Linq 基本語法 – OrderBy 與 OrderByDescending

這兩個使用方式都相當簡單

OrderBy:
The OrderBy operator allows an input sequence to be ordered based on a keySelector method that will return a key value for each input element, and an ordered output sequence, IOrderedEnumerable<T>, will be yielded in ascending order based on the values of the returned keys.

若繼續範例中的那個字串陣列

var nameObjs = presidents.OrderBy(s=>s);

StringBuilder sb = new StringBuilder();

foreach (var item in nameObjs)

{

  sb.AppendLine(item);                

}

richTextBox1.Text = sb.ToString();

可以得到如下結果:
 

OrderByDescending:
This operator is prototyped and behaves just like the OrderBy operator, except that it orders in descending order.

從上面的字義，可以很清楚了解到
其實OrderByDescending是降冪排序
而OrderBy是升冪排序

var nameObjs = presidents.OrderByDescending(s=>s);

StringBuilder sb = new StringBuilder();

foreach (var item in nameObjs)

{

  sb.AppendLine(item);                

}

richTextBox1.Text = sb.ToString();

最後產生如下結果: