Question

我在此表中有一个列表

var max = db.Fruits.Max();

我想知道这个表中最常见的水果是什么，这个结果对我来说是什么代码我正在使用

{{1}}

有错误吗？

Answer 1

如果您想获得列表中最重要的项目名称，请先找到最常出现的ID：

function loadLikesAndCommentsNotifications (request) {
    var currentUser = Parse.User.current();

    var query3 = new Parse.Query("Posts"); 
    query3.equalTo("driver", currentUser); 

    var query4 = new Parse.Query("Posts");
    query4.equalTo("passengers", currentUser.get("objectId")); 

    var main2 = new Parse.Query.or(query3, query4); 

    var main3  = new Parse.Query("Comments"); 
    main3.matchesKeyInQuery('postId', 'objectId', main2);

    var main4 = new Parse.Query("Comments"); 
    main4.equalTo("commentBy", currentUser); 

    var activityQuery = new Parse.Query.or(main3, main4); 
    activityQuery.include("commentBy");
    activityQuery.limit(15); 

    return activityQuery.find();
}

Parse.Cloud.define("loadLikesAndCommentsNotifications", function(request, response){
    loadLikesAndCommentsNotifications(request).then(response.success, response.error);
});

...
// Similar code for loadRequestNotifications
...

Parse.Cloud.define("loadRequestAndLikesAndCommentsNotifications", function(request, response){
    loadLikesAndCommentsNotifications(request).then(function (results) {
        var finalResults = { likesAndComments: results};
        loadRequestNotifications(request).then(function (results) {
            finalResults.request = results;
            response.success(finalResults);
        }, response.error);
    }, response.error);
});

这将返回一个最常见的var fruitAnon = fruits .GroupBy(item => item.ID) .Select(item => new { Key = item.Key, Count = item.Count() }) .OrderByDescending(item => item.Count) .FirstOrDefault();匿名对象，id表示它在列表中的存在次数。然后，您可以找到该对象的名称：

count

如果您有这样的列表：

var fruit = fruits.FirstOrDefault(x => x.ID == fruitAnon.Key);

然后：

List<Fruits> fruits = new List<Fruits>() {
    new Fruits { ID = 1, Name = "Apple" },
    new Fruits { ID = 1, Name = "Apple" },
    new Fruits { ID = 2, Name = "Orange" },
    new Fruits { ID = 2, Name = "Orange" },
    new Fruits { ID = 2, Name = "Orange" },
    new Fruits { ID = 2, Name = "Orange" }
};

会打印Console.WriteLine(fruit.Name);。

Answer 2

尝试

public class Fruits
    {

        public int ID { get; set; }

        public string Name{ get; set; }
}


var Val = fruitList.GroupBy(x => x.ID,
                         (key, y) => y.MaxBy(x => x.ID).value)

Answer 3

正如Drew在评论中所说，你想要GroupBy你关心的值（我做了Name，因为ID在大多数数据结构中往往是唯一的），然后是基于计数的OrderByDescending。

using System;
using System.Collections.Generic;
using System.Linq;

public class Program
{
    public static void Main()
    {
        var fruits = new List<Fruit> { new Fruit { ID = 1, Name = "Apple" }, new Fruit { ID = 2, Name = "Apple" }, new Fruit { ID = 3, Name = "Pear" } };   
        var most = fruits.GroupBy(f => f.Name).OrderByDescending(group => group.Count());
        Console.WriteLine(most.First().Key);
    }
}

public class Fruit
{
    public int ID { get; set; }
    public string Name{ get; set; }
}

列表中最常出现的项目

3 个答案: