Q161153: HOWTO: Use the Assert Method for Debugging

Article: Q161153
Product(s): Microsoft Visual Basic for Windows
Version(s): 
Operating System(s): 
Keyword(s): kbGrpDSVB
Last Modified: 11-JAN-2001

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The information in this article applies to:

- Microsoft Visual Basic Learning Edition for Windows, version 6.0 
- Microsoft Visual Basic Professional Edition for Windows, version 6.0 
- Microsoft Visual Basic Enterprise Edition for Windows, version 6.0 
- Microsoft Visual Basic Control Creation Edition for Windows, version 5.0 
- Microsoft Visual Basic Enterprise Edition for Windows, version 5.0 
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SUMMARY
=======

The Assert method of the Debug object allows monitoring of an expression for
failure conditions.

MORE INFORMATION
================

The following syntax is used for the Assert method:

  Debug.Assert (expression)

The Assert method syntax has the following object qualifier and part:

     Part            Description
     ----            -----------
     Debug           Required. The Assert method only applies to the
                     Debug object.

     expression      Required. Any logical expression.

The Assert method forces a design-time break at the Assert statement when the
expression evaluates to False. If the expression evaluates as True, program
operation continues. For example:

        Function myFunction (x as Long,y as Long, z as Long) as Long
            Debug.Assert (x<>0 And y<>0 And z<>0)
            myFunction = 1/x + 1/y + 1/z
        End Function

If you call myFunction as:

        q = myFunction (1,2,3)

the program continues as normal. However, passing a zero as any one of the
parameters forces a break. The following example breaks at the Assert
statement:

        q = myFunction (1,0,3)

The above example allows testing for inappropriate parameters to protect against
a division by zero error. If a break occurs at the Assert statement, you can
check the locals window to determine which value is inappropriate. This is
especially useful when the argument values come from other functions:

       q = myFunction ( calcX(), calcY(), calcZ() )

The Assert method is only used for debugging. During compiling, Microsoft Visual
Basic always removes Assert statements from the final code. There is no
workaround for this behavior.

Additional query words: kbVBp500 kbVBp600 kbVBp kbdsd kbDSupport kbNoKeyWord

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Keywords          : kbGrpDSVB 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB600Search kbVBA500Search kbVBA500 kbVBA600 kbVB500 kbVB600 kbZNotKeyword3
Issue type        : kbhowto

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