Programming Visual Basic .NET, Second Edition

Branching

Visual Basic .NET statements are evaluated in order. The compiler starts at the beginning of a statement list and makes its way to the bottom. This would be entirely straightforward, and terribly limiting, were it not for branching. There are two types of branches in a Visual Basic .NET program: unconditional branching and conditional branching .

Program flow is also affected by looping and iteration statements, which are signaled by the keywords If, Select Case, For, Do, While, and For Each. Iteration is discussed later in this chapter, and For Each is considered in Chapter 3. For now, let’s consider some of the more basic methods of conditional and unconditional branching.

Unconditional Branching Statements

An unconditional branch is created by invoking a method. When the compiler encounters the name of a method it stops execution in the current method and branches to the newly “called” method. When that method returns a value, execution picks up in the original method on the line just below the method call. Example 3-4 illustrates.

Example 3-4. Calling a method

Option Strict On
Imports System
Module Module1
   Sub Main( )
      Console.WriteLine("In Main! Calling SomeMethod( )...")
      SomeMethod( )
      Console.WriteLine("Back in Main( ).")
   End Sub 'Main

   Sub SomeMethod( )
      Console.WriteLine("Greetings from SomeMethod!")
   End Sub 'SomeMethod

End Module

Output:
In Main! Calling SomeMethod( )...
Greetings from SomeMethod!
Back in Main( ).

Program flow begins in Main( ) and proceeds until ...