Visual Basic登錄

Question

有人能幫助我我的登錄有問題。 當我嘗試登錄時，出現錯誤「多步OLE DB操作生成錯誤。檢查每個OLE DB狀態值（如果可用），沒有工作完成。」 - 與ExecuteScalar檢索結合。

非常感謝您提供任何幫助，您可能或不可以給我。

Protected Sub btnLogin_Click(sender As Object, e As EventArgs) Handles btnLogin.Click 

    If String.IsNullOrWhiteSpace(txtUsername.Text) Then 
     Invalid() 
     Exit Sub 
    End If 

    Using con As New OleDbConnection(connectionString) 
     Dim cmd As New OleDbCommand("Select count(*) From tblAccounts where Username = ?", con) 
     cmd.Parameters.AddWithValue("Username", txtUsername) 
     con.Open() 

     If CType(cmd.ExecuteScalar(), Integer) > 0 Then 
      cmd.CommandText = "Select CPassword From tblAccounts Where Username = ?" 
      Dim matches As String = CType(cmd.ExecuteScalar(), String) 
      If matches = Sha1(txtPassword.Text) Then 
       Response.Redirect("main.aspx") 
      Else 
       Invalid() 
      End If 
     Else 
      Invalid() 
     End If 
    End Using 

End Sub 

Answer 1

首先，我會建議（已被建議），你重新檢查連接字符串...

就個人而言，我不會再使用相同的OleDbCommand，因爲這可能導致到不希望的結果。相反，我想嘗試類似如下：

Protected Sub btnLogin_Click(sender As Object, e As EventArgs) Handles btnLogin.Click 

    If Not String.IsNullOrWhiteSpace(txtUsername.Text) Then 

     Using con As New OleDbConnection(ConnectionString) 
      con.Open() 

      Dim Result As Integer = 0 

      Using cmd As New OleDbCommand("Select count(*) From tblAccounts where Username = @Username", con) 
       cmd.Parameters.AddWithValue("@Username", txtUsername.text) 

       Result = CInt(cmd.ExecuteScalar) 
      End Using 

      If Result > 0 Then 
       Using cmd As New OleDbCommand("Select CPassword From tblAccounts Where Username = @Username", con) 
        cmd.Parameters.AddWithValue("@Username", txtUsername.text) 

        Dim Obj As Object = cmd.ExecuteScalar() 

        If (Obj IsNot Nothing) AndAlso (Obj IsNot DBNull.Value) Then 
         Dim matches As String = Obj.ToString 

         If matches = SHA1(txtPassword.Text) Then 
          Response.Redirect("main.aspx") 
          Exit Sub 
         End If 

        End If 

       End Using 
      End If 

     End Using 

    End If 

    Invalid() 

End Sub 

希望這有助於