Couldn't help but detect a hint of malevolence in the depiction of faith, so here's my own more reasonable version in response:
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A common scenario in C# I find is that I would like to:
I still want them to show up as warnings, which is to say that I don't want them to disappear altogether. 'CS0618 Obsolete' is a good example of this.
This cannot be achieved through the C# Project Properties editor, but it can be done by manually editing the .csproj file to add these two MSBuild properties:
<TreatWarningsAsErrors>true</TreatWarningsAsErrors>
<WarningsNotAsErrors>618</WarningsNotAsErrors>
This is vaguely referred to in the docs here, and the list of error codes can be found here.
Setting up a new computer I somehow managed to break Visual Studio macros. Finally found this, which fixed it. (See the Workaround tab).
Basically delete this magical file, then rerun the VS installer:
%ProgramFiles(x86)%\Microsoft Visual Studio 9.0\Common7\IDE\1033\Microsoft.VSDesignerUI.dll