I think you’re confusing the issues of casting and converting here.
- Casting: The act of changing the type of a reference which points to an object. Either moving up or down the object hierarchy or to an implemented interface
- Converting: Creating a new object from the original source object of a different type and accessing it through a reference to that type.
It’s often hard to know the difference between the 2 in C# because both of them use the same C# operator: the cast.
In this situation you are almost certainly not looking for a cast operation. Casting a dynamic
to another dynamic
is essentially an identity conversion. It provides no value because you’re just getting a dynamic
reference back to the same underlying object. The resulting lookup would be no different.
Instead what you appear to want in this scenario is a conversion. That is morphing the underlying object to a different type and accessing the resulting object in a dynamic
fashion. The best API for this is Convert.ChangeType
.
public static dynamic Convert(dynamic source, Type dest) {
return Convert.ChangeType(source, dest);
}
EDIT
The updated question has the following line:
obj definitely implements castTo
If this is the case then the Cast
method doesn’t need to exist. The source object
can simply be assigned to a dynamic
reference.
dynamic d = source;
It sounds like what you’re trying to accomplish is to see a particular interface or type in the hierarchy of source
through a dynamic
reference. That is simply not possible. The resulting dynamic
reference will see the implementation object directly. It doesn’t look through any particular type in the hierarchy of source. So the idea of casting to a different type in the hierarchy and then back to dynamic
is exactly identical to just assigning to dynamic
in the first place. It will still point to the same underlying object.