DirectCast, MyBase keywords

DirectCast converts an expression (first argument) to a given type (second argument) in the same way as CType does.

However, DirectCast only works if the run time type of the expression is the same as the type it's being cast to or if it inherits from or implements that type. In constrast, CType works if there is any kind of conversion defined between the two types, even if it doesn't involve inheritance (for example Integer to Long).

Because DirectCast is stricter than CType, it works faster. 

When coding instance members of a class, MyBase can be used to refer to the base class of that class. It is most commonly used to call the base class constructor (MyBase.New) or to access base class members that are hidden by current class members of the same name.