Mono on Ubuntu: Package dotnet35 was not found in the pkg-config search path

I’m taking a C# and .NET class at ASU East. Our professor has example code that runs on Windows and the Mac (using Mono). I installed mono 2.8 from this link and I was able to get C# code to compile. However, when I tried to run my professor’s build script (he uses ant with some .NET extensions), I got the following error:

[dn:csc] Package dotnet35 was not found in the pkg-config search path.
[dn:csc] Perhaps you should add the directory containing `dotnet35.pc’
[dn:csc] to the PKG_CONFIG_PATH environment variable
[dn:csc] No package ‘dotnet35’ found
[dn:csc] error CS8027: Error running pkg-config. Check the above output.

To fix this, I set the value of PKG_CONFIG_PATH to /usr/local/mono/2.8/lib/pkgconfig (you’ll need to add this to your .bashrc). If you used the mono install-script without modification, then the value of PKG_CONFIG_PATH should be /opt/mono-2.8/lib.