How to set a property of a C# 4 dynamic object when you have the name in another variable
.net, c#, dynamic, reflection
Solution
Not very easily, no. Reflection doesn't work, since it assumes a regular type model, which is not the full range of `dynamic`. If you are actually just talking to regular objects, then just use reflection here. Otherwise, I expect you may want to reverse-engineer the code that the compiler emits for a basic assignment, and tweak it to have a flexibly member-name. I'll be honest, though: this isn't an attractive option; a simple:
dynamic foo = ...
foo.Bar = "abc";
translates to:
if (<Main>o__SiteContainer0.<>p__Site1 == null)
{
<Main>o__SiteContainer0.<>p__Site1 = CallSite<Func<CallSite, object, string, object>>.Create(Binder.SetMember(CSharpBinderFlags.None, "Bar", typeof(Program), new CSharpArgumentInfo[] { CSharpArgumentInfo.Create(CSharpArgumentInfoFlags.None, null), CSharpArgumentInfo.Create(CSharpArgumentInfoFlags.Constant | CSharpArgumentInfoFlags.UseCompileTimeType, null) }));
}
<Main>o__SiteContainer0.<>p__Site1.Target(<Main>o__SiteContainer0.<>p__Site1, foo, "abc");
If you want an approach that works for both dynamic and non-dynamic objects: FastMember is handy for this, and works at either the type or object level:
// could be static or DLR
var wrapped = ObjectAccessor.Create(obj);
string propName = // something known only at runtime
Console.WriteLine(wrapped[propName]);
available on Nuget, and heavily optimised for both dynamic and non-dynamic scenarios.
Problem
I'm looking for a way to modify properties on a `dynamic` C# 4.0 object with the name of the property known only at runtime. Is there a way to do something like (`ExpandoObject` is just used as an example, this could be any class that implements `IDynamicMetaObjectProvider`): ``` string key = "TestKey"; dynamic e = new ExpandoObject(); e[key] = "value"; ``` Which would be equivalent to: ``` dynamic e = new ExpandoObject(); e.TestKey = "value"; ``` Or is the only way forward reflection?