How Does Resharper Know “Expression is always true”?

Question

Check out the following code:

private void Foo(object bar)
{
   Type type = bar.GetType();

    if (type != null) // Expression is always true
    {   
    }         


        

Answer 1

object.GetType is not virtual, so you cannot yourself implement a version that returns a null value. Therefore, if bar is null, you will get a NullReferenceException and otherwise, type will never by null.