A loop in a try..catch

Question

Okay, I have a try..catch such that :

Try   
  Dim dr As OleDbDataReader = performSelect("SELECT * FROM " & table, myConn)
Catch ex As Exception
  sheet = InputBox("Re-enter table:")
  Dim dr As OleDbDataReader = performSelect("SELECT * FROM " & table, myConn)
End Try

The above will only work for the first instance. What I want to do is keep displaying the Input box until the dr is a success (i.e. values have been retrieved from the database.

I know I need some sort of while in the catch, but I am unsure how to proceed

score 2 · Accepted Answer · answered Feb 16 '11 at 20:22

2

Remove the performSelect from inside the catch block, otherwise you could throw an exception there too and it would need to be caught, etc. Put the entire try catch block inside the while loop and exit when you have a value for sheet.

answered Feb 16 '11 at 20:22

JediPotPie

1,068
3
14
21

+1: Seemed like a stupid question.. easy enough. Thanks for the solution. – waqasahmed Feb 16 '11 at 20:31

score 2 · Answer 2 · edited May 23 '17 at 10:24

Have a look here why this is not a good idea.

If you are still interested, you can try this:

   Dim retries As Integer = 3
   While True
       Try
           Dim sheet as String = InputBox("Enter table:")
           Dim dr As OleDbDataReader = performSelect("SELECT * FROM " & sheet, myConn)
           Exit While
       Catch
           retries -= 1
           If retries = 0 Then
               Throw
           Else
               System.Threading.Thread.Sleep(1000)
           End If
       End Try
   End While

Change the retries if you want more(infinite-> <=0), change or remove the thread.sleep if you want to retry immediately.

score 1 · Answer 3 · answered Feb 16 '11 at 20:25

This might work:

    Dim inputOk As Boolean = False

    Do Until inputOk = True
        Try
            Dim dr As OleDbDataReader = performSelect("SELECT * FROM " & table, myConn)
            inputOk = True
        Catch ex As Exception
            sheet = InputBox("Re-enter table:")

        End Try
        End
    Loop

score 0 · Answer 4 · answered Feb 16 '11 at 20:27

0

Catch block has been designed to handle exceptions, not to execute database queries... You should use Jeff's way. The same I was writing, but he's quicker than I

answered Feb 16 '11 at 20:27

Sebastien

80
1
7

A loop in a try..catch

4 Answers4