How to call method of generic class from non generic class using dynamic?

Question

I want to call a method of generic class from non generic class which doesn't know the type.

interface IShape
{
    SomeType AProperty;     // Edit 2, sorry this should be a property.
}

interface IShapeEditor
{
}

class ShapeEditorBase : IShapeEditor
{
}

class RectangleEditor<T> : ShapeEditorBase where T : IShape
{
    void Offset(T shape, int x, int y)
    {
    }
}

// This class must not be a generic class.
class OffsetRectangleButton
{
    void ButtonPressed(IShapeEditor editor)
    {
        IShape shape = ashape; // from somewhere
        dynamic editorInstance = editor;
        editorInstance.Offset(shape, 1, 1); // Will trigger an exception here!
    }
}

But it triggered an exception, it said C# cannot find Offset method in ShapeEditorBase.
Why is it not the RectangleEditor, but ShapeEditorBase?
How can I solve that problem? Or maybe a refactoring suggestion?

If possible without reflection (I heard it is not good).

===================

Edit for additional information:
- All code snippets are in a framework which is a Control.
- Application gives type via generic
- OffsetRectangleButton or other buttons for rectangle know everything about the methods because they are in a component/dll.

====================

Edit 3
- Make the code as similar as possible to the problem
- I rewrite the code to make the previous answers understandable instead of editing the previous code
- Please see OffsetRectangleAction
- Question: Is the interface IRectangleEditor is correct? (And I can continue to solve OffsetRectangleAction)
- Question: Or there are better solution?

// =========================================
// Shape Display Component (a Winform Panel)
// =========================================

// In reality, rectangle is very complex implementation.
interface IRectangle // For rectangle display
{
    Rectangle Rectangle { get; set; }
}

interface ILine // ICircle etc for other displays
{
    Line Line { get; set; }
}

// Edit/Offset actions interface. It is represented by a button.
interface IAction
{
    void Run(IShapeDisplay display);
}

// Container of all display's actions.
interface IActionContainer
{
    IList<IAction> Actions; // Every action is related to a control (button, edit box, etc).
}   

// Please see "OffsetRectangleAction".
// This class is container of all RectangleDisplays actions (as buttons in UI).
// This is also important, because this class shows why OffsetRectangleAction must not be generic.
// If OffsetRectangleAction is generic, then this class must be generic because it has OffsetRectangleAction.
// If this class generic, then in user interface has more than one OffsetRectangleAction buttons are created.
// And each OffsetRectangleAction edit certain type of Rectangle generic.
class RectangleActionContainer : IActionContainer
{
    // List of all actions/buttons
    IList<IAction> Actions;    

    RectangleActionContainer()
    {
        // It must be able to edit various types of rectangle.
        this.Actions.Add(new EditAction());
        this.Actions.Add(new OffsetRectangleAction());
    }
}

// This class must not be a generic class. Please see RectangleActionContainer class.
// This is the most important problem!!!!!!!!!!!!!!!!!!!!!!!!!
// How can I access RectangleDisplay.RetctangleEditor.Offset or Edit
class OffsetRectangleAction: IAction // Similar also EditRectangleAction, InflateRectangleAction
{
    void Run(IShapeDisplay display)
    {
        IRectangle rectangle = this.GelectedRectangle(); // from somewhere

        // How to make it runs properly without exception.
        dynamic rectangleDisplayInstance = display;
        dynamic editHandler = rectangleDisplayInstance.EditHandler;
        editHandler.Offset(rectangle, 1, 1); // Will trigger an exception here!
    }
}

// RectangleEditor interface to edit rectangles and as rectangles container.
interface IRectangleEditor<T> where T : IRectangle // Generic because there are many type rectangle for various purposes. 
{
    IList<T> Rectangles { get; } // List of rectangle to be edited/visualized.

    Edit(T rect, Rectangle dimension);  

    Offset(T rect, double x, double y);
}

// Shape display interface
interface IShapeDisplay
{
    IActionContainer ActionContainer { get; }

    void Draw(Graphics canvas);
}

// Base of all displays (rectangle, line, circle)
class ShapeDisplayBase : IShapeDisplay
{
    IActionContainer ActionContainer { get; private set; }

    virtual void Draw(Graphics canvas)
    {
    }
}

// Rectangle Display.
// Controller for displaying and bussines logic of rectangle shapes.
// ShapeDisplayBase inherited also for Line, Circular etc displays.
class RectangleDisplay<T> : ShapeDisplayBase where T : IShape
{
    IRectangleEditor<T> RectangleEditor { get; private set; }

    RectangleDisplay<T>(IRectangleEditor<T> editor)
    {
        this.RectangleEditor = editor;
    }

    override void Draw(Graphics canvas)
    {
    }
}

// Controller for the whole shape displays (Rectangle, Line, Circle etc.)
class ShapeDisplaysController
{
    IList<IActionContainer> ActionContainers { get; private set; } // Action container for all displays (rectangle, line, etc)

    IList<IShapeDisplay> ShapeDisplays { get; private set; } // Can be RectangleDisplay, LineDisplay, CircularDisplay

    void RegisterDisplay(IShapeDisplay display)
    {
       this.ShapeDisplays = display;

       // A type of displays can only one action container (eg: many rectangle types can be edited only with one edit button)
       if (!ActionContainer.Contains(display))
       {
           ActionContainers.Add(display.ActionContainer);
       }
    }

    // Show all shape display objects.
    void Draw(Graphics canvas)
    {
        foreach(var display in this.ShapeDisplays)
        {
            display.Draw(canvas);
        }
    }
}

// ==========================
// Application 
// ==========================

class RoundedRectangleEditHandler<T> : IRectangleEditor<T> where T : IRectangle
{
     IList<T> Rectangles { get; private set;} // List of rectangle to be edited/visualized.
     implementation...
}

class FillRectangleEditHandler<T> : IRectangleEditor<T> where T : IRectangle
{
     IList<T> Rectangles { get; private set;} // List of rectangle to be edited/visualized.
     implementation...
}

// There are many application that use ShapeViewer component.
// And every application has their own rectangle type, so we decided to use generic.
class ShapeViewerApp: Form
{
    // Visualization control for shape.
    private ShapeDisplaysController myShapeDisplaysController;

    // Show shape list in grid.
    private GridController myGridController;

    static void Main()
    {
        this.myShapeDisplaysController = new ShapeDisplaysController();

         var roundedRectangleEditHandler = new RoundedRectangleEditHandler<RoundedRect>();
         var roundedRectangleDisplay = new RoundedRectangleDisplay<RoundedRect>(roundedRectangleEditHandler);

         var fillRectangleEditHandler = new FillRectangleEditHandler<FillRectangle>();
         var fillRectangleDisplay = new FillRectangleDisplay<FillRectangle>(fillRectangleEditHandler);           

         this.myShapeDisplaysController.Register(fillRectangleDisplay);
         this.myShapeDisplaysController.Register(roundedRectangleDisplay);
         this.myShapeDisplaysController.Register(lineDisplay);
         this.myShapeDisplaysController.Register(circleDisplay);

         // ShapeDisplaysController is a Winform Panel UI.
         this.Controls.Add(this.myShapeDisplaysController.Control);
         this.ShowDialog();
    }
}

Answer 1

How about moving you Offset to IShapeEditor and implement it in ShapeEditorBase? Then you wouldn't need to use dynamic.

class ShapeEditorBase : IShapeEditor
{
    public void Offset(IShape shape, int x, int y)
    {
    }
}

class RectangleEditor<T> : ShapeEditorBase where T : IShape
{
}

Answer 2

IShapeEditor doesn't contain your Offset method, and thus the program doesn't know that the method exists on that object. You could cast it as that type, if you were certain that's what it is and that would enable you to avoid the dynamic keyword.

I suggest you add the method to IShapeEditor, or otherwise use the exact type you care about, since the class you're implementing refers to Rectangles, it only makes sense that it would be concerned about only Rectangles, and not any other IShape.