Exception handling

Most methods of the Transaction object throw System.InvalidOperationException if the Transaction is already connected, or Sybase.DataWindow.TransactionException for other failures. You can wrap the Connect, Commit, and Rollback methods in try-catch statements that catch these exceptions.

The TransactionException object has two properties that you can use to help determine the cause of the failure, SqlDbCode and SqlErrorText.

**Table 5-2: TransactionException object properties**
Property	Datatype	Description
SqlDbCode	Int32	Database error code
SqlErrorText	String	The text of the database vendor’s error message corresponding to the error code

Using SqlErrorText and SqlDbCode

The string SqlErrorText in the Transaction object contains the database vendor-supplied error message. The integer named SqlDbCode in the Transaction object contains the database vendor-supplied status code. You can reference these variables in your code.

Example The following try-catch clause handles the exceptions that might be thrown when a Windows application connects to a database, associates a transaction with a DataWindowControl, and retrieves data from the database. Notice that DataWindow operations such as Retrieve might throw a DbErrorException, which also has SqlErrorText and SqlDbCode properties:

[Visual Basic]
Try
   sqlca.Connect()
   dwDept.SetTransaction(sqlca)
   dwDept.Retrieve()
   Dim msg As String
Catch Ex As System.InvalidOperationException
   msg = "The transaction is already connected" _
   + "The application cannot continue"
   MsgBox(msg)
   Application.Exit()
Catch Ex As TransactionException
   msg = Ex.SqlErrorText + _
   "\n\nThe application cannot continue." + _
   "Database Connection Failed"
   Application.Exit()
Catch Ex As DbErrorException
   msg = Ex.SqlErrorText + _
   "\n\nThe application cannot continue." + _
   "DataWindow Operation Failed"
   Application.Exit()
Catch Ex As System.Exception
   msg = Ex.ToString() + _
   "\n\nThe application cannot continue." + _
   "Unexpected Exception"
   Application.Exit()
End Try

[C#]
try 
   {
      sqlca.Connect();
      dwDept.SetTransaction(sqlca);
      dwDept.Retrieve(); 
   } 
   catch (System.InvalidOperationException ex) 
   {
      MessageBox.Show("The application cannot
      continue.", "The transaction is already
      connected", MessageBoxButtons.OK,
      MessageBoxIcon.Stop);
      Application.Exit();
   } 
   catch (TransactionException ex) 
   {
      MessageBox.Show(ex.SqlErrorText + 
      "\n\nThe application cannot continue.", 
      "Database Connection Failed",
      MessageBoxButtons.OK, MessageBoxIcon.Stop);
      Application.Exit();
   } 
   catch (DbErrorException ex) 
   {
      MessageBox.Show(ex.SqlErrorText + 
      "\n\nThe application cannot continue.",
      "DataWindow Operation Failed",
      MessageBoxButtons.OK, MessageBoxIcon.Stop);
      Application.Exit();
   }
   catch (System.Exception ex)
   { 
      MessageBox.Show(ex.ToString() + 
      "\n\nThe application cannot continue.",
      "Unexpected Exception", MessageBoxButtons.OK,
      MessageBoxIcon.Stop);
      Application.Exit();
   }