Make custom file open by a custom program VB - vb.net

Question

How to make a file (.jkl extension for example) that when you open it, your custom program will pop-up.
For example:
I have a test.jkl file
If i double-click it, my program will be the one to read it.
Just like a .jpg file extension, when double-clicking the file, paint will pop-up and shows the image.
My code when changing the file ext is just simple
File.Copy(origFile, origFile.Replace("txt", "jkl")
File.Delete(origFile)
So now i have a .jkl file, now what I need to do is when the user double clicks the .jkl file, this program will automatically open, ask where to save it, and change it back to .txt to the path where the user wants to.
How can I do this?

Answer 1

Put it the form load event. it will write again and again. It won't destroy your PC. If you want to more carefully. Read registry check if it is exist then skip write again.
Code:
My.Computer.Registry.ClassesRoot.CreateSubKey(".jkl").SetValue_
("", "jkl", Microsoft.Win32.RegistryValueKind.String)
My.Computer.Registry.ClassesRoot.CreateSubKey_
("jkl\shell\open\command").SetValue("", Application.ExecutablePath & _
" ""%l"" ", Microsoft.Win32.RegistryValueKind.String)
link for demo project: http://www.codeproject.com/Articles/18594/File-Association-in-VB-NET

Answer 2

I don't think code is required. Once the file is saved as .jkl, right click the file and select the option "open with" -> "Choose default program" -> then browse to the exe you have written to save the file as .txt file.
If open with option is not available double click the file and select the option to select default program. Now browse to your exe.
The command line parameter args[0] is the file full name.
I have tried with C# code same can be done with VB code.
static void Main(string[] args)
{
Console.WriteLine("0: " + args[0]);
//Code to rename the file
Console.WriteLine("Done. Press enter");
Console.ReadKey();
}
VB Code using online converter
Private Shared Sub Main(args As String())
Console.WriteLine("0: " + args(0))
'Code to rename the file
Console.WriteLine("Done. Press enter")
Console.ReadKey()
End Sub