tailieunhanh - Using Visual Basic NET Databases to Create Pricing Trading R_3

Tham khảo tài liệu 'using visual basic net databases to create pricing trading r_3', tài chính - ngân hàng, tài chính doanh nghiệp phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Objects 113 is private and so we will not be able to get or set the value of it from outside the object itself. We can however set the value of strOptionSym through the constructor method known as the New subroutine. So New is called the constructor method. Any time an object is instantiated or born using the New keyword the object s constructor method executes. In this case the public subroutine New accepts a string and sets the value of strOptionSym our private member variable equal to it. By requiring that an option symbol be passed to the constructor method we prevent ourselves or any other programmer using this class from creating a new option object without a symbol. Also notice that we can get the value of strOptionSym through the public property Symbol which has a Get method within it. Public properties provide us with access to private member variables through Get and Set methods. Notice however that our Symbol property is Readonly implying that once the strOptionSym member variable is set via the New method it cannot be changed. Creating a reference type such as an object out of a class is a two-stage process. First we declare the name of the object which will actually then be a variable that holds a reference to the location of the object in memory. Second we create an instance of a class using the New keyword. This is when the constructor method will run. Here is an example of showing the two-stage process Dim myOption As StockOption myOption New StockOption IBMDP Alternatively we can accomplish the process using one line of code Dim myOption As New StockOption IBMDP In different situations it will be advantageous to use one or the other of these two methods. We will use both methods over the course of the book. As with variables it is important to pay close attention to the scope of your reference types which will dictate in many cases the method of instantiation. Team-LRN 114 Introduction to Step 4 In the Forml code window add the following .