ThenBy、ThenByDescending、OrderBy、OrderByDescending 的用法

 

以下範例示範了 ThenBy、ThenByDescending、OrderBy、OrderByDescending 四種用法

// 建立訂單資料來源
var orders = new List<Order>(){
        new Order {CustomerId = 3, OrderDate = new DateTime(2011, 10, 9), Total = 2940},
        new Order {CustomerId = 2, OrderDate = new DateTime(2012, 10, 10), Total = 3849},
        new Order {CustomerId = 1, OrderDate = new DateTime(2011, 12, 1), Total = 500},
        new Order {CustomerId = 1, OrderDate = new DateTime(2012, 2, 28), Total = 1234},
        new Order {CustomerId = 2, OrderDate = new DateTime(2012, 5, 20), Total = 9520}
};

Console.WriteLine("原排序");
foreach (var e in orders)
    Console.WriteLine(e.ToString());
Console.WriteLine();

// 1、遞增排序
Console.WriteLine("遞增排序");
var singleOrderAsc = orders.OrderBy(e => e.CustomerId);
foreach (var e in singleOrderAsc)
    Console.WriteLine(e.ToString());
Console.WriteLine();

// 2、遞減排序
Console.WriteLine("遞減排序");
var singleOrderDesc = singleOrderAsc.OrderByDescending(e => e.CustomerId);
foreach (var e in singleOrderDesc)
    Console.WriteLine(e.ToString());
Console.WriteLine();

// 3、多欄位遞減排序
Console.WriteLine("多欄位遞減排序");
var OrderDesc = singleOrderAsc
    .OrderByDescending(e => e.CustomerId)
    .ThenByDescending(e => e.Total);
foreach (var e in OrderDesc)
    Console.WriteLine(e.ToString());
Console.WriteLine();

// 4、多欄位之先遞減再遞增排序
Console.WriteLine("多欄位之先遞減再遞增排序");
var OrderDescAsc = OrderDesc
    .OrderByDescending(e => e.CustomerId)
    .ThenBy(e => e.Total);
foreach (var e in OrderDescAsc)
    Console.WriteLine(e.ToString());
Console.WriteLine();

//訂單基本資料類別
public class Order
{
    public int CustomerId { get; set; }
    public DateTime OrderDate { get; set; }
    public double Total { get; set; }

    public override string ToString()
    {
        return string.Format("CustomerId = {0}, OrderDate = {1}, Total = {2}",
                                CustomerId, OrderDate, Total);
    }
}

參考資料：
LINQ自學筆記-語法應用-資料排序-OrderBy、ThenBy 和遞減