How can I force .NET to use a local copy of an assembly that's in the GAC

Question

I have a .NET assembly that (for reasons outside my control) must be in the GAC. However, the same assembly is used by another program, which has a its own copy of an older version of the same assembly. It must use its own copy and not whatever is in the GAC. Proper versioning is probably more hassle than it's worth in this case, for reasons I won't go into. My questions is: is there anyway to tell .NET: just use THIS DLL, right here in this directory - ignore whatever you find in the GAC or anywhere else.

Answer 1

Have you tried Assembly.LoadFromFile()? This is a manual thing to do, but should load your assembly into memory before it is needed. .NET will then use the one in memory instead of hunting for it.

Another way would be if the local assembly was unsigned, you could differentiate it that way.

Rob

Answer 2

Make sure the GAC Assembly and local Assembly have different version numbers (not a bad idea to let your build number, at least, auto-increment by wild-carding your AssemblyVersion in AssemblyInfo: [assembly: AssemblyVersion("1.0.0.*")] ). Then, redirect your assembly binding using your app's config:

• http://msdn.microsoft.com/en-us/library/2fc472t2(VS.80).aspx
• http://msdn.microsoft.com/en-us/library/433ysdt1(VS.80).aspx.

In your case, you won't need the "appliesTo" attribute of the assemblyBinding config. You just need something like:

<runtime>
    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
        <dependentAssembly>
            <assemblyIdentity name="YourAssembly" publicKeyToken="AAAAAAAAAAAA" culture="neutral"/>
            <bindingRedirect oldVersion="0.0.0.0-5.2.1.0" newVersion="5.0.8.1"/>
        </dependentAssembly>
    </assemblyBinding>
</runtime>

Answer 3

If they have the same version number the answer is you can't. If you attempt to load an assembly that has the same full assembly name (name, version, key) as a GAC'd assembly the CLR will pick the GAC'd assembly every single time.

Answer 4

You can set the DEVPATH to force load an assembly, see link text

This doesn't answer your question since it only meant for development use and even then not really recommended as it doesn't mirror production usage. However I thought I'll share it anyway since it's good to know.