           throw new ArgumentException(String.Format("Type {0} must derive 
> from {1}", input.Name, typeof(Base).Name), "input");
>
>         return new ClassReference(input);
>       }
>
>       #endregion
>     }
>
>     #endregion
>
>     public static void DoIt(int value) {...}
>   }
>
>   public class Derived : Base
>   {
>     public static void DoIt() {...}
>   }
>
> This then allows the following calling syntax :
>
>   {
>     Base.ClassReference classRef = typeof(Derived);
>
>     classRef.DoIt(123);
>   }
>
> Is that what you are looking for ?
>
> Joanna
>
> -- 
> Joanna Carter [TeamB]
> Consultant Software Engineer