Mysqldatareader根本不返回记录

Question

我的类中有函数，它获取查询字符串并返回二维对象数组：

 Public Function GetResultsBySql(ByVal sql As String) As Object(,)
        Dim b(,) As Object = Nothing
        Dim Command As New MySqlCommand(sql)
        Dim rowCount As Int32 = -1

        Using Conn As New MySqlConnection(Me.ConnectionString)
            Command.Connection = Conn
            Command.CommandTimeout = TimeOut
            Try
                Conn.Open()
                Dim Dr As MySqlDataReader = Command.ExecuteReader
                Do While Dr.Read
                    rowCount += 1
                    ReDim Preserve b(Dr.FieldCount - 1, rowCount)
                    For j As Int16 = 0 To Dr.FieldCount - 1
                        b(j, rowCount) = Dr(j)
                    Next
                Loop
                Return b
            Catch ex As Exception
                MsgBox(ex.Message.ToString, , "GetResultsBySql")
                Return Nothing
            End Try
        End Using ' Connection 
    End Function

当我提供最初返回156000条记录的查询时。 （在toad for mysql中），对象数组只包含71875条记录。  这是由于DataReader限制还是由于操作内存泄漏？没有异常被抛出。

任何想法？