January 2006
Beginner
768 pages
32h 25m
English
book
Visual Basic 2005 in a Nutshell, Third Edition
by Tim Patrick, Ron Petrusha, Paul Lomax, Steven Roman PhD
Content preview from 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
Copyright © 2006 O’Reilly & Associates, Inc. All rights reserved.
Syntax
Dim result As Boolean = IsDate(expression)
expression (required; any)
Expression containing a date or time
Description
The IsDate function determines if an expression can be interpreted as a date without
error (
True) or not (False).
Usage at a Glance
• Uninitialized Date variables return True.
• IsDate uses the regional settings of the local system to determine if the value is
recognizable as a date. What is a legal date format on one machine may fail on
another.
See Also
CDate Function
IsDBNull Function
Class
Microsoft.VisualBasic.Information
Syntax
Dim result As Boolean = IsDBNull(expression)
expression (required; any)
The expression to be evaluated against System.DBNull
Description
The IsDBNull function determines whether expression evaluates to System.DbNull
(
True) or not (False).
Usage at a Glance
• DbNull is not the same as Nothing or an empty string. DbNull is used to denote a
missing or nonexistent value, and it is used primarily in the context of database
field values.
• Because of the way that VB deals with expressions containing DBNull, you cannot
simply compare a variable to DBNull, as in:
If (someVariable = DbNull) Then
You must make the comparison using the IsDbNull function.
If (IsDBNull(someVariable) = True) Then
Version Differences
• The
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.