How to associate a file extension to the current executable in C#

Question

I\'d like to to associate a file extension to the current executable in C#. This way when the user clicks on the file afterwards in explorer, it\'ll run my executable with t

Answer 1

There are two cmd tools that have been around since Windows 7 which make it very easy to create simple file associations. They are assoc and ftype. Here's a basic explanation of each command.

• Assoc - associates a file extension (like '.txt') with a "file type."
• FType - defines an executable to run when the user opens a given "file type."

Note that these are cmd tools and not executable files (exe). This means that they can only be run in a cmd window, or by using ShellExecute with "cmd /c assoc." You can learn more about them at the links or by typing "assoc /?" and "ftype /?" at a cmd prompt.

So to associate an application with a .bob extension, you could open a cmd window (WindowKey+R, type cmd, press enter) and run the following:

assoc .bob=BobFile
ftype BobFile=c:\temp\BobView.exe "%1"

This is much simpler than messing with the registry and it is more likely to work in future windows version.

Wrapping it up, here is a C# function to create a file association:

public static int setFileAssociation(string[] extensions, string fileType, string openCommandString) {
    int v = execute("cmd", "/c ftype " + fileType + "=" + openCommandString);
    foreach (string ext in extensions) {
        v = execute("cmd", "/c assoc " + ext + "=" + fileType);
        if (v != 0) return v;
    }
    return v;
}
public static int execute(string exeFilename, string arguments) {
    ProcessStartInfo startInfo = new ProcessStartInfo();
    startInfo.CreateNoWindow = false;
    startInfo.UseShellExecute = true;
    startInfo.FileName = exeFilename;
    startInfo.WindowStyle = ProcessWindowStyle.Hidden;
    startInfo.Arguments = arguments;
    try {
        using (Process exeProcess = Process.Start(startInfo)) {
            exeProcess.WaitForExit();
            return exeProcess.ExitCode;
        }
    } catch {
        return 1;
    }
}