IsDBNull function

[zozzie]

Hi guys,

Is there anybody who can help me with the IsDBNull function. I would like to use it to check if the field "CompanyID" in the datatable "tblCD" is a DBNull value.

If IsDBNull(Me.DSlistboxes.Tables("tblCD").Rows(0)("CompanyID")) Then
            CompanyIDEmpty = True
        Else
            CompanyIDEmpty = False
        End If

I'm sure the row(0) contains a DBNull-value (I inserted it myself) but the function IsDBNull doesn't detect it because the boolean CompanyEmptyID is always false while it should be true for that row.

What am I doing wrong? Or is there another way to check for dbnull values?

Kind regards,

Tom

[RichardAtherton]

don't understand here is my own working code:

Dim cn1 As OledbConnection = New OledbConnection(DbNam)
Dim Oledbstr As String = "Select CompanyName,Address1,Address2,Address3,Address4,StationeryChoice from SystemValues where SysVal = 1"
Dim Cmd1 As OledbCommand = New OledbCommand(Oledbstr, cn1)
cn1.Open()
Dim dr1 As OledbDataReader = Cmd1.ExecuteReader()
dr1.Read()

If Not IsDBNull(dr1("CompanyName")) Then
dv1.Value = dr1("CompanyName")
Else
dv1.Value = " "
End If

looks very much like your own.

[zozzie]

Hi Richard,

thanks for your reply. I tried your code (adapted to my situation)

Dim Oledbstr As String
        Oledbstr = "SELECT * FROM tblCD WHERE CDID=1"
        Dim Cmd1 As OleDbCommand = New OleDbCommand(Oledbstr, DataConnection)
        DataConnection.Open()
        Dim dr1 As OleDbDataReader = Cmd1.ExecuteReader()
        dr1.Read()
 
        If Not IsDBNull(dr1("CompanyID")) Then
            CompanyIDEmpty = False
        Else
            CompanyIDEmpty = True
        End If

but it gives the same results: DBNull isn't detected.

Any ideas??

tom

[hellswraith]

If Me.DSlistboxes.Tables("tblCD").Rows(0)("CompanyID") Is DbNull.Value Then
            CompanyIDEmpty = True
        Else
            CompanyIDEmpty = False
        End If

[RichardAtherton]

? well I've run out of ideas can't see anything wrong

[zozzie]

Thanks for the replies.

I set the DbNull value as follows:

DSlistboxes.Tables("tblCD").Rows(Me.BindingContext(DSlistboxes, "tblCD").Position)("CompanyID") = System.DBNull.Value

I tried the code of hellswraith, but it also doesn't detect the dnull value. I'm getting hopeless here. I use an access database (access 2000)

any ideas???

thanks,

tom