Could not load file or assembly Platform.Symphony.Soam.Net_64.dll displays when trying to run your .NET application

This issue is related to Visual Studio 2010's multi-targeting feature, which was first introduced with Visual Studio 2008 and .NET framework 4.0.

With the past few releases of Visual Studio, each Visual Studio release only supported a specific version of the .NET framework. For example, Visual Studio 2002 only worked with .NET 1.0, Visual Studio 2003 only worked with .NET 1.1, and Visual Studio 2005 only worked with .NET 2.0.

Starting with Visual Studio 2008, Microsoft supported the multi-targeting feature, which means that Visual Studio now supports targeting multiple versions of the .NET framework, and developers are able to take advantage of the new features Visual Studio provides without having to always upgrade existing projects and deployed applications in order to use a new version of the .NET framework library.

Now when you open an existing project or create a new one with Visual Studio 2008, you can choose which version of the .NET framework to work with, and the IDE will update its compilers and feature-set to match this. Among other things, this means that features, controls, projects, item-templates, and assembly references that do not work with that version of the framework will be hidden, and when you build your application, you'll be able to take the compiled output and copy it onto a machine that only has an older version of the .NET framework installed knowing that the application will work.

When IBM® Spectrum Symphony Microsoft compiler support extended to Visual Studio 2010, this feature became a little tricky because there are some default behavior changes between Visual Studio 2008 and 2010. Visual Studio 2008, by default, can pick up the correct dependency libraries even though a C# binary uses a higher version of .NET framework than its dependent libraries; Visual Studio 2010, by default, does not do it for .NET 4.0.The details follow.