Recently, after I updated my Revit 2018 to Revit 2018.3 version, on startup I received following error message:
System.TypeInitializationException: The type initializer for ‘Autodesk.RevitServer.Versioning.Client.HttpClientHelper’ threw an exception. —> System.IO.FileNotFoundException: Could not load file or assembly ‘Autodesk.Bcg.Net, Version=126.96.36.199, Culture=neutral, PublicKeyToken=d672471c03b2c408’ or one of its dependencies. The system cannot find the file specified.
at Autodesk.RevitServer.Versioning.Client. HttpClientHelper..cctor()
— End of inner exception stack trace —
at Autodesk.RevitServer.Versioning.Client. HttpClientHelper.AddProductInformation (String name, String version)
at Autodesk.Revit.UI.Collaborate.CollaborateDBApplication.OnStartup (ControlledApplication application)
at Autodesk.Revit.AddIn. ExternalDBApplicationManager.startupSingleDBApplication (RevitAddInDBApplication dbApplication)
Revit works after I click OK, but the problem was indeed in Revit 2018.3 upgrade. Typical for Autodesk.
The problem and the solution
The problem was in Autodesk Collaboration for Revit 2018 application which was installed on my machine. Since April 2018, there is no more Collaboration for Revit, now it is called BIM 360 Design. Also typical for Autodesk. Let me google that for you.
I do not use Collaboration for Revit so the solution for the problem is to uninstall Autodesk Collaboration for Revit 2018 application.
However, Collaboration for Revit is needed for lower Revit versions (lower than Revit 2018.3). Revit 2018.3 is the only Revit version that will work with both: Collaboration for Revit 2018 and BIM 360 Design. Revit 2019 and newer will work only with BIM 360 Design.