While making some changes to an existing BizTalk Server project, I was continuously getting a strange error saying that I couldn’t reference a clrtypes.dll. To be more precise, it couldn’t reference the name-of-my-project.clrtypes.dll
Severity Code Description Project File Line Suppression State
Error error referencing assembly ‘obj\debug\application.common.processing.clrtypes.dll‘ obj\debug\application.common.processing.processing.clrtypes.dll 2
Strangely, this only happens on the projects that have orchestrations.
Cause
The real cause of this issue is somewhat difficult to explain, as it doesn’t always occur. However, I know for a fact that I do not create any clrtypes.dll files. What happens is that when Visual Studio compiles the project, it will make a temporary build output (obj\Debug\)
The obj folder is recreated during builds, so references to it often break mid-build — especially with BizTalk orchestrations, which require all referenced assemblies to be fully compiled and stable before the orchestration compiler runs.
Solution
The solution to this issue is quite simple:
- Access the project folder in File Explorer.
- And delete the obj folder.
Now, if you try to compile again, it may give different errors, but that .clrtypes.dll will be “fixed”
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