This paper describes the porting of the ''Tcl'' Freiburg client to ''C#''.

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'''1. What is C#'''

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''C#'' is a new programming language introduced by Microsoft as answer of
the growing popularity of Java from Sun Systems

   * http://www.c-sharpcorner.com/
   * http://www.csharp-station.com/

the ''C#'' Framework is available in a GNU edition called ''mono'' and a original
edition called ''Microsoft .NET Framework SDK''

   * http://msdn.microsoft.com/netframework/
   * http://www.mono-project.com/about/index.html

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'''2. Compare C# and Freiburg'''

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''C#'' as a very new programming languages introduces a couple of new technology's
including a language independent abstraction layer available for ''C#'', Visual Basic,
JScript and C++ and other.
Freiburg was born to provide a language independent interface to services usable
for Unix, Windows and Mac-OS.
There are at least a common strategic target between .NET and Freiburg but available
with two totally independent technologies:

   * .NET : mapping all supported programming languages into a common language called ''Common Language Runtime'' or short '''CLR''' using a language independent byte-code
   * Freiburg: using a technology layer to link different services (called server) into different programming languages (called clients) using a data-bus

From the programmer point of view everything looks equal but ''Freiburg'' supports all
available languages and ''C#'' only a limited range

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'''3. link the libFreiburg with Tcl and C#'''

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   ''Tcl'':   ''Tcl'' has a C library and C-API providing all features needed to link a C library with ''Tcl''. search this wiki for additional information. (is a link available?)

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   ''C#'':   the ''C#'' way to link a dynamic library with the language is totally different

   1. no C-API available
   2. every link between a ''C#'' Method and a library function is done 'on the fly' using ''Marshalling'' of native C data types with ''C#'' data types
   3. ''C#'' directly support common C language features likes ''struct'' and ''pointer'' using the ''unsafe'' keyword

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''everything sounds very good for C#, but the problems are in detail''

   * If you are using SWING to create the ''C#'' interface something interesting happen. SWING creates a ''C'' interface library and a ''C#'' wrapper for this library. (bad)
   * To avoid using pointers in ''C#'' every pointer like operation have to be transformed into a procedure operation -> this will blow up your interface (slow and bad)
   * you end up with an interface using ''C#'' and a interface using ''C'' (double workload)
   * to avoid double interfaces you end up with ''unsafe'' code (non portable in ''C#'')
   * to create a ''fast'' interface ''unsafe'' code is needed with 2 restriction's:
      1. private pointers are '''not''' type safe because only one ''C#'' type IntPtr (e.g. void*) is available (very bad)
      2. public pointer are type safe because the public ''C'' structs can be included into ''C#'' using ''C#'' syntax -> every public ''C'' struct have to be duplicated into ''C#'', every change on one side have to be reproduced on the other side (very very very bad)

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