C#LINQ用有意义的字符串替换空值

Question

从列表中

class Delivery
{
    public string ProductCode
    {
        get;
        set;
    }

    public DateTime? OrderedDate
    {
        get;
        set;
    }

    public DateTime? DeliveryDate
    {
        get;
        set;
    }

    public Delivery(string pcode, DateTime? orddate, DateTime? deldate)
    {
        ProductCode = pcode;
        OrderedDate = orddate;
        DeliveryDate = deldate;
    }
}


List<Delivery> DeliveryList = new List<Delivery>();
DeliveryList.Add(new Delivery("P001",new DateTime(2009,01,27),null));
DeliveryList.Add(new Delivery("P007",new DateTime(2009,05,17),null));
DeliveryList.Add(new Delivery("P031", new DateTime(2008, 03, 15),
new DateTime(2008,04 ,22)));
DeliveryList.Add(new Delivery("P011",new DateTime(2009,01,27),
new DateTime(2009,02,12)));
DeliveryList.Add(new Delivery("P041",new DateTime(2009,01,27),null));
DeliveryList.Add(new Delivery("P051", new DateTime(2009, 01, 27),
new DateTime(2009, 02, 12)));
DeliveryList.Add(new Delivery("P501",new DateTime(2009,01,27),null));
DeliveryList.Add(new Delivery("P801",new DateTime(2009,01,27),null));

var query = DeliveryList.OrderBy(p => p.DeliveryDate);

对于报告目的,在LINQ执行期间,使用消息"尚待交付"(DateTime是值类型)替换空值(基于交付日期)的方法是什么.

Answer 1

var result = DeliveryList.Select(x => new
{
    ProductCode = x.ProductCode,
    OrderedDate = x.OrderedDate,
    DeliveryDate = x.DeliveryDate.HasValue 
        ? x.DeliveryDate.Value.ToString() : "Yet to be delivered"
}).OrderBy(p => p.DeliveryDate).ToArray();