We added some new features in our code this week that required System.Windows.Forms.DataVisualization. No problem until we ran the nant build and it failed with:
The type or namespace name 'DataVisualization' does not exist in the namespace 'System.Windows.Forms' (are you missing an assembly reference?)
We tried copying the DLL several places, even though we later discovered this was unnecessary. The DLL exists in the GAC and we only need to add the reference to the DLL in the nant .build file.
It turns out that the problem exists in the nant.exe.config file we use. This file notoriously has several errors and needs to be updated. I found a copy of nant.exe.config that we need at http://pastebin.com/YxxaKADS. I simply copied the 2 lines at 121 and 122 and pasted them into our nant.exe.config build file and the problem was solved.
121. <include name="System.Windows.Forms.DataVisualization.Design.dll" / >
122. <include name="System.Windows.Forms.DataVisualization.dll" / >