Question

I have been looking for a solution to this problem for a while now and am feeling really stuck; I can find solutions to problems that are similar, but not the same as mine.

I am pulling data from a local MSSQL database using a stored procedure, then send the data to a web service. Every part of the component works well except for a pesky problem will a DBNull being returned from the DataRow field, when I know that the field is not null and has valid data. The database and associated INSERT statements that add to this field are designed to not allow NULL entries. When I debug break the program on or right before the line that throws the error I see that the field has valid data for the current row.
If I add a null check to the code (as below) the operation continues as normal:

        Dim dataResultsTable = Me.myViewTableAdapter.GetData(int)

        For Each myDataRow In dataResultsTable.Rows
                        If worker.CancellationPending Then
                            e.Cancel = True
                        Else
                            If myDataRow.Item("syncd") = 0 Then
                               If IsDBNull(myDataRow.Item("bidamount")) Then
                                  _bidAmt = ""
                               Else
    // With out the null check this line throws an error
                                  _bidAmt = myDataRow.Item("bidamount") 
                               End If    

                               If IsDBNull(myDataRow.Item("date_time")) Then
                                  _dateTime = ""
                               Else
    // With out the null check this line throws an error
                                  _dateTime = myDataRow.Item("date_time")
                               End If

// . . . . . . . . 

                               worker.ReportProgress(percentcomplete)
                            End If
                         End If
                      Next

The question here is: Why is the read operation returning DBNull instead of the data in the database? Any and all help here is much appreciated!

EDIT: Just to be clear, the operation does return the proper data, but the data is not being saved into the variable.

Answer 1

This is only a suggestion. In order not to use IsDBNull, why don’t you alter your Stored Procedure by converting default value for Null fields using COALESCE

For example:

SELECT COALESCE(bidamount,''), -- this will convert null value into empty one
       COALESCE(date_time,''), ..... 
FROM .....

as with your code _bidAmt = "" and _dateTime = ""

                    If worker.CancellationPending Then
                        e.Cancel = True
                    Else
                        If myDataRow.Item("syncd") = 0 Then
                              _bidAmt = myDataRow.Item("bidamount")    
                              _dateTime = myDataRow.Item("date_time")
                        End If
                           worker.ReportProgress(percentcomplete)
                        End If
                     End If