I have a reference to System.Data in my windows service project. I keep getting the Exception :
Could not load file or assembly 'System.Data, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' or one of its dependencies. The system cannot find the file specified.
I attach the FusionLog to my code and found out the following. For System.Data only visual studio is looking here:
Assembly manager loaded from: C:\windows\Microsoft.NET\Framework\v2.0.50727\mscorwks.dll
And it should be looking here (all the other assemblies are but System.Data)
Assembly manager loaded from: C:\windows\Microsoft.NET\Framework\v4.0.30319\clr.dll
How can I do point my System.Data file to look in the right place?
My guess is Microsoft Commerce Server dlls are referenceing the 2.0 folder maybe.
Add this to app.config..
<startup useLegacyV2RuntimeActivationPolicy="true">
<supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0" />
</startup>
If you need old versions of dlls to be loaded in a windows service you must add this. For web services iis automatically takes care of it, but not for windows service.
Make sure your project is set to .Net Framework 4. If that doesn't do it, set it to full profile (not just Client)
If you select the referenced assembly in the solution explorer, verify that the runtime version is correct (see image below). You can remove the reference and re-add it to fix it if necessary.
Also, if you are using an app.config, make sure it is targeting the correct runtime version.
来源：https://stackoverflow.com/questions/10641958/system-data-assembly-not-found