如何编写使用MVC强类型的模型DISTINCT或GROUPBY LINQ声明 [英] How to write a DISTINCT or GROUPBY LINQ statement using a strongly typed model in MVC

问题描述

我有一个名为作为调查重点如下型号;

I have a Model called Survey as highlighted below;

我想要写在我的控制器中的LINQ语句，将查询率调查表和主题返回不同的记录。每个不同的记录将有平均评分。例如;

I want to write a LINQ statement in my controller that will query the Survey Table and return distinct records by 'Topic'. Each distinct record will have an average rating. For example;

我是新来的LINQ和有创造什么，是不是基本的，当一个困难时期。

I'm new to LINQ and have a hard time when creating anything that is not basic.

我的企图;

var results = from s in db.Surveys
                      where s.Topic.Distinct()
                      select new Survey
                      {
                          SurveyId = s.SurveyId,
                          Category = s.Category.Name,
                          Topic = s.Topic,
                          Store1Rating= db.Surveys.Average(s => s.Score1).Value,
                          Store2Rating= db.Surveys.Average(s => s.Score2).Value
                      };

感谢您的帮助提前！

Thanks for your help in advance!

推荐答案

试试这个

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

namespace ConsoleApplication2
{
    class Program
    {
    static void Main(string[] args)
    {
        var survey1 = new Survey() { Topic = "topic1", Store1Rate = 5, Store2Rate = 4 };
        var survey2 = new Survey { Topic = "topic2", Store1Rate = 6, Store2Rate = 2 };
        var survey3 = new Survey { Topic = "topic2", Store1Rate = 7, Store2Rate = 2 };
        var survey4 = new Survey { Topic = "topic3", Store1Rate = 6, Store2Rate = 4 };
        var survey5 = new Survey { Topic = "topic3", Store1Rate = 1, Store2Rate = 2 };
        var survey6 = new Survey { Topic = "topic3", Store1Rate = 2, Store2Rate = 9 };

        List<Survey> surveys = new List<Survey>() { survey1, survey2, survey3, survey4, survey5, survey6 };

        var result = surveys.GroupBy(s => s.Topic).Select(s => new { Topic = s.Key, Rate1 = s.Average(a => a.Store1Rate), Rate2 = s.Average(a => a.Store2Rate) });
    }
}

class Survey
{
    public string Topic;
    public int Store1Rate;
    public int Store2Rate;
}

}

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