Because with new versions of connectors or another external libraries there may be some compatibility issues, developers of .NET applications may find themselves in the next situation

• on developer machine they are forced to install these new versions of the external libraries or modules
• on the client machine, with different software or hardware configuration, there are compatibility issues with the new library/module (it can’t be installed or it generate runtime exceptions)

The scenario that I have encountered is this:

• .NET Windows application that uses 2.0 .NET framework
• the application was developed in Visual Studio 2008
• the application connect to a MySQL database using connector/NET from MySQL.com
• the application uses Crystal Reports as reporting services

After updating the IDE to VS2010 some problems have emerged:

• the older version (v 5.2.7) of the MySQL connector/NET has compatibility issues with VS2010 (see How to connect to MySQL database from Visual Studio VS2010 – problems with NET connectors for details), so I was forced to install 6.3.4 version (the latest version at the time of this post)
• the MySQL connector has problems installing on Windows XP
• VS2010 uses Crystal Reports for Visual Studio 2010 Beta release but this versions does not have yet a redistributable package
• on the client machine, it has been installed the Crystal Reports 2008 redistributable packages to deploy a Microsoft Visual Studio 2010 project that embeds the Crystal Reports for Visual Studio 2010 Beta release (particular solution: Deploying Crystal Reports for Visual Studio 2010 Beta on http://www.sdn.sap.com/irj/sdn/sbo-solutions)

The solution that allows the deployment of .NET applications that use modules/libraries with different version than the modules used in development:

• open/add the configuration file of the WinForm .NET application  –  App.config (to add this file, in Solution explorer right click on the project name then Add -> New item -> Application Configuration File)
• the configuration file is an XML file that can be edited;
• add next settings between the <configuration></configuration> attributes (the solution for Crystal Reports is better described in Deploying Crystal Reports for Visual Studio 2010 Beta on http://www.sdn.sap.com/irj/sdn/sbo-solutions)

• using App.config configuration file, we instruct the .NET process to use modules/libraries with different version than the ones used in development
• this solution works if there are not major differences between functions described in these modules and used by the application
• when deploying the WinForm application do not forget to take also the [ApplicationName].exe.config that is an editable XML (it can be edited on the client machine) file identical with the App.config file
• for ASP.NET applications the solution is similar because the settings are added also to <configuration></configuration>