I want to build cad tools which will be used in municipality applications on esri.Let me tell the question.The user wants to edit on the map and does it by using IEditSketch.But i want to write a custom IEditSketch.So i want to implement that interface.Can u share your experiments about it.Thanks...
Your question is probably too broad, but in any case I strongly suggest that you consult the Editor framework customizations document included in the SDK.
It provides the necessary conceptual overview as well as useful samples which will come handy.
Also note that at ArcGIS 10, the edit sketch components have been expanded with shape constructors (which you'll find among the mentioned samples). They are mostly implemented via IShapeConstructor interface.