C#

<code>

    class Shell32Utils
    {
        const int FILENOASSOCIATED = 31;
        const int FILENOTFOUND = 2;
        const int PATHNOTFOUND = 3;
        const int SUCCESS = 32; //and longer
        const int BADFORMAT = 11;

        

        [DllImport("shell32", EntryPoint = "FindExecutable")]
        static extern int FindExecutable(string file, string directory, [MarshalAs(UnmanagedType.LPStr)] StringBuilder result);


        public static string Find(string file)
        {
            string fileName=System.IO.Path.GetFileName(file);
            string filePath = System.IO.Path.GetDirectoryName(file)+"\\";

            System.Text.StringBuilder res = new StringBuilder(1024);

            int stat = FindExecutable(fileName, filePath,  res);

            switch (stat)
            {
                case FILENOASSOCIATED: throw new Exception("File Not Associated");
                case FILENOTFOUND: throw new Exception("FileNot Found");

                case PATHNOTFOUND: throw new Exception("Path not Found");

                case BADFORMAT: throw new Exception("Bad Format");

                default: if (stat >= SUCCESS) return res.ToString();
                    else throw new Exception("Unknown Error");
            }
        }       
    }

</code>

foreach (InputLanguage lang in InputLanguage.InstalledInputLanguages)
    if (lang.LayoutName == "Farsi")
    {
        InputLanguage.CurrentInputLanguage = lang;
        break;
    }