相关疑难解决方法(0)

我有一个类似于下面(MyData类)的对象列表,我将使用LINQ查询来获取那些满足SecondDate属性约束的对象,最后根据所有属性对满足此约束的项进行排序.

public class MyData
{
    public Nullable<DateTime> FirstDate {get; set;}
    public DateTime SecondDate {get; set;}
    public TimeSpan SimpleInterval {get; set;}
    public double SimpleValue {get; set;}
    ...
}

我写了以下查询,但我不知道如何处理该Nullable <DateTime> FirstDate属性.设置为此属性的项null应排序低于具有相同字段值的另一项,但此属性设置为非空值.

// public static void main
double threshold = ... // some initialization
DateTime now = DateTime.Now;
List<MyData> list = new List<MyData>();
...
var items = from item in list
            where ((now - item.SecondDate).TotalSeconds < threshold))
            orderby item.FirstDate descending
            orderby item.SecondDate descending
            orderby …