Is there a way to force all referenced assemblies to be loaded into the app domain?

This seemed to do the trick:

var loadedAssemblies = AppDomain.CurrentDomain.GetAssemblies().ToList();
var loadedPaths = loadedAssemblies.Select(a => a.Location).ToArray();

var referencedPaths = Directory.GetFiles(AppDomain.CurrentDomain.BaseDirectory, "*.dll");
var toLoad = referencedPaths.Where(r => !loadedPaths.Contains(r, StringComparer.InvariantCultureIgnoreCase)).ToList();

toLoad.ForEach(path => loadedAssemblies.Add(AppDomain.CurrentDomain.Load(AssemblyName.GetAssemblyName(path))));

As Jon noted, the ideal solution would need to recurse into the dependencies for each of the loaded assemblies, but in my specific scenario I don't have to worry about it.

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Update: The Managed Extensibility Framework (System.ComponentModel) included in .NET 4 has much better facilities for accomplishing things like this.

You can use Assembly.GetReferencedAssemblies to get an AssemblyName[], and then call Assembly.Load(AssemblyName) on each of them. You'll need to recurse, of course - but preferably keeping track of assemblies you've already loaded :)

just wanted to share a recursive example. I'm calling the LoadReferencedAssembly method in my startup routine like this:

foreach (Assembly assembly in AppDomain.CurrentDomain.GetAssemblies())
{
    this.LoadReferencedAssembly(assembly);
}

This is the recursive method:

private void LoadReferencedAssembly(Assembly assembly)
{
    foreach (AssemblyName name in assembly.GetReferencedAssemblies())
    {
        if (!AppDomain.CurrentDomain.GetAssemblies().Any(a => a.FullName == name.FullName))
        {
            this.LoadReferencedAssembly(Assembly.Load(name));
        }
    }
}