Solved

Return Null Nothing for validation purpose

Posted on 2003-12-08
8
264 Views
Last Modified: 2010-05-01
Let say I have the following simple code.
        Dim newStudent

        newStudent = Nothing

        If Not IsNothing(newStudent) Then
            Console.WriteLine("They is something")  <-- This is printed
        Else
            Console.WriteLine("They is nothing")
        End If

I need to do the above so let say when the user enter an invalid data, the fuction will return nothing so that I know the function has detected an error e.g. newStudent = GetStudentDetails() in user input and therefore return nothing so that my calling program will reject the entry.

But the above does not work, even when newStudent is nothing which indicate that they is nothing it still say they is something, help, any alternative method is welcome.
0
Comment
Question by:CplusPlus
  • 4
  • 3
8 Comments
 
LVL 39

Expert Comment

by:appari
ID: 9901890

is this code is in VB.NET?
0
 

Author Comment

by:CplusPlus
ID: 9901898
To appari

Yes. sorry about forgetting,,,
0
 
LVL 39

Expert Comment

by:appari
ID: 9901917
what's the datatype of newStudent?

i have tested with type string, seems to work fine

  Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim x As String
        x = Nothing
        If Not IsNothing(x) Then
            MsgBox("Not Nothing")
        Else
            MsgBox("Nothing")
        End If
        x = "qwqw#"
        If Not IsNothing(x) Then
            MsgBox("Not Nothing")
        Else
            MsgBox("Nothing")
        End If
    End Sub
0
 

Author Comment

by:CplusPlus
ID: 9902066
its actually a struc as in Dim newStudent As Student
 
   Structure Student
        Public Name As String
        Public ID As String
        Public BirthYear As Integer
    End Structure
0
Is Your Active Directory as Secure as You Think?

More than 75% of all records are compromised because of the loss or theft of a privileged credential. Experts have been exploring Active Directory infrastructure to identify key threats and establish best practices for keeping data safe. Attend this month’s webinar to learn more.

 
LVL 49

Expert Comment

by:Ryan Chong
ID: 9902078
Try use the isdbnull function?

If IsDBNull(x) Then
       msgbox "is null"
   Else
       msgbox "not is null"
   End If
0
 

Author Comment

by:CplusPlus
ID: 9902192
does not work ryancys, but thanks anyway.
0
 
LVL 39

Accepted Solution

by:
appari earned 50 total points
ID: 9902207
you can try something like this

      Dim x As student
        x = Nothing
        If Not IsNothing(x.id) Then
            MsgBox("Not Nothing")
        Else
            MsgBox("Nothing")
        End If
0
 

Author Comment

by:CplusPlus
ID: 9902325
Thanks appari, but it seem odd you have to do that to make it work...
0

Featured Post

Is Your Active Directory as Secure as You Think?

More than 75% of all records are compromised because of the loss or theft of a privileged credential. Experts have been exploring Active Directory infrastructure to identify key threats and establish best practices for keeping data safe. Attend this month’s webinar to learn more.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
Runtime error 76: path not found error VB6 program on Windows 7 3 330
using Access 8 59
Question about INSTR  - need to extract data MS ACCESS query 6 54
vbModal 12 35
There are many ways to remove duplicate entries in an SQL or Access database. Most make you temporarily insert an ID field, make a temp table and copy data back and forth, and/or are slow. Here is an easy way in VB6 using ADO to remove duplicate row…
The debugging module of the VB 6 IDE can be accessed by way of the Debug menu item. That menu item can normally be found in the IDE's main menu line as shown in this picture.   There is also a companion Debug Toolbar that looks like the followin…
Get people started with the process of using Access VBA to control Excel using automation, Microsoft Access can control other applications. An example is the ability to programmatically talk to Excel. Using automation, an Access application can laun…
Show developers how to use a criteria form to limit the data that appears on an Access report. It is a common requirement that users can specify the criteria for a report at runtime. The easiest way to accomplish this is using a criteria form that a…

920 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

16 Experts available now in Live!

Get 1:1 Help Now