/// <summary>

/// Create an associaten for a file extension in the windows registry

/// CreateAssociation(@"vendor.application",".tmf","Tool file",@"C:\Windows\SYSWOW64\notepad.exe",@"%SystemRoot%\SYSWOW64\notepad.exe,0");

/// </summary>

/// <param name="ProgID">e.g. vendor.application</param>

/// <param name="extension">e.g. .tmf</param>

/// <param name="description">e.g. Tool file</param>

/// <param name="application">e.g.  @"C:\Windows\SYSWOW64\notepad.exe"</param>

/// <param name="icon">@"%SystemRoot%\SYSWOW64\notepad.exe,0"</param>

/// <param name="hive">e.g. The user-specific settings have priority over the computer settings. KeyHive.LocalMachine  need admin rights</param>

public static void CreateAssociation(string ProgID, string extension, string description, string application, string icon, KeyHiveSmall hive = KeyHiveSmall.CurrentUser)

{

    RegistryKey selectedKey = null;

    switch (hive)

    {

        case KeyHiveSmall.ClassesRoot:

            Microsoft.Win32.Registry.ClassesRoot.CreateSubKey(extension).SetValue("", ProgID);

            selectedKey = Microsoft.Win32.Registry.ClassesRoot.CreateSubKey(ProgID);

            break;

        case KeyHiveSmall.CurrentUser:

            Microsoft.Win32.Registry.CurrentUser.CreateSubKey(@"Software\Classes\" + extension).SetValue("", ProgID);

            selectedKey = Microsoft.Win32.Registry.CurrentUser.CreateSubKey(@"Software\Classes\" + ProgID);

            break;

        case KeyHiveSmall.LocalMachine:

            Microsoft.Win32.Registry.LocalMachine.CreateSubKey(@"Software\Classes\" + extension).SetValue("", ProgID);

            selectedKey = Microsoft.Win32.Registry.LocalMachine.CreateSubKey(@"Software\Classes\" + ProgID);

            break;

    }

    if (selectedKey != null)

    {

        if (description != null)

        {

            selectedKey.SetValue("", description);

        }

        if (icon != null)

        {

            selectedKey.CreateSubKey("DefaultIcon").SetValue("", icon, RegistryValueKind.ExpandString);

            selectedKey.CreateSubKey(@"Shell\Open").SetValue("icon", icon, RegistryValueKind.ExpandString);

        }

        if (application != null)

        {

            selectedKey.CreateSubKey(@"Shell\Open\command").SetValue("", "\"" + application + "\"" + " \"%1\"", RegistryValueKind.ExpandString);

        }

    }

    selectedKey.Flush();

    selectedKey.Close();

}

/// <summary>

/// Creates a association for current running executable

/// </summary>

/// <param name="extension">e.g. .tmf</param>

/// <param name="hive">e.g. KeyHive.LocalMachine need admin rights</param>

/// <param name="description">e.g. Tool file. Displayed in explorer</param>

public static void SelfCreateAssociation(string extension, KeyHiveSmall hive = KeyHiveSmall.CurrentUser, string description = "")

{

    string ProgID = System.Reflection.Assembly.GetExecutingAssembly().EntryPoint.DeclaringType.FullName;

    string FileLocation = System.Reflection.Assembly.GetExecutingAssembly().Location;

    CreateAssociation(ProgID, extension, description, FileLocation, FileLocation + ",0", hive);

}