ACC2000: Trapping Jet Errors with ADO and the OLE DB Provider (201476)

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Microsoft provides programming examples for illustration only, without warranty either expressed or implied. This includes, but is not limited to, the implied warranties of merchantability or fitness for a particular purpose. This article assumes that you are familiar with the programming language that is being demonstrated and with the tools that are used to create and to debug procedures. Microsoft support engineers can help explain the functionality of a particular procedure, but they will not modify these examples to provide added functionality or construct procedures to meet your specific requirements. The sample code in this article uses Microsoft ActiveX Data Objects. For this code to run properly, you need to reference the Microsoft ActiveX Data Objects 2.1 Library.

To demonstrate the example code, follow these steps:

1. Create a new Microsoft Access database.
2. Create a new module.
3. In the new module, type the following code:

   Sub DemonstrateNativeErrors()
      Dim cn As New ADODB.Connection
      On Error GoTo ErrorHandler
   
      ' This code example demonstrates how the Jet OLE DB
      ' provider returns native errors to clients. The
      ' database this code is trying to open should not exist
      ' on the machine in order to produce an error for this demo.
   
      ' The error handler will work for all Jet errors that
      ' are returned to the client, regardless of the
      ' method or SQL statement that caused the error
   
      cn.Provider = "Microsoft.Jet.OLEDB.4.0"
      cn.Open "Data Source=c:\unknown.mdb"
   
      Exit Sub
   
   ErrorHandler:
   
      For i = 0 To cn.Errors.Count - 1
         Debug.Print _
            "Error Source (OLE DB Component Returning Error): " _
            & cn.Errors(i).Source
         Debug.Print "Error Description: " & cn.Errors(i).Description
         Debug.Print "OLE DB Hexadecimal Error Value (HRESULT):" _
            & " 0x" & Hex(cn.Errors(i).Number)
         ' Handle native error:  This functionality is specific to
         ' the native Jet OLE DB provider. Other providers will have
         ' different formats for their native errors, if supported at
         ' all. The native Jet OLE DB provider returns two signed,
         ' 16-bit values in the NativeError value (which is natively a
         ' 32-bit unsigned long). The low word is the major error.
         ' The high word is the minor error. These values are
         ' "sign-descended" to fit into 16 bits and stored together in
         ' the 32-bit unsigned value.
   
         ' These are the errors internally used by Jet and are
         ' different than the errors returned by the Data Access
         ' Object (DAO.) Please see below for how DAO's errors are
         ' exposed. In some cases, Jet has no minor error code for the
         ' particular failure. In these  cases, the major error will
         ' be duplicated into the upper word.
   
         n = cn.Errors(i).NativeError
         Dim uword As Long, lword As Long
   
         If (n < 0) Then
            sign = -1
         Else
            sign = 1
         End If
   
         lword = (Abs(n) And &HFFFF&) * sign
         uword = (Abs((n / 2 ^ 16 - 1)) And &HFFFF&) * sign
         Debug.Print "Minor Error: " & uword
         Debug.Print "Major Error: " & lword
   
         ' The IDA is a string resource value. Multiple Jet errors
         ' may map into a single IDA error. Therefore, the native Jet
         ' errors may provide an additional level of granularity when
         ' writing applications to the native Jet OLE DB provider
   
         Debug.Print "Jet IDA Number (DAO Error): " _
             & cn.Errors(i).SQLState
   
         ' SQLState is actually a SQL92 error reporting construct that
         ' isn't used by the Jet database engine. The DAO values are
         ' provided for backward compatibility with existing and
         ' migrating applications. In general, clients will want to
         ' use internal errors instead of IDA/DAO errors.
   
      Next i
   
      Resume Next
   
   End Sub
   					

4. Press CTRL+G to display the Immediate window.
5. In the Immediate window, type the following and press ENTER:

   DemonstrateNativeErrors
   						

   You next see the following output in the Immediate window.

      Error Source (OLE DB Component Returning Error):
      Microsoft JET Database Engine
      Error Description: Could not find file 'c:\unknown.mdb'.
      OLE DB Hexadecimal Error Value (HRESULT): 0x80004005
      Minor Error: -8158
      Major Error: -1811
      Jet IDA Number (DAO Error): 3024