Programming Visual Basic 2005

Method Arguments

Methods can take any number of parameters.^[*] The parameter list follows the method name and is enclosed in parentheses. Each parameter's type is identified after the name of the parameter.

For example, the following declaration defines a sub named MyMethod that takes two parameters: an Integer and a Button:

Sub MyMethod (firstParam as Integer, secondParam as Button)
  ' ...
End Sub

Within the body of the method, the parameters act as local variables, as if you had declared them in the body of the method and initialized them with the values passed in. Example 18-2 illustrates how you pass values into a method, in this case, values of type Integer and Single.

Example 18-2. Passing parameters

Public Class TestClass
   Sub SomeMethod( _
      ByVal firstParam As Integer, _
      ByVal secondParam As Single)

      Console.WriteLine( _
         "Here are the parameters received: {0}, {1}", _
         firstParam, secondParam)

   End Sub
End Class

Module Module1

   Sub Main()
      Dim howManyPeople As Integer = 5
      Dim pi As Single = 3.14F

      Dim tc As New TestClass()
      tc.SomeMethod(howManyPeople, pi)

   End Sub

End Module

Output:
Here are the parameters received: 5, 3.14

Visual Studio will mark your parameters as ByVal:

               ByVal firstParam As Integer

This indicates that the parameter is passed "by value"—that is, a copy is made.

Tip

Note that, if Strict is On, (which is should be) when you pass in a Single with a decimal part (3.14) you must append the letter f (3.14f) to signal to the compiler that the value is a Single, and not a Double ...