Int和Linq. ID [英] Int and Linq. Id

问题描述

您好，

我正在使用以下代码行生成ID:

Hello,

I am using the following code line to generate an Id:

Int32? newId = _users.Root.Elements("User").Select(a => Int32.Parse(a.Element("Id").Value)).Aggregate((Int32?)null, (x, i) => !x.HasValue || x.Value < i ? i : x);

_users是一个XDocument.如果没有找到用户，我希望newId为1；如果有用户，我希望所有ID的最大值加1.

我正在使用发布的代码:

所以以后我用:

_users is an XDocument. I would like newId to be 1 if no user is found or the Maximum value of all Ids plus 1 if there are are users.

I am using the code I am posting:

So later I use:

id == null ? 1 : newId + 1

我的问题是:

有没有办法没有最后一行.所以我想:

Int32 id =一些linq表达式，如果找不到用户，则返回1，如果有用户，则返回Max +1.

谢谢，
Miguel

My question is:

Is there a way to not have this last line. So I would like to:

Int32 id = Some linq expression that returns 1 if no user is found or Max + 1 if there are users.

Thanks,
Miguel

推荐答案

当ID为null(找不到用户)时，我使用GetValueOrDefault(1)获得1.我还修改了Agregate的功能以获取ID +1(所有ID的最大值+ 1).

I used GetValueOrDefault(1) to get 1 when Id is null (when no user is found). I also modified the function of the Agregate to get Id + 1 (Max value of all ids + 1).

 

 

            XDocument _users = new XDocument(
                new XElement("Root",
                 new XElement("User",
                     new XElement("Id", "1"),
                     new XElement("Id", "2"),
                     new XElement("Id", "3"),
                     new XElement("Id", "4"),
                     new XElement("Id", "5"),
                     new XElement("Id", "6"),
                     new XElement("Id", "7"),
                     new XElement("Id", "8"))));

            var id = _users.Root.Elements("User").
                Elements("Id").Select(e => int.Parse(e.Value)).Aggregate((int?)null, (x, i) => !x.HasValue || x.Value < i ? ++i : ++x).
                GetValueOrDefault(1);

问候.

 

Regards.

 

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