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

Here's a complete example:

public class FileAssociation
{
    public string Extension { get; set; }
    public string ProgId { get; set; }
    public string FileTypeDescription { get; set; }
    public string ExecutableFilePath { get; set; }
}

public class FileAssociations
{
    // needed so that Explorer windows get refreshed after the registry is updated
    [System.Runtime.InteropServices.DllImport("Shell32.dll")]
    private static extern int SHChangeNotify(int eventId, int flags, IntPtr item1, IntPtr item2);

    private const int SHCNE_ASSOCCHANGED = 0x8000000;
    private const int SHCNF_FLUSH = 0x1000;

    public static void EnsureAssociationsSet()
    {
        var filePath = Process.GetCurrentProcess().MainModule.FileName;
        EnsureAssociationsSet(
            new FileAssociation
            {
                Extension = ".binlog",
                ProgId = "MSBuildBinaryLog",
                FileTypeDescription = "MSBuild Binary Log",
                ExecutableFilePath = filePath
            },
            new FileAssociation
            {
                Extension = ".buildlog",
                ProgId = "MSBuildStructuredLog",
                FileTypeDescription = "MSBuild Structured Log",
                ExecutableFilePath = filePath
            });
    }

    public static void EnsureAssociationsSet(params FileAssociation[] associations)
    {
        bool madeChanges = false;
        foreach (var association in associations)
        {
            madeChanges |= SetAssociation(
                association.Extension,
                association.ProgId,
                association.FileTypeDescription,
                association.ExecutableFilePath);
        }

        if (madeChanges)
        {
            SHChangeNotify(SHCNE_ASSOCCHANGED, SHCNF_FLUSH, IntPtr.Zero, IntPtr.Zero);
        }
    }

    public static bool SetAssociation(string extension, string progId, string fileTypeDescription, string applicationFilePath)
    {
        bool madeChanges = false;
        madeChanges |= SetKeyDefaultValue(@"Software\Classes\" + extension, progId);
        madeChanges |= SetKeyDefaultValue(@"Software\Classes\" + progId, fileTypeDescription);
        madeChanges |= SetKeyDefaultValue($@"Software\Classes\{progId}\shell\open\command", "\"" + applicationFilePath + "\" \"%1\"");
        return madeChanges;
    }

    private static bool SetKeyDefaultValue(string keyPath, string value)
    {
        using (var key = Registry.CurrentUser.CreateSubKey(keyPath))
        {
            if (key.GetValue(null) as string != value)
            {
                key.SetValue(null, value);
                return true;
            }
        }

        return false;
    }