Question

This is a pretty general question, but the specific thing I’m doing is simple so I’m including the code. How do I check for type compatibility between two objects when I don’t know the type of either at compile time?

That is, I can do if (object is SomeType) when SomeType is a type name known at compile time. GetType() is not sufficient because it will not work with derived types. Basically I want to be able to say, if (object.IsTypeOfOrIsDerivedFrom(someType)) where sig of this magical method is IsTypeOfOrIsDerivedFrom(Type type)

Here is the context.

// Return all controls that are (or are derived from) any of a list of Types
public static IEnumerable<Control> FindControls(this Control control, IEnumerable<Type> types, bool recurse) 
{
    foreach (Control ctl in control.Controls)
    {
        /// How can I compare the base types of item & ctl?
        if (types.Any(item=>  .... ))
        {
            yield return (ctl);
        }
        if (recurse && ctl.Controls.Count > 0)
        {
            IEnumerable<Control> subCtl = ctl.FindControls(types,true);
            if (subCtl != null)
            {
                yield return (subCtl);
            }
        }
    }
    yield break;
}

Answer 1

You can use, Type.IsAssignableFrom e.g.

public class Foo { }

public class Bar : Foo { }

...

bool compatible = typeof(Foo).IsAssignableFrom(typeof(Bar));