Question

下面是我的格式，其中存储了我的对象数据。我是linq的新手。

Server1, Database, MySQL, 5.5
Server2, Database, MySQL, 5.1
Server3, OS, Ubuntu, 10.04
Server1, OS, Ubuntu, 10.04
Server2, OS, Ubuntu, 12.04
Server3, Language, Python, 2.6.3

以下是我的班级结构。

public class dettails
    {
        public string server { get; set; }
        public string details1 { get; set; }
        public string details2 { get; set; }
        public string version    { get; set; }

        public dettails(string Server, string Details1, string Details2, string Version)
        {
            server = Server;
            details1 = Details1;
            details2 = Details2;
            version = Version;
        }
    }

下面是在我的对象列表中添加数据的代码。

    List<dettails> objEmps = new List<dettails>();
while ((line = sr.ReadLine()) != null)
                {
    objEmps.Add(new dettails(fields[0].ToString().Trim(), fields[1].ToString().Trim(), fields[2].ToString().Trim(), fields[3].ToString().Trim()));
}

我想使用linq输出如下所示。

在至少2个不同的服务器上安装了过时版本（即非最新版本的版本）的软件包名称列表。

因此，在这种情况下，程序的输出应为：

Ubuntu的因为Ubuntu 10.04是一个过时的版本（最新版本是12.04），它安装在两个服务器上（服务器3和服务器1）。

我如何使用linq实现它。请建议

Answer 1

这是一些LINQ，发现Ubuntu已经过时了。如果您在输出要输出的问题时需要完整的解释，那将会有更多的工作。

var detailList = new List<dettails>()
{
    new dettails("Server1", "Database", "MySQL", "5.5"),
    new dettails("Server2", "Database", "MySQL", "5.1"),
    new dettails("Server3", "OS", "Ubuntu", "10.04"),
    new dettails("Server1", "OS", "Ubuntu", "10.04"),
    new dettails("Server2", "OS", "Ubuntu", "12.04"),
    new dettails("Server3", "Language", "Python", "2.6.3")
};

// 2. group details into software
var softwareGrouping = detailList.GroupBy(d => new {d.details1, d.details2});

// find software matching criteria
var obsoleteSoftware = softwareGrouping.Where(sg => sg
    // first split into versions
    .GroupBy(z => z.version)
    // sort version groups by the version number (oversimplified method)
    .OrderByDescending(z => z.Key)
    // ignore latest version
    .Skip(1)
    // get versions where installation count is greater than 1
    .Where(ss => ss.Count() > 1)
    // return if there are any old versions found
    .Any()
);

// 3. now create a result object for each found version
var results = obsoleteSoftware.Select(y => y.Key);

/* A more condensed version
var results = detailList.GroupBy(x => new {x.details1, x.details2})
    .Where(y => y.GroupBy(z => z.version).OrderByDescending(z => z.Key).Skip(1).Where(ss => ss.Count() > 1).Any())
  .Select(y => y.Key);
*/

foreach(var res in results)
{
    Console.WriteLine("{0}, {1}", res.details1, res.details2);
}

使用linq

1 个答案: