Dynamically adding members to a dynamic object

Question

I\'m looking for a way to add members dynamically to an dynamic object. OK, I guess a little clarification is needed...

When you do that :

dynamic fo         


        

Answer 1

I know this is quite an old post, but I thought I'd pass along Miron Abramson solution on how you can create your own type and add properties at runtime -- in case anyone else out there is looking for something similar.

Answer 2

ExpandoObject implements IDictionary<string,object> albeit explicitly. What this means is that you can simply cast the ExpandoObject to IDictionary<string,object> and manipulate the dictionary.

dynamic foo = new ExpandoObject();
foo.Bar = 42;
food = (IDictionary<string,object>)foo;
food["Baz"] = 54

Answer 3

The opensource framework Dynamitey will do this (available via nuget). It encapsulates while still caching the call site and binder code that @Dino-Viehland used.

Dynamic.InvokeSet(foo,"Bar",42);

It can also call many other kinds of c# binder too.

Answer 4

What you want is similar to Python's getattr/setattr functions. There's no built in equivalent way to do this in C# or VB.NET. The outer layer of the DLR (which ships w/ IronPython and IronRuby in Microsoft.Scripting.dll) includes a set of hosting APIs which includes an ObjectOperations API that has GetMember/SetMember methods. You could use those but you'd need the extra dependency of the DLR and a DLR based language.

Probably the simplest approach would be to create a CallSite w/ one of the existing C# binders. You can get the code for this by looking at the result of "foo.Bar = 42" in ildasm or reflector. But a simple example of this would be:

object x = new ExpandoObject();
CallSite<Func<CallSite, object, object, object>> site = CallSite<Func<CallSite, object, object, object>>.Create(
            Binder.SetMember(
                Microsoft.CSharp.RuntimeBinder.CSharpBinderFlags.None,
                "Foo",
                null,
                new[] { CSharpArgumentInfo.Create(CSharpArgumentInfoFlags.None, null) }
            )
        );
site.Target(site, x, 42);
Console.WriteLine(((dynamic)x).Foo);