Add TransformBy(transformation) to the ICurve interface?

Can you add the method TransformBy(transformation) to the ICurve interface also? This is because I believe that the TransformBy method will always be available for the classes that implement ICurve interface, because those classes must necessarily be Entity class type?

 

Now I have to cast the entity to Entity before I use the TransformBy method, ie:

 

 private static ICurve GetTransformation(ICurve originalFace, Transformation transformation)
 {
     
     var mirrorPath = (ICurve)originalFace.Clone();
     ((Entity)mirrorPath).TransformBy(transformation);  //the casting here is a minor eye sore. 
     return mirrorPath;
 }