Open picture from application and edit with default picture edit application ?

[C# Programming]

I wrote small application - and i want to add some new feature that in case the user double click on the picture then the default edit application ( for example paint.exe application ) will be open the current picture.

My question are:
1. how can i know what is the default edit picture application that appear on current machine ( how can i know it in run-time ? )
2. how to open the picture in this application in run-time ?

Thanks.