Question

VB.net Test for Null in Date field

Asked by: Jimbo99999

Good Day

Experts:

How can I test for Null in a Date defined field?  When I look at the newly added Date defined field in Visual Studio Manager it says NULL.  In my VB.net program I want to test for NULL and cannot figure out how to do so.

Thanks,
jimbo99999

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Asked On
2008-09-03 at 06:43:58ID23699133
Topic

Microsoft Visual Basic.Net

Participating Experts
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Answers

 

by: DreamMasterPosted on 2008-09-03 at 07:06:12ID: 22377324

Should be something like
If IsDBNULL(fieldname) Then
'handle this here
Else
'do something else
End If

 

by: VBRocksPosted on 2008-09-03 at 07:06:41ID: 22377327

If myFIeld Is DBNull.Value Then
    '...
End If

 

by: melmersPosted on 2008-09-03 at 07:18:22ID: 22377466

as i know does the NULL keyword or type not exist.
Use instead the Nothing to test against uninitalized data but the
date type is always initalisated.

Which .NET Version do you use

 

by: Jimbo99999Posted on 2008-09-03 at 07:33:31ID: 22377666

I use 2005.

 

by: VBRocksPosted on 2008-09-03 at 07:40:58ID: 22377738

Jimbo9999 - Here is an example of how to do this:

        Dim table As New DataTable()
        table.Columns.Add("MyDate", GetType(Date))
        table.Rows.Add(New Object() {Nothing})


        'Test field for Null
        If table.Rows(0).Item("MyDate") Is DBNull.Value Then
            MsgBox("It is Null")
        Else
            MsgBox("Value is:  " & table.Rows(0).Item("MyDate").ToString())
        End If

 

by: ElrondCTPosted on 2008-09-03 at 07:50:20ID: 22377869

Or, if you're using a strongly typed dataset:

        If drRow.IsMyDateNull Then
            MsgBox("It is Null")
        Else
            MsgBox("Value is:  " & drRow.MyDate.ToString())
        End If

 

by: Jimbo99999Posted on 2008-09-04 at 08:25:31ID: 22388606

Hey There

Thanks for replying everyone.  I am currently trying what VBRocks suggested.  For some reason
I am still not getting NULL evealuated correctly even though I look in the database and the date field on the record says NULL.  So, I step through the program to find that it says there is a value of 12/30/1899 in the field.  

Anyone seen that before?  It is a new one one me.  Not sure what to do now.  Any ideas?

Thanks,
jimbo99999

 

by: ElrondCTPosted on 2008-09-04 at 08:34:48ID: 22388743

What type of database are you using? Access? SQL Server? Excel? How are you "looking in the database"?

 

by: DreamMasterPosted on 2008-09-04 at 23:44:21ID: 22395824

I've seen that before and it simply means you are not getting your date correctly when inserting it in the database. Makes it easier to do a check on it however ;)

Regards,
Max.

 

by: VBRocksPosted on 2008-09-05 at 08:36:56ID: 22400134

Well, you can always use:

        Dim dt As Date = #12/30/1899#
        Date.TryParse(table.Rows(0).Item("MyDate").ToString(), dt)

        If dt = #12/30/1899# Then
            MsgBox("Not valid date")
        Else
            MsgBox("Value is:  " & dt.ToString())
        End If

 

by: Jimbo99999Posted on 2008-09-10 at 11:08:59ID: 31492735

Thanks for the help.

 

by: DreamMasterPosted on 2008-09-10 at 22:50:45ID: 22446653

Glad to have helped. :)

Regards,
Max.

20120131-EE-VQP-002

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