How can attach to AppDomain.CurrentDomain.AssemblyResolve in a DLL

Question

I have a dll that other applications use. It relies on a 3rd party dll that updates fairly regularly. As long as the version I need or greater is present then I am happy.

But Visual Studio forces the exact version I need on the apps that use my dll.

I want to add an event handler to AppDomain.CurrentDomain.AssemblyResolve so I can check for a later version and just use that. But I don't know where to add it.

Most apps would put this in program.cs startup. But a dll does not have that.

I would put it in a static constructor, but I have many classes that use this 3rd party dll. It seems messy to put this event attach into each class.

Is there any other option?

Is the 3rd party DLL managed or unmanaged? From the question I assume managed. — Chris Shain, Aug 24 '12 at 17:38
Alternatively, use a profiler with time stamps to see what tends to get hit first. If will be tough though for a very disjointed library. — leppie, Aug 24 '12 at 17:42
@Chris Shain - Both mine and the 3rd party libraries are managed. — Vaccano, Aug 24 '12 at 17:44
@leppie - But then I have to enforce my config options on the users of my DLL. — Vaccano, Aug 24 '12 at 17:44
@leppie - the dll's classes can be used in part or in full. It is mostly a collection of helper classes. Sot it just depends on the apps as to which one is used first. — Vaccano, Aug 24 '12 at 17:45

Peter Ritchie · Answer 1 · 2012-08-24T18:07:42.583

1

Ben Hall has an example of doing this http://blog.benhall.me.uk/2006/08/appdomaincurrentdomainassemblyresolve.html:

private Assembly AssemblyResolveHandler(object sender,ResolveEventArgs e)
{
    try
    {
        string[] assemblyDetail = e.Name.Split(',');
        string assemblyBasePath = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location);
        Assembly assembly = Assembly.LoadFrom(assemblyBasePath + @"\" + assemblyDetail[0] + ".dll");
        return assembly;
    }
    catch (Exception ex)
    {
        throw new ApplicationException("Failed resolving assembly", ex);
    }
}

Make sure the assignment of the delegate to AssemblyResolve is done before you try to resolve the types you want to "redirect". http://msdn.microsoft.com/en-us/library/system.appdomain.assemblyresolve.aspx shows and example of this.

edited Aug 24 '12 at 18:07

answered Aug 24 '12 at 17:44

Peter Ritchie

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Yes, but where do I attach to this? A dll has no OnLoad method to let me get this attached before the failure happens. (That is the point of the question.) – Vaccano Aug 24 '12 at 17:52
In terms of a dll, that dll would have to be loaded *before* the types you want to redirect are loaded. Without doing *that* in Main(), there's no way to guarantee that. At which point, you're basically forced to do the event subscription in main. – Peter Ritchie Aug 24 '12 at 18:10

score 1 · Answer 2 · answered Aug 24 '12 at 17:44

1

Can you use assembly binding redirect?

<configuration>
    <runtime>
        <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
            <dependentAssembly>
                <assemblyIdentity name="Foo.Bar" publicKeyToken="***" culture="neutral"/>
                <bindingRedirect oldVersion="0.0.0.0-2.0.0.0" newVersion="2.0.0.1"/>
            </dependentAssembly>
        </assemblyBinding>
    </runtime>
</configuration>

answered Aug 24 '12 at 17:44

oleksii

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This is the best solution. I don't like it because it forces the apps that use my dll to deal with the fact that I don't have the same version as they do (I would like my code to not cause any headaches for those who forget to do this). – Vaccano Aug 24 '12 at 17:53

How can attach to AppDomain.CurrentDomain.AssemblyResolve in a DLL

2 Answers2