Weird behavior when mixing loading of assemblies using Assembly.LoadFrom and Assembly.Load:
I have encountered a weird behavior when loading assemblies with Assembly.LoadFrom and later on with Assembly.Load.
I am loading an assembly using Assembly.LoadFrom, where the assembly is located in a folder, which is not the execution folder.
Later on in my test code when I try to load once again this assembly with Assembly.Load, the load fails with a System.IO.FileNotFoundException (“Could not load file or assembly…”) despite the fact that the assembly is already loaded. The load fails both with the strong name and the non-strong name (the original reason for loading once again this assembly is a usage of a BinaryFormatter).
However, in case the assembly is located in the execution folder the later load succeeds in both cases, with the strong name and the non-strong name. In this case, you can see that two identical assemblies are loaded from two different locations.
A simple code sample that recreates this problem:
Assembly assembly1 = Assembly.LoadFrom(@"C:\a.dll");
// Loading with a strong-name fails
Assembly assembly2 = Assembly.Load(@"a, Version=1.0.0.0, Culture=neutral, PublicKeyToken=14986c3f172d1c2c");
// Also loading with a non-strong fails
Assembly assembly3 = Assembly.Load(@"a");
- Any explanation why the CLR ignores the already loaded assembly?
- Any idea how can I alleviate this problem?
Best Answer
That's not weird. As per the documentation, loading with Load and LoadFrom will place the assemblies in different contexts. This might help.
Because they're in a different context.
Load from the same context, or help the CLR find the assembly, perhaps by attaching a handler to
AppDomain.AssemblyResolve.Alternative
If the location you are loading assemblies from is a subfolder under AppDomain.BaseDirectory you can simply add an entry to your App.config:
http://msdn.microsoft.com/en-us/library/823z9h8w.aspx