Question

我有一个包含两个属性的列表，Lastname和Firstname。它们可以为空，应该是。

这是我的代码行：

return memberlist.OrderBy(x => x.LastName).ThenBy(x => x.Firstname);

我的问题是，如果Lastname为null，它将运行ThenBy（）而Else我需要创建一个nullcheck吗？我想确保它按姓氏排序，如果是null，则按名字命令。

假设我有一个如下所示的列表：

var data = new List<Member>
{
    new Member { FirstName = "null", LastName = "A" },
    new Member { FirstName = "B", LastName = null },
    new Member { FirstName = "A", LastName = null },
    new Member { FirstName = null , LastName = "B" },
    new Member { FirstName = "A" , LastName = "B" },
    new Member { FirstName = "B" , LastName = "A" },
};

我希望输出如下：

A
A
A
B
B
B

var result = data.OrderBy(x => x.LastName).ThenBy(x => x.FirstName);

Answer 1

是的，它会运行ThenBy()。

基本上，具有null LastName属性的所有项目将由FirstName按然后排序。

OrderBy()会将null值放在非空值之前。

在以下示例中，result按照声明的顺序返回项目：

var data = new List<Member>
{
    new Member { FirstName = "A", LastName = null },
    new Member { FirstName = "B", LastName = null },
    new Member { FirstName = "A", LastName = "NotNull" },
    new Member { FirstName = "B", LastName = "NotNull" }
};

var result = data.OrderBy(x => x.LastName).ThenBy(x => x.FirstName);

修改

根据以下评论和问题更新，您可以使用以下内容在OrderBy()和FirstName的逻辑组合上执行LastName：

var result = data.OrderBy(x => string.IsNullOrWhiteSpace(x.LastName) ? x.FirstName : x.LastName) .ThenBy(x => x.FirstName)

当我在我的orderby中使用两个可空属性时，是否需要nullcheck？

1 个答案: