How to Compile SWMM 5 in Visual Studio 2010 Express
Download the newest SWMM 5 code(Figure 1) from http://www.epa.gov/nrmrl/wswrd/wq/models/swmm/#Downloads and then make a new directory on your computer. We will call it c:\newSWMM5Code with a subdirectory C:\newSWMMCode\VC2005_DLL in which the attached vcxproj file is placed. The source code from the EPA should be placed on C:\newSWMMCode. You can then open up the file swmm5_ms.vcxproj and make a new SWMM 5 DLL model with your code modifications (if needed).
Figure 1. The source code from the EPA for SWMM5.