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In the MSDN documentation for the AppDomain.CreateInstanceAndUnwrap method, it states as a note

If you make an early-bound call to a method M of an object of type T1 that was returned by CreateInstanceAndUnwrap, and that method makes an early-bound call to a method of an object of type T2 in an assembly C other than the current assembly or the assembly containing T1, assembly C is loaded into the current application domain. This loading occurs even if the early-bound call to T1.M() was made in the body of a DynamicMethod, or in other dynamically generated code. If the current domain is the default domain, assembly C cannot be unloaded until the process ends. If the current domain later attempts to load assembly C, the load might fail.

(http://msdn.microsoft.com/en-us/library/3c4f1xde.aspx)

Does anyone have a technical explanation for the above note? Why is this the case? Is Assembly dependency lookup done when a method is first called on the object?

Calvin Grunewald
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1 Answers1

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Assembly dependency is call when you're creating instance of the object.

Let's analyze hypothetical scenario. We have 2 DLLs: Lib1 and Lib2. (Lib1 uses methods from Lib2).

In our application main method looks as below:

Worker localWorker = new Worker();
localWorker.PrintDomain();

AppDomain ad = AppDomain.CreateDomain("New domain");
Worker remoteWorker = (Worker)ad.CreateInstanceAndUnwrap("Lib1","Lib1.Worker");
remoteWorker.PrintDomain();

Assembly dependency is checking in line: 

Worker remoteWorker = (Worker)ad.CreateInstanceAndUnwrap("Lib1","Lib1.Worker");

For example if the Lib2.dll doesn't exist we'll get an exception.

Łukasz
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