使用 Linq 对基于属性的对象列表进行分组

本文关键字：列表 对象 属性 Linq 于属性 使用 | 更新日期: 2023-09-27 17:56:57

我有一个对象：

public class SiteInfo
        {
            public string Title { get; set; }
            public string URL { get; set; }
            public string Type { get; set; }     
        }

我用来创建列表： var 站点 = 新列表（）;

        foreach (SPWeb site in web.GetSubwebsForCurrentUser())
        {
            string sitetype = getConfigurationKey(site, "siteType");
            //If sites have a site type then add to list
            if (sitetype != "*ERROR*" && sitetype != "*KEYNOTFOUND*")
            {
                SiteInfo s = new SiteInfo();
                s.Title = site.Title;
                s.URL = site.Url;
                s.Type = sitetype;
                sites.Add(s);
            }
        }
        //sort list by type
        sites.Sort((x, y) => string.Compare(x.Type, y.Type));
        // serialize and send..    
        JavaScriptSerializer serializer = new JavaScriptSerializer();
        StringBuilder sbJsonResults = new StringBuilder();
        serializer.Serialize(sites, sbJsonResults);
etc.....

但是，我想做的是在序列化站点之前按类型对站点进行分组。是否可以使用 LINQ 或其他方法执行此操作。

使用 Linq 对基于属性的对象列表进行分组

听起来你想要这样的东西：

// No need to sort sites first
var grouped = sites.OrderBy(x => x.Type)
                   .GroupBy(x => x.Type);

然后只需序列化grouped.但是，我不知道 JSON 中的IGrouping会是什么样子......并且每种情况下都会存在该类型。您可能需要类似以下内容：

var grouped = sites.OrderBy(x => x.Type)
                   .GroupBy(x => x.Type)
                   .Select(g => new { Type = g.Key,
                                      Sites = g.Select(site => new {
                                                           site.Title,
                                                           site.URL
                                                       } });

我认为这会给你一个更好的JSON结构。

var sites = new List<SiteInfo>()
{
    new SiteInfo(){Title="1",Type="a",URL="http://aaaa"},
    new SiteInfo(){Title="2",Type="b",URL="http://bbbb"},
    new SiteInfo(){Title="3",Type="a",URL="http://aaaa"},
    new SiteInfo(){Title="4",Type="b",URL="http://bbb"},
};
var json = new JavaScriptSerializer().Serialize(sites.GroupBy(s => s.Type));

将产生

[
    [{"Title":"1","URL":"http://aaaa","Type":"a"},{"Title":"3","URL":"http://aaaa","Type":"a"}],
    [{"Title":"2","URL":"http://bbbb","Type":"b"},{"Title":"4","URL":"http://bbb","Type":"b"}]
]

或

var json = new JavaScriptSerializer().Serialize(sites.GroupBy(s => s.Type)
                                                      .ToDictionary(x=>x.Key,x=>x));

将产生

{
    "a":[{"Title":"1","URL":"http://aaaa","Type":"a"},{"Title":"3","URL":"http://aaaa","Type":"a"}],
    "b":[{"Title":"2","URL":"http://bbbb","Type":"b"},{"Title":"4","URL":"http://bbb","Type":"b"}]
}

下面是一个简单的控制台应用程序，可以执行您想要的操作：

static void Main(string[] args)
{
    List<SiteInfo> sites = new List<SiteInfo>()
    {
        new SiteInfo() { Title = "Site A", Type = "Whatever 2" },
        new SiteInfo() { Title = "Site B", Type = "Whatever 1" },
        new SiteInfo() { Title = "Site C", Type = "Whatever 1" },
        new SiteInfo() { Title = "Site D", Type = "Whatever 3" },
        new SiteInfo() { Title = "Site E", Type = "Whatever 3" }
    };
    var sitesGroupedByType =
        sites.GroupBy(s => s.Type).Select(g => new { Type = g.Key,
                                    Sites = g.Select(site => new
                                    {
                                          site.Title,
                                          site.URL
                                    })});
    foreach (var siteTypeGroup in sitesGroupedByType.OrderBy(g => g.Type))
    {
        foreach(var site in siteTypeGroup.Sites)
        {
            Console.WriteLine(string.Format("Type => {0}, Title => {1}",
                              siteTypeGroup.Type, site.Title));
        }
    }
    Console.ReadKey();
}

输出：

Type => Whatever 1, Title => Site B
Type => Whatever 1, Title => Site C
Type => Whatever 2, Title => Site A
Type => Whatever 3, Title => Site D
Type => Whatever 3, Title => Site E
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