How can I load an older version of a .NET assembly?

Question

I have a WPF/C# application that references .NET 4.0 assemblies. However, within the application is a text editor that needs to display C# intellisense tied to .NET 3.5 asse

Answer 1

I solved this problem using ReflectionOnlyLoadFrom() to load assemblies of whatever version that I need in read-only mode for use with reflection only. When it comes to the fact that you can't do this for mscorlib (you can ask for 2.0, but you'll get 4.0 back from the call), I handled this by filtering the types returned based upon the version that I needed. After all, in this mode, you can only inspect the types in the DLL using reflection, and not really do anything else with them, so you can easily filter the list of types returned as needed.

Here are the types that I've filtered out of mscorlib 4.0 so far so that everything works when an older version of mscorlib is expected:

    /// 

    /// Types to be hidden from .NET mscorlib 4.0 for older versions.
    /// 
    protected static readonly HashSet HideMscorlib4Types = new HashSet
        {
            // The Action delegates with 0, 2, 3, 4 type parameters were moved from System.Core 3.5 to mscorlib for 4.0
            typeof(Action), typeof(Action<,>), typeof(Action<,,>), typeof(Action<,,,>),

            // The Func delegates with 1 to 5 type parameters were moved from System.Core 3.5 to mscorlib for 4.0
            typeof(Func<>), typeof(Func<,>), typeof(Func<,,>), typeof(Func<,,,>), typeof(Func<,,,,>),

            // Other types moved from System.Core 3.5 to mscorlib 4.0
            typeof(TimeZoneInfo),

            // Hide various types that were new in mscorlib 4.0
            typeof(Tuple)
        };