Parameters

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Another way to define variables is through the use of formal method parameters. Table C.1 outlines the four types of method parameters.

Table C.1. Parameter Types in VB.NET

Parameter Type	Modifier	Description
value	ByVal	Modifications do not impact original argument passed into the method
reference	ByRef	Modifications directly impact original argument passed into the method
optional	Optional	Does not require the argument to be supplied; however, a default value must be supplied in the argument declaration
parameter array	ParamArray	Enables variable length parameter lists

Consider the following class that employs each of the parameter types:

  Imports System Class Test     Sub ValueParamMethod(a As Integer)         a =  a + 2 ' the orginal parameter is not modified     End Sub     Sub RefParamMethod(ByRef a As Integer)         a =  a + 2 ' the orginal parameter is not modified     End Sub     Sub OptionalParamMethod(Optional a As Integer = 3)         a =  a + 2 ' if a is not supplied, defaults to 3     End Sub     Sub ParamArrayMethod(ParamArray args As Integer)         ' provides flexibility through indefinite number of arguments     End Sub End Class 

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