Assembly.Load with null Version

[mellinoe]

I'm curious about the behavior of Assembly.Load(AssemblyName) when the given AssemblyName has a null Version property. It seems that, when trying to load an unsigned assembly (no public key), you must assign something to the Version property; even 0.0.0.0 works. For example, the following doesn't work:

Assembly.Load(new AssemblyName("unsigned-assembly"))
>> FileLoadException, "Assembly's manifest definition doesn't match assembly reference"

but the following does. The second one works because the assembly is signed.

Assembly.Load(new AssemblyName("unsigned-assembly") { Version  = new Version(0, 0, 0, 0) });
Assembly.Load(new AssemblyName("signed-assembly"));

Do we have documentation regarding this behavior? It seems a little counter-intuitive to me.

This came up because the latest beta version of xUnit attempts to load assemblies by calling Assembly.Load(new AssemblyName() { Name = ..., Version = null }). Actually it's slightly different than that, but that's the gist of it: https://github.com/xunit/xunit/blob/master/src/common/SerializationHelper.cs#L166.

cc: @jkotas , @nguerrera , @weshaggard

[jkotas]

It looks like a bug to me that we should fix.

[tmat]

We need this to be fixed before we can start running Roslyn tests on CoreCLR.

[sergiy-k]

@kouvel, could you please take a look?

[kouvel]

Sure, I'll take a look

[jkotas]

cc @gkhanna79

[mellinoe]

There was some discussion over email regarding this that wasn't captured here. A main point was that assemblies on the TPA list (everything residing next to CoreRun) must have a version specified in order to be loaded. That seems to be the relevant part of the logic involved here.