Why can't I declare C# methods virtual and static?

I don't think you are crazy. You just want to use what is impossible currently in .NET.

Your request for virtual static method would have so much sense if we are talking about generics. For example my future request for CLR designers is to allow me to write intereface like this:

public interface ISumable<T>
{
  static T Add(T left, T right);
}

and use it like this:

public T Aggregate<T>(T left, T right) where T : ISumable<T>
{
  return T.Add(left, right);
}

But it's impossible right now, so I'm doing it like this:

    public static class Static<T> where T : new()
    {
      public static T Value = new T();
    }

    public interface ISumable<T>
    {
      T Add(T left, T right);
    }

    public T Aggregate<T>(T left, T right) where T : ISumable<T>, new()
    {
      return Static<T>.Value.Add(left, right);
    }

Virtual static methods don't make sense. If I call HelperClass.HelperMethod();, why would I expect some random subclass' method to be called? The solution really breaks down when you have 2 subclasses of HelperClass - which one would you use?

If you want to have overrideable static-type methods you should probably go with:

• A singleton, if you want the same subclass to be used globally.
• A tradition class hierarchy, with a factory or dependency injection, if you want different behavior in different parts of your application.

Choose whichever solution makes more sense in your situation.

Indeed, this can be done in Delphi. An example:

type
  TForm1 = class(TForm)
    procedure FormShow(Sender: TObject);
  end;

  TTestClass = class
  public
    class procedure TestMethod(); virtual;
  end;

  TTestDerivedClass = class(TTestClass)
  public
    class procedure TestMethod(); override;
  end;

  TTestMetaClass = class of TTestClass;

var
  Form1: TForm1;

implementation

{$R *.dfm}

class procedure TTestClass.TestMethod();
begin
  Application.MessageBox('base', 'Message');
end;

class procedure TTestDerivedClass.TestMethod();
begin
  Application.MessageBox('descendant', 'Message');
end;


procedure TForm1.FormShow(Sender: TObject);
var
  sample: TTestMetaClass;
begin
  sample := TTestClass;
  sample.TestMethod;
  sample := TTestDerivedClass;
  sample.TestMethod;
end;

Quite interesting. I no longer use Delphi, but I recall being able to very easily create different types of controls on a custom designer canvas using the metaclass feature: the control class, eg. TButton, TTextBox etc. was a parameter, and I could call the appropriate constructor using the actual metaclass argument.

Kind of the poor man's factory pattern :)