If you are using older version of the .NET Engine, you may need to go through additional steps to get it working in .NET 4.0.
Version 12.5 (and later)
If you are running version 12.5 or later, you do not need to do the below. Starting with version 12.5 Windward no longer uses J#.
Version 10.1 (and later)
Call Report.Init() as your first call to Windward. This will load vjsnativ.dll (using the method described here) and then Windward will run fine under .NET 4.0 (you do not need to load vjsnativ - calling Report.Init will load it).
Version 10.0 (and earlier)
Update: Instead of the below steps, you can add the code described at Calling J# code from .NET 4.0.
Windward is built under .NET 2.0 so that it can be called from any version of .NET. This all works automatically up through .NET 3.5. But for .NET 4.0 and later, there are a couple of additonal steps you must take:
The targeted framework must be set to .NET Framework 4.0, not .NET Framework Client Profile. (This is because we use a couple of calls in the HttpUtility* classes.
Add a reference to vjslib.dll which is in the GAC and at C:\Windows\Microsoft .NET\Framework\v2.0.50727. (This is required for all versions but we add it here for completeness.)
Copy vjsnativ.dll file to the correct location.
For a desktop application, copy the vjsnativ.dll file from C:\Windows\Microsoft .NET\Framework\v2.0.50727 (or C:\Windows\Microsoft .NET\Framework64\v2.0.50727 if your application is 64-bit) to project bin\debug or \release. This file must be located with your program that calls the Windward library when you deploy it too. (The core issue is vjslib.dll cannot find vjsnativ.dll unless it is in the calling program's directory when running under .NET 4.0 - no idea why.)
For a web application deployed through IIS, copy the vjsnativ.dll file from C:\Windows\Microsoft .NET\Framework\v2.0.50727 (or C:\Windows\Microsoft .NET\Framework64\v2.0.50727 if your application is 64-bit) to the same location as w3wp.exe (C:\Windows\System32\inetsrv for 32-bit servers; C:\Windows\SysWOW64\inetsrv for 64-bit servers).
You can find more about this at the J# Developer's Center.