稍微复杂的c# linq

本文关键字：linq 复杂 | 更新日期: 2023-09-27 18:09:17

在检索数据服务器端计数之前，我问了一个问题，并在网站上提供了解决方案。我的建议是使用linq，它工作得很好，但是因为我对它比较陌生，我需要一点深入的帮助。

使用John的解决方案:

class Guy
{
    public int age; public string name;
    public Guy( int age, string name ) {
        this.age = age;
        this.name = name;
    }
}
class Program
{
    static void Main( string[] args ) {
        var GuyArray = new Guy[] { 
        new Guy(22,"John"),new Guy(25,"John"),new Guy(27,"John"),new Guy(29,"John"),new Guy(12,"Jack"),new Guy(32,"Jack"),new Guy(52,"Jack"),new Guy(100,"Abe")};
    var peeps = from f in GuyArray group f by f.name into g select new { name = g.Key, count = g.Count() };
        foreach ( var record in peeps ) {
            Console.WriteLine( record.name + " : " + record.count );
        }
    }
}

我可以根据John的建议使用上面的方法得到John, Jake和Abe出现的次数。但是，如果问题稍微复杂一些呢?例如

var GuyArray = new Guy[] { 
new Guy(22,"John", "happy"),new Guy(25,"John", "sad"),new Guy(27,"John", "ok"),
new Guy(29,"John", "happy"),new Guy(12,"Jack", "happy"),new Guy(32,"Jack", "happy"),
new Guy(52,"Jack", "happy"),new Guy(100,"Abe", "ok")};

上面的代码可以很好地检索不同名字的出现次数，但是如果我需要这些名字的出现次数以及每个人快乐、悲伤或ok的出现次数该怎么办?ie的输出是:名称，名称计数，快乐的名称计数，悲伤的名称计数，ok的名称计数。如果linq不是最好的解决方案，我准备听取所有替代方案。非常感谢您的帮助。

稍微复杂的c# linq

坦白地说，我们并不清楚你想要的是快乐的总人数，还是快乐的总人数(也包括悲伤的人数)。我给你一个两全其美的办法。

var nameGroups = from guy in GuyArray 
                 group guy by guy.name into g
                 select new { 
                     name = g.Key,
                     count = g.Count(),
                     happy = g.Count(x => x.status == "happy"),
                     sad = g.Count(x => x.status == "sad"),
                     ok = g.Count(x => x.status == "ok")
                 };

: 

foreach(nameGroup in nameGroups) {
    Console.WriteLine("Name = {0}, Count = {1}, Happy count = {2}, Sad count = {3}, Okay count = {4}", nameGroup.name, nameGroup.count, nameGroup.happy, nameGroup.sad, nameGroup.ok);
}

如果你想知道快乐，悲伤，ok的总数，你可以说:

Console.WriteLine(nameGroups.Sum(nameGroup => nameGroup.happy));

等。

另外，你应该创建一个enum

public enum Mood {
    Happy,
    Sad,
    Okay
}

然后

class Guy {
    public int Age { get; set; }
    public string Name { get; set; }
    public Mood Mood { get; set; }
}

，这样你就可以写:

var people = from guy in guyArray 
             group guy by guy.Name into g
             select new { 
                 Name = g.Key,
                 Count = g.Count(),
                 HappyCount = g.Count(x => x.Mood == Mood.Happy),
                 SadCount = g.Count(x => x.Mood == Mood.Sad),
                 OkayCount = g.Count(x => x.Mood == Mood.Okay)
             };

To do so: 
   class Guy
    {
        public int age; public string name; string mood;
        public Guy( int age, string name,string mood ) {
            this.age = age;
            this.name = name;
            this.mood = mood;
        }
    }
    class Program
    {
        static void Main( string[] args ) {
           var GuyArray = new Guy[] { 
new Guy(22,"John", "happy"),new Guy(25,"John", "sad"),new Guy(27,"John", "ok"),
new Guy(29,"John", "happy"),new Guy(12,"Jack", "happy"),new Guy(32,"Jack", "happy"),
new Guy(52,"Jack", "happy"),new Guy(100,"Abe", "ok")};

        var peepsSad = from f in GuyArray where f.mood=="sad" group f by f.name into g select new { name = g.Key, count = g.Count() };
 var peepsHappy = from f in GuyArray where f.mood=="happy" group f by f.name into g select new { name = g.Key, count = g.Count() };
 var peepsOk = from f in GuyArray where f.mood=="ok" group f by f.name into g select new { name = g.Key, count = g.Count() };

            foreach ( var record in peepsSad ) {
                Console.WriteLine( record.name + " : " + record.count );
            }
  foreach ( var record in peepsHappy ) {
                Console.WriteLine( record.name + " : " + record.count );
            }
  foreach ( var record in peepsOk ) {
                Console.WriteLine( record.name + " : " + record.count );
            }
        }
    }
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