You can have multiple wine prefix on your machine, each running as a separate wine. So you can make a 32 bits prefix and install dotnet2 in it:

This will create a new wineprefix (.wine32 in your home) and configure it as 32 bits:

WINEARCH=win32 WINEPREFIX=~/.wine32 winecfg

You can use it this way combined with winetricks to configure WINEARCH, create the prefix and install dotnet 2.0 in one command:

env WINEARCH=win32 WINEPREFIX=~/.wine32 winetricks dotnet20

or only:

env WINEPREFIX=~/.wine32 winetricks dotnet20

if you already set the WINEARCH and created the WINEPREFIX with the 1st command above.