余小章 @ 大內殿堂

1.ADO.NET提供了相關的例外 DbException 類別 供開發者使用，建議在寫相關資料庫的時候可以把它擺上去，補捉到的錯誤訊息會比較詳細。

2.繼承 DbException 類別 的有以下。

System.Data.Odbc.OdbcException
System.Data.OleDb.OleDbException
System.Data.OracleClient.OracleException
System.Data.SqlClient.SqlException

3.記得要將 DbException 擺在 Exception 之前

Try
'實作內容
Catch dbex As OleDbException
'例外捕捉
Catch ex As Exception
'例外捕捉 
End Try 

  
    Try
        Using cn As New OleDbConnection(cs)
            Dim qs As String = "SELECT * FROM Employees;"
            If cn.State = ConnectionState.Closed Then
                cn.Open()
            End If 
            Using cmd As New OleDbCommand(qs, cn)
                Using dr As OleDbDataReader = cmd.ExecuteReader()
                    Dim dt As New DataTable()
                    dt.Load(dr)
                    Me.DataGridView1.DataSource = dt
                End Using
            End Using 
        End Using
    Catch dbex As OleDbException
        Console.WriteLine(OleExInfo(dbex))
        MessageBox.Show(OleExInfo(dbex), "例外發生", MessageBoxButtons.OK, MessageBoxIcon.Error)
    Catch ex As Exception
        MessageBox.Show(OleExInfo(ex), "例外發生", MessageBoxButtons.OK, MessageBoxIcon.Error)
    End Try
End Sub
Private Function OleExInfo(ByVal ex As OleDbException) As String
    Dim ErrInfo As String = ""
    For i As Integer = 0 To ex.Errors.Count - 1
        ErrInfo = "索引: " & i.ToString
        ErrInfo &= ControlChars.NewLine
        ErrInfo &= "錯誤說明: " & ex.Errors(i).Message
        ErrInfo &= ControlChars.NewLine
        ErrInfo &= "資料庫錯誤: " & ex.Errors(i).NativeError
        ErrInfo &= ControlChars.NewLine
        ErrInfo &= "提供者名稱: " & ex.Errors(i).Source
        ErrInfo &= ControlChars.NewLine
        ErrInfo &= "錯誤代碼:" & ex.Errors(i).SQLState
        ErrInfo &= ControlChars.NewLine
    Next i
    Return ErrInfo
End Function
Private Function SysExInfo(ByVal ex As Exception) As String
    Dim ErrInfo As String = ""
    ErrInfo = "Source : " & ex.Source
    ErrInfo &= ControlChars.NewLine
    ErrInfo &= "Data : " & ex.Data.ToString
    ErrInfo &= ControlChars.NewLine
    ErrInfo &= "Exception Message : " & ex.Message
    Console.WriteLine("Database Exception" & ErrInfo)
    Return ErrInfo
End Function 
  
  
 
 
 
 
  
5.在MSDN下找不到這兩個類別相關的資訊，所以我認為這兩個類別是獨立不同的，但我試著用 System.Exception 類別丟到 OLEDbException 類別程式卻可以執行，反之亦可；可見這兩個類別有繼承相同的東西。知道的人可以告知一下小弟嗎
  
Catch dbex As OleDbException
    MessageBox.Show(SysExInfo(dbex), "例外發生", MessageBoxButtons.OK, MessageBoxIcon.Error)
Catch ex As Exception
    MessageBox.Show(OleExInfo(ex), "例外發生", MessageBoxButtons.OK, MessageBoxIcon.Error)
End Try

6.原來將 滑鼠游標停在 OleDbException 類別，按f12就可以知道彼此的繼承關係了
vb直接按f12，就會出現"物件瀏覽器"，如下圖 
  
 
 
c#比較麻煩一點
要先對OleDbException按一次F12，再對DbException再按一次F12(如下圖)
下圖就能看到彼此的關係
6.範例下載：
VB_DBException.rar
  
CS_DBException.rar
  
 
                    
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Microsoft MVP Award 2010~2017 C# 第四季
Microsoft MVP Award 2018~2022 .NET