.net - Found conflicts between different versions of the same dependent assembly that could not be resolved

Question

When I clean and then build my solution that has several projects, the output window reports that the build succeeded. However, when I view the Error List Window, it shows me this warning:

Found conflicts between different versions of the same dependent assembly that could not be resolved. These reference conflicts are listed in the build log when log verbosity is set to detailed. C:Program Files (x86)MSBuild12.0inMicrosoft.Common.CurrentVersion.targets

When I double-click this message, it opens the C:Program Files (x86)MSBuild12.0inMicrosoft.Common.CurrentVersion.targets file but I don't understand anything in it.

I am using Visual Studio Express 2013 for the Web.

How do I find out what's wrong and with which DLL and how do I then make the warning go away?

Answer 1

eta: There's a killer article on this stuff by SO's own @Nick Craver that you should read

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While the other responses say this, they don't make it explicit, so I will....

On VS2013.2, to actually trigger the emission of the cited information, you need to not read the message, which says:

C:Program Files (x86)MSBuild12.0inMicrosoft.Common.CurrentVersion.targets(1697,5): warning MSB3277: Found conflicts between different versions of the same dependent assembly that could not be resolved. These reference conflicts are listed in the build log when log verbosity is set to detailed.

This is incorrect (or at least it was for some versions of Visual Studio - it seems to be OK on an up to date VS2015 Update 3 or later). Instead turn it to Diagnostic (from Tools->Options->Project and Solutions->Build and Run, set MSBuild project build output verbosity), whereupon you'll see messages such as:

There was a conflict between "Newtonsoft.Json, Version=6.0.0.0, Culture=neutral, PublicKeyToken=30ad4fe6b2a6aeed" and "Newtonsoft.Json, Version=6.0.5.17707, Culture=neutral, PublicKeyToken=30ad4fe6b2a6aeed".

• "Newtonsoft.Json, Version=6.0.0.0, Culture=neutral, PublicKeyToken=30ad4fe6b2a6aeed" was chosen because it was primary and "Newtonsoft.Json, Version=6.0.5.17707, Culture=neutral, PublicKeyToken=30ad4fe6b2a6aeed" was not.

Then

• Ctrl-Alt-O to go to Build output window
• search for "was chosen" to find the drilldown.

...And yes, for those looking at the detail of the [diagnostic] message, it was news to this ignoramus that there's a convention in town whereby all 6.x versions are, internally Assembly Version 6.0.0.0, i.e. only the SemVer Major component goes into the Assembly Version :)