IsAssignableFrom, IsInstanceOfType and the is keyword, what is the difference?

Question

I have an extension method to safe casting objects, that looks like this:

public static T SafeCastAs(this object obj) {
    if (obj == null)
                


        

Answer 1

I guess you're effectively implementing a version of the as operator that works with value types as well as reference types.

I'd go for:

public static T SafeCastAs(this object obj)
{
    return (obj is T) ? (T) obj : default(T);
}

IsAssignableFrom works with types, and is works with instances. They will give you the same results in your case, so you should use the simplest version IMHO.

As for IsInstanceOfType:That is implemented in terms of IsAssignableFrom, so there will be no difference.

You can prove that by using Reflector to look at the definition of IsInstanceOfType():

public virtual bool IsInstanceOfType(object o)
{
    if (o == null)
    {
        return false;
    }
    return this.IsAssignableFrom(o.GetType());
}