How to check for NULL Values

Posted on 2005-03-01
Medium Priority
Last Modified: 2012-06-22
What is the best way to check for bull values. I dont want to covert to string if data is null is there a function i can use

cboOriginalCurrency.Value = CType(dtPaymentHeader.Rows(0)(prsgpaymentheader.Columns.vchOriginalCurrency), String)
Question by:anwarmir
LVL 25

Expert Comment

ID: 13429779
isdbnull(object) ? what do you want to do if the value is dbnull
LVL 25

Expert Comment

ID: 13429815
or like

cboOriginalCurrency.Value = iff(isdbnull(dtPaymentHeader.Rows(0)(prsgpaymentheader.Columns.vchOriginalCurrency), "nullvalue",CType(dtPaymentHeader.Rows(0)(prsgpaymentheader.Columns.vchOriginalCurrency), String))


Author Comment

ID: 13430506
id the object is null or empty string then i dont want to do anything....Our standards wont let us use backward compatible functions like IIF
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LVL 25

Expert Comment

ID: 13430527
then just do

if not isdbnull(dtPaymentHeader.Rows(0)(prsgpaymentheader.Columns.vchOriginalCurrency)) then
   cboOriginalCurrency.Value = CType(dtPaymentHeader.Rows(0)(prsgpaymentheader.Columns.vchOriginalCurrency), String)
end if

Author Comment

ID: 13430899
i'm getting isDbNull not declared d o i have to declare it with imports or something?
LVL 28

Accepted Solution

iboutchkine earned 1000 total points
ID: 13431437
fro example you want to check if X is null

if x Is Sytem.DBNull.VAlue then...

Expert Comment

ID: 13472522
i had this same problem this is a function that if the value is null replace it with a certain value based on its data type

Public Function cNull(ByVal objData As Object, ByVal objType As String) As Object
        If IsDBNull(objData) Then
            Select Case objType
                Case "Boolean"
                    Return False
                Case "DateTime"
                    Return DateTime.MinValue
                Case "Decimal", "Double", "Integer", "Long", "Short", "Single"
                    Return 0
                Case "String"
                    Return String.Empty
            End Select
            Return objData
        End If
    End Function

to use the function correctly here is an example

Dim myWidth As Integer= cNull(myDvRow("bldg_width"), "Integer")
Dim myDoor As Double = cNull(myDvRow("door_height"), "Double")
Dim myActive As Boolean = cNull(myDvRow("active_flag"), "Boolean")

etc... i hope this helps also if u put that function in a module u can use it on any form in ur project

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