Question

I have a set of methods, that take in dates and a bool. These methods then use some SQL then pass it on to another method and return a list. Each method is pretty much the same with the exception of the SQL and the List returned. Now I know there is a better way do these methods but I’m not sure how.

Does anyone have any ideas as to how I can abstract this or use a better design as the methods are almost identical?

Here is the code:

private List<ENT_Message> GetMessageData(DateTime? startDate, DateTime? endDate, bool IsSelectAll)
{
    List<ENT_Message> ret = new List<ENT_Message>();
    string sql = "";

    if (IsSelectAll)
    {
        sql = "select * from tbl_message";
    }
    else
    {
        sql = " Select * from tbl_message where created_Date between @start_Date and @end_date";
    }

    return Converter.SerializeToMessageList(this.GetData(startDate, endDate, IsSelectAll, sql));                   
}

private List<ENT_SensorData> GetSensorData(DateTime? startDate, DateTime? endDate, bool IsSelectAll)
{
    List<ENT_SensorData> ret = new List<ENT_SensorData>();
    string sql = "";

    if (IsSelectAll)
    {
        sql = "select * from tbl_sensor_data";
    }
    else
    {
        sql = "select * from tbl_sensor_data where Timestamp between @start_date and @end_Date";
    }

    return Converter.SerializeToSensorDataList(this.GetData(startDate, endDate, IsSelectAll, sql)); 
}

private List<ENT_SensorDataEvent> GetSensorDataEvents(DateTime? startDate, DateTime? endDate, bool IsSelectAll)
{
    List<ENT_SensorDataEvent> ret = new List<ENT_SensorDataEvent>();
    string sql = "";

    if (IsSelectAll)
    {
        sql = "select * from tbl_sensor_data_event";
    }
    else
    {
        sql = "select * from tbl_sensor_data_event where start_time between @start_date and @end_Date";
    }

    return Converter.SerializeToSensorEventDataList(this.GetData(startDate, endDate, IsSelectAll, sql)); 
}

private List<ENT_SensorDataState> GetSensorDataState(DateTime? startDate, DateTime? endDate, bool IsSelectAll)
{
    List<ENT_SensorDataState> ret = new List<ENT_SensorDataState>();
    string sql = "";

    if (IsSelectAll)
    {
        sql = "select * from tbl_sensor_data_state";
    }
    else
    {
        sql = "select * from tbl_sensor_data_state where start_time between @start_date and @end_Date";
    }

    return Converter.SerializeToSensorDateStateList(this.GetData(startDate, endDate, IsSelectAll, sql)); 
}

private List<ENT_WorkOrder> GetWorkOrders(DateTime? startDate, DateTime? endDate, bool IsSelectAll)
{
    List<ENT_WorkOrder> ret = new List<ENT_WorkOrder>();
    string sql = "";

    if (IsSelectAll)
    {
        sql = "select * from tbl_workorder";
    }
    else
    {
        sql = "select * from tbl_sensor_data_state where completed_date between @start_date and @end_Date";
    }

    return Converter.SerializeToWorkOrderList(this.GetData(startDate, endDate, IsSelectAll, sql));   
}

Answer 1

You could shorten your functions considerably. For example, instead of

private List<ENT_SensorDataState> GetSensorDataState(DateTime? startDate, DateTime? endDate, bool IsSelectAll)
{
    List<ENT_SensorDataState> ret = new List<ENT_SensorDataState>();
    string sql = "";

    if (IsSelectAll)
    {
        sql = "select * from tbl_sensor_data_state";
    }
    else
    {
        sql = "select * from tbl_sensor_data_state where start_time between @start_date and @end_Date";
    }

    return Converter.SerializeToSensorDateStateList(this.GetData(startDate, endDate, IsSelectAll, sql));
}

you could simply write

private List<ENT_SensorDataState> GetSensorDataState(DateTime? startDate, DateTime? endDate, bool IsSelectAll)
{
    string sql = "select * from tbl_sensor_data_state"
                 + (IsSelectAll ? "" : "where start_time between @start_date and @end_Date");

    return Converter.SerializeToSensorDateStateList(this.GetData(startDate, endDate, IsSelectAll, sql));
}

That basically reduces your function to the stuff that really matters: The SQL and the name of the serialization function.