To load project references from a sub directory in C# and VB.NET you simply need to add the element to your app.config file.
assemblyBinding: Contains information about assembly version redirection and the locations of assemblies.
configuration: The root element in every configuration file used by the common language runtime and .NET Framework applications.
runtime: Contains information about assembly binding and garbage collection.
To get the path of the active app.config file in C# and VB.NET you can use the following snippet