Exception from Stored Procedure not caught in .NET using SqlDataAdapter.Fill(DataTable) - vb.net

Question

I have a Stored Procedure that I am executing from VB.NET. The SP should insert records into a table and return a set to the calling app. The set returned are the records that were inserted.
If the INSERT fails, the exception is caught and re-thrown in the SP, but I never see the exception in my application. The severity level is 14, so I should see it.
Here is the stored procedure:
BEGIN TRY
BEGIN TRANSACTION
-- Declare local variables
DECLARE #DefaultCategoryID AS BIGINT = 1 -- 1 = 'Default Category' (which means no category)
DECLARE #DefaultWeight AS DECIMAL(18,6) = 0
DECLARE #InsertionDate AS DATETIME2(7) = GETDATE()
DECLARE #SendToWebsite AS BIT = 0 -- 0 = 'NO'
DECLARE #MagentoPartTypeID AS BIGINT = 1 -- For now, this is the only part type we are importing from COPICS ('simple' part type)
DECLARE #NotUploaded_PartStatusID AS TINYINT = 0 -- 0 = 'Not Uploaded'
DECLARE #Enabled_PartStatusID AS TINYINT = 1 -- 1 = 'Enabled'
DECLARE #Disabled_PartStatusID AS TINYINT = 2 -- 2 = 'Disabled'
-- Get the part numbers that will be inserted (this set will be returned to calling procedure).
SELECT c.PartNumber
FROM
COPICSPartFile c
LEFT JOIN Part p on c.PartNumber = p.PartNumber
WHERE
p.PartNumber IS NULL
-- Insert new records from COPICSPartFile (records that don't exist - by PartNumber - in Part table)
INSERT INTO Part
([PartNumber]
,[ReplacementPartNumber]
,[ShortDescription]
,[ListPrice]
,[PartStatusTypeID]
,[Weight]
,[CategoryID]
,[DateInserted]
,[SendToWebsite]
,[FileName]
,[MagentoPartTypeID]
,[PrintNumber])
SELECT
c.PartNumber
,c.ReplacementPartNumber
,c.ShortDescription
,c.ListPrice
,CASE WHEN c.PartStatusTypeID = #Enabled_PartStatusID THEN #NotUploaded_PartStatusID ELSE #Disabled_PartStatusID END
,#DefaultWeight
,#DefaultCategoryID
,#InsertionDate
,#SendToWebsite
,#FileName
,#MagentoPartTypeID
,c.PrintNumber
FROM
COPICSPartFile c
LEFT JOIN Part p on c.PartNumber = p.PartNumber
WHERE
p.PartNumber IS NULL
COMMIT TRANSACTION;
END TRY
BEGIN CATCH
IF ##TRANCOUNT > 0
ROLLBACK TRANSACTION;
THROW;
END CATCH
And here is the .net code:
Try
'Create command
Dim command As New SqlCommand
command.CommandType = CommandType.StoredProcedure
conn = New SqlConnection(m_ConnectionString)
command.Connection = conn
command.CommandText = "trxInsertPartFromCOPICSPartFile"
With command.Parameters
.AddWithValue("#FileName", fileName)
End With
Dim da As New SqlDataAdapter(command)
Dim dt As New DataTable
da.Fill(dt)
If dt.Rows.Count > 0 Then
Return dt
Else
Return Nothing
End If
Catch ex As SqlException
Dim myMessage As String = ex.Message
Finally
If conn.State <> ConnectionState.Closed Then
conn.Close()
End If
End Try
As I was trying to figure out why the exception (duplicate key) wasn't being caught in my application, I tried commenting out the SELECT statement in the SP just before the INSERT and voila. The exception from the INSERT is caught in the application.
Can someone explain to me why the SELECT statement causes this? I know I can break out the SELECT into another SP, but I'd like to keep it all one atomic transaction if possible. Is this expected behavior? Is there a way around it?
Thanks.

Answer 1

The exception is being swallowed by the Fill method. Instead of using that method, create a SqlDataReader, do a command.ExecuteReader(), and then use the reader to populate the DataTable via Load(). This way the error should occur in the ExecuteReader() method and should be catchable. And then you shouldn't need the SqlDataAdapter.
Try
'Create command
Dim command As New SqlCommand
command.CommandType = CommandType.StoredProcedure
conn = New SqlConnection(m_ConnectionString)
command.Connection = conn
command.CommandText = "trxInsertPartFromCOPICSPartFile"
With command.Parameters
.AddWithValue("#FileName", fileName)
End With
Dim dt As New DataTable
conn.Open()
Dim reader As SqlDataReader = command.ExecuteReader()
dt.Load(reader)
If dt.Rows.Count > 0 Then
Return dt
Else
Return Nothing
End If
Catch ex As SqlException
Dim myMessage As String = ex.Message
Finally
If conn.State <> ConnectionState.Closed Then
conn.Close()
End If
End Try
Also, you might be better off on several levels if you combine the SELECT and the INSERT into a single statement. You can do this via the OUTPUT clause, as follows:
INSERT INTO Part
([PartNumber]
,[ReplacementPartNumber]
,[ShortDescription]
,[ListPrice]
,[PartStatusTypeID]
,[Weight]
,[CategoryID]
,[DateInserted]
,[SendToWebsite]
,[FileName]
,[MagentoPartTypeID]
,[PrintNumber])
OUTPUT INSERTED.[PartNumber] -- return the inserted values to the app code
SELECT
c.PartNumber
,c.ReplacementPartNumber
,c.ShortDescription
,c.ListPrice
,CASE WHEN c.PartStatusTypeID = #Enabled_PartStatusID
THEN #NotUploaded_PartStatusID
ELSE #Disabled_PartStatusID END
,#DefaultWeight
,#DefaultCategoryID
,#InsertionDate
,#SendToWebsite
,#FileName
,#MagentoPartTypeID
,c.PrintNumber
FROM
COPICSPartFile c
LEFT JOIN Part p on c.PartNumber = p.PartNumber
WHERE
p.PartNumber IS NULL