C # External methods

The Using system;using system.runtime.interopservices;using system.text;/* * External method is a method that is not implemented in a declaration, and is often written in a programming language other than C #.  * 1, marked with the extern modifier, is not implemented in the declaration of the class, its implementation is replaced by a semicolon  * 2, the Declaration and the implementation of the connection is dependent on the implementation. Often use the DllImport feature to complete  */namespace externmethod{    class myclass    {        [ DllImport ("kernel32", Setlasterror=true)]        public static  extern int GetCurrentDirectory (int a,stringbuilder b);   }    class program    {        static void M Ain (string[] args)         {            const int maxdirlength = 250;&nbs P           StringBuilder sb = new StringBuilder ();            SB. Length = maxdirlength;            myclass.getcurrentdirectory (maxdirlength, SB);  & nbsp         Console.WriteLine (SB);            CoNsole. ReadKey ();       }   }

C # External methods