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Editorial Team
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Asked: 2026-05-24T08:34:31+00:00

This is a weird one. I created a new Windows Service in C#, and

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This is a weird one.

I created a new Windows Service in C#, and want to re-use some of the code we created before that’s in a Class Library.

The project is loaded in the solution along with the service. Both target .NET Framework 4.0 (not client profile).

I tried adding a project reference, and it worked for a short while. After working on some old code that I was rewriting, when the project compiled again, it complained that it no longer recognised the namespace for the using statement.

I’ve made sure to clean the solution & rebuild, but no dice. Sometimes VS can have a bad day, so I restarted VS, but this also didn’t work.

I then build the DLL, and add a reference to it via ‘browse’, also no dice. Then I tested it on another project, but after adding it, it works instantly, so it’s not the DLL.

I then checked with other libraries in the solution, but I was able to add a reference to them in the service and access their namespace without a problem.

I’m out of ideas here, anyone got an idea of what to do here?

Thanks,

Nick.

Almoast forgot: the weird thing is, that if I open up the Class view, and expand the ‘References’ section, the namespace/dll doesn’t show up there either… it’s a real conundrom…

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1 Answer

  1. Editorial Team

    I should pay more attention to warnings:

    C:\Windows\Microsoft.NET\Framework\v4.0.30319\Microsoft.Common.targets(1360,9): warning MSB3253: The referenced assembly “” could not be resolved because it has a dependency on “System.Web, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a” which is not in the currently targeted framework “.NETFramework,Version=v4.0,Profile=Client”. Please remove references to assemblies not in the targeted framework or consider retargeting your project.

    So, I’m a ready idiot for checking the DLL’s target framework but not the Windows Service 🙂

    The problem is my DLL uses System.Web, which is not part of the .NET 4 Client Profile framework target. Changing the Service’s Target Framework to 4.0 fixed it.

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