C# Windows 'Open With >' Context menu behaviour [duplicate]

Answer 1

The Open With command just passes the path of the file as the first argument to the application so all you need to do is

public static void Main(string[] args)
{
    if(args[0] != null)
    {
       //args[0] contans a path to the file do whatever you need to do to display it
    }
    else
    {
       //Start normally
    }
}

To automaticly put your program in the open with list you will need to add some reg keys in HKEY_CLASSES_ROOT\YOUR_EXT\. Here is a SO answer saying how to do it

Or you could just add it by hand to the open with list the normal way.

Answer 2

Take a look at this blog post: Shell Extensions - Context Menu. It has code for a simple "wrapper" to some COM hooks to the Windows shell context menu. Put it in the GAC and when you right-click, your menu will be included as a sub-menu of the right-click context menu.

As far as strictly using "Open With..." to make your application show up ONLY for files it can open, that's a little easier. These are managed by Windows using registry keys in two places in the registry:

1. HKEY_CURRENT_USER \ Software \ Microsoft \ Windows \ CurrentVersion \ Explorer \ FileExts \ .FileExtension \ OpenWithList (install for current user)
2. HKEY_CLASSES_ROOT \ .FileExtension \ OpenWithList (install for all users)

Take a look at some of the existing ones using regedit, then use the Registry class to create a new key for the extension you want.