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Editorial Team
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Asked: 2026-06-10T01:42:39+00:00

Why is it that when a .NET DLL is loaded, replaced from another app

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Why is it that when a .NET DLL is loaded, replaced from another app domain (DLL is updated with a new version), and then reloaded (using Assembly.LoadFrom) that the version info still reflects the old version?

The same is observed with assembly.GetCustomAttributes(typeof(AssemblyFileVersionAttribute), false) or assembly.GetCustomAttributes(typeof(AssemblyVersionAttribute), false).

Is this the normal behavior? If I inspect the file in Explorer, I see the correct version, though.

Is there any way to get the actual version of the DLL?

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1 Answer

  1. Editorial Team

    It isn’t very clear, but the term “re-loaded” is a strong indicator for what you see. The CLR will not permit reloading a different version of the same assembly with Assembly.LoadFrom(). This is a strong DLL Hell counter measure and avoids a lot of nasty runtime exceptions. In particular InvalidCastExceptions that say “Cannot cast Foo to Foo”. Type identity in .NET includes the [AssemblyVersion] of an assembly. Calling Assembly.LoadFrom() will just return a reference to the previously loaded assembly.

    Nor is there a way to unload an assembly from an AppDomain. Only thing you can do is create a new AppDomain.

    I should not mention Assembly.LoadFile(), it doesn’t perform this check, that’s major misery.

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