Missing compiler required member 'System.Runtime.Compiler...

edited March 2015 in DotNet

Missing compiler required member

I can no longer get the internal VS build (required to allow VS to attach, debug, build) to complete if fails with the following error


Digging deeper I think it is possibly:

Since as someone points out on SO:

"Man I just wasted an hour on this. Thanks for the answer. The dll newtonsoft labels as being for 3.5 is actually not going to work with 3.5. You have to use the dll they label as being for .net 2.0. – Charlie Flowers Oct 15 '10 at 7:07"

for the reasons explained here:


Which is also expanded on http://stackoverflow.com/questions/1102 ... in-net-2-0 and http://devhawk.net/2012/06/20/ambiguous ... te-errors/ and other places.

Is this a known issue. Gah. Will keep digging. :( <-- Yes it is, but this is a 6 years old issue! ??? Now I am confused.

I bought the 100 CCU service fwiw.

Can we get a fix on this? I have ditched the networking for now to work on other things as this had me scratching my head for most of the day . DOH

To be super extra clear, this builds okay in Unity - only VS balks on it.


  • I use the webplayer Target on Unity 4.6.x Windows 7 64 with Visual Studio 2012 and Photon Plus 100CCU cloud.
    Everything latest version from asset store or wherever.

    I have yet to find exactly what situation causes it, will keep trying to play around with settings, targets etc.
    I tried all the "quick fix" workarounds listed above to no avail. Seems like it could probably do with "Fixing" upstream anyways.
  • Maybe the latest 4.6.3p3 helps.

    In our PUN package, the newtonsoft JS dll should only be used in the Editor, not in the Player. Maybe you have another plugin that uses it at runtime? Or maybe Unity includes the dll accidentally.

    Search the project for "Newtonsoft.Json" and make sure it's only once in the project. As said: PUN only needs it in the editor and it could even be ripped out without too much work.

    If StackOverflow suggests to use another Newtonsoft dll, you should do that please. I would do it now but I don't have the project and setup ready to reproduce the issue in the first place, to check if a new/different dll fixes it. When you try, delete the temp and obj folders and any generated solutions to make sure Unity does not keep surplus dlls around somewhere.

    Excuse the late reply and please update us on your progress.
  • ick312
    edited February 2017

    i still have this problem 2 years later.

    i only have newtonsoft once and i have no clue how to solve the issue

    please help
  • AttributeClash
    edited February 2017
    ick312 said:

    i still have this problem 2 years later.

    I downloaded the latest version of Newtonsoft.Json here www.newtonsoft.com/json, took new Newtonsoft.Json.dll from "Net35", replaced Newtonsoft.Json.dll in my project by this and the issue was resolved.