Programmatically modify Assembly Binding

Question

I have an issue working with Microsoft.Build.BuildEngine which supposed to get fixed modifing my .exe.config file to add the following.

<?xml version ="1.0"?>
<configuration>
        <runtime>
           <assemblyBinding xmlns="urnchemas-microsoft-com:asm.v1">
            <dependentAssembly>
                <assemblyIdentity name="Microsoft.Build.Framework" publicKeyToken="b03f5f7f11d50a3a" culture="neutral"/>
                <bindingRedirect oldVersion="0.0.0.0-99.9.9.9" newVersion="3.5.0.0"/>
            </dependentAssembly>
                <assemblyIdentity name="Microsoft.Build.Engine" publicKeyToken="b03f5f7f11d50a3a" culture="neutral"/>
                <bindingRedirect oldVersion="0.0.0.0-99.9.9.9" newVersion="3.5.0.0"/>
            </dependentAssembly>
        </assemblyBinding>
    </runtime>
</configuration>

My problem is, I can't modify the file, I have to fix it by code, and I think that's supposed to be possible, right?

But how?, how can I modify my application so it runs as if the above changes were made on the config file?

Answer 1

One way of doing it is to create a bootstrapping app which when launched would start your original app in a separate appdomain. When you set up the new domain you will be able to build the config file programmatically.

Answer 2

I was just struggling with a similar problem. The key is to use the AppDomain.AssemblyResolve event. Here's what my code looks like:

    public void LoadStuff(string assemblyFile)
    {
        AppDomain.CurrentDomain.AssemblyResolve += 
            new ResolveEventHandler(CurrentDomain_AssemblyResolve);
        var assembly = Assembly.LoadFrom(assemblyFile);

        // Now load a bunch of types from the assembly...
    }

    Assembly CurrentDomain_AssemblyResolve(object sender, ResolveEventArgs args)
    {
        var name = new AssemblyName(args.Name);
        if (name.Name == "FooLibrary")
        {
            return typeof(FooClass).Assembly;
        }
        return null;
    }

This completely ignores the version number and substitutes the already loaded library for any library reference named "FooLibrary". You can use the other attributes of the AssemblyName class if you want to be more restrictive. FooClass can be any class in the FooLibrary assembly.