Visual Basic 2005 in a Nutshell, Third Edition

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Chapter 12: The Language Reference

This is the Title of the Book, eMatter Edition

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See Also

MIRR Function

Is Operator

Syntax

Dim result As Boolean = object1 Is { object2 | Nothing }

object1 (required; Object or any reference type)

An object or instance for comparison

object2 (required; Object or any reference type)

An object or instance for comparison

Description

The Is operator compares two object references and indicates whether they refer to the

same underlying instance (

True) or not (False). It is most often used with If...Then...

Else statements, as in:

If (someVariable Is someOtherVariable) Then

' ----- Equivalent-specific code here.

End If

Comparing a variable with Nothing tests whether an instance has not yet been assigned

to that variable.

If (someVariable Is Nothing) Then

' ----- The variable is undefined.

End If

Usage at a Glance

• Both object1 and object2 must be reference-type variables. This includes string

variables, object variables, and array variables. You can call the

IsReference func-

tion to ensure that both

object1 and object2 are reference types.

• The Is operator can be used with the TypeOf operator to determine if an object

reference is of a specific type.

• The

Is operator reports that uninitialized reference types are equal. For example,

the following comparison equates to

True:

Dim emptyForm As Windows.Forms.Form