How to make a C# Application work as the default program for certain files? [duplicate]

Question

My application has a picture box in it. When I open an image in Windows, instead of the default program that opens to show that image, I want to use my own application and have that program containing the picture box show the image.

Answer 1

I did this recently, though I used a different action, not the default Open action.

First you find out file type of some extension, say .jpg:

var imgKey = Registry.ClassesRoot.OpenSubKey(".jpg")
var imgType = key.GetValue("");

Then you find out the path to your executable and build the "command string":

String myExecutable = Assembly.GetEntryAssembly().Location;
String command = "\"" + myExecutable + "\"" + " \"%1\"";

And register your executable to open files of that type:

String keyName = imgType + @"\shell\Open\command";
using (var key = Registry.ClassesRoot.CreateSubKey(keyName)) {
    key.SetValue("", command);
}