Question

这是我的班级：

public class Students
{
    public String StudentName
    public int CountActivities
    public List<Activities> lstActivities = new List<Activities>();
}    
public class Activities
{
    public String ActivityName
    public int ActivityScore
}

我想创建一个查询，显示学生名称为行，并将ActivityName显示为数据网格中的列。如果某项活动是由学生完成的，请在相应的行中显示该分数。细胞。我们知道活动列表的数量从1到X不等，但从不超过X.我希望CountActivities成为学生姓名旁边的第二列。第3列以后由学生参加的各种ActivityName标记。

如何创建查询以在数据网格中显示我想要的内容？我知道我必须创建一个导致List的查询。然后我可以将datagrid的源设置为List（我认为）。我的麻烦是理解如何制定查询以我刚才描述的格式呈现信息。

抱歉，我之前没有添加此部分：

List<Students> lstHighSchool = new List<Students>();
var Query = lstHighSchool ( *no clue*).ToList():
//from here I can hopefully assign List to datagrid's source.

Answer 1

在Linq中这将是困难的（并且是静态的） - 我会创建一个循环遍历活动的DataTable，如果它们不存在则创建列。

伪码：

DataTable dt
add column Name
add column CountActivities
foreach(student)
{
    add row
    row[Name] = student.Name
    row[CountActivities] = student.CountActivities
    foreach(activity)
    {
        if(! (dt contains column (activity.ActivityName)))
            add column (activity.ActivityName)
        row[activity.ActivityName] = ActivityScore
    }
}

Answer 2

我认为您的问题 具有挑战性，所以我一直在努力实现目标。不确定它是否是您想要的，它需要清理一下以使其更通用。

我的想法是构建一个linq扩展来提供您请求的结构。我正在将数据移动到元组中，其中Item1是包含StudentName的字符串，而Item2是具有足够所有不同活动名称行的ActivityScores列表。分数正确添加到与我从学生列表中创建的已排序的不同列表匹配的col中，以便为每个活动分数获得正确的col。

然后我将结果打印到调试窗口。结果对我的样本是正确的，但可能存在一些错误。无论如何，这是一个开始：）

Another path could be just to build a List<string[]> in place of the
Tuple<string, List<int>>, and everything is converted to string for display.

欢迎任何建议。

这是：

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


    namespace SO
    {
        class Program
        {
            static void Main(string[] args)
            {
                // Create Students List
                var students = new List<Student>()
                {
                    new Student
                    {
                        FirstName = "Paul",
                        LastName = "Smith",
                        ActivityList = new List<Activity>() { 
                            new Activity
                            {
                                ActivityName = "Math", ActivityScore = 90                        
                            },
                           new Activity
                            {
                                ActivityName = "Biology", ActivityScore = 92                        
                            },
                           new Activity
                            {
                                ActivityName = "C#", ActivityScore = 93                        
                            }
                        }
                    },
                    new Student
                    {
                        FirstName = "Mary",
                        LastName = "Jones",
                        ActivityList = new List<Activity>() { 
                            new Activity
                            {
                                ActivityName = "Linq", ActivityScore = 95                       
                            },
                           new Activity
                            {
                                ActivityName = "Phyics", ActivityScore = 99                        
                            },
                           new Activity
                            {
                                ActivityName = "C#", ActivityScore = 99                        
                            }
                        }
                    },
                    new Student
                    {
                        FirstName = "Slick",
                        LastName = "Willy",
                        ActivityList = new List<Activity>() { 
                            new Activity
                            {
                                ActivityName = "Wine", ActivityScore = 90                        
                            },
                           new Activity
                            {
                                ActivityName = "Women", ActivityScore = 99                        
                            },
                           new Activity
                            {
                                ActivityName = "Politics", ActivityScore = 85                        
                            }
                        }
                    }

                };



                // Created a sorted list of activity Names
                var activities = (from s in students from a in s.ActivityList select (a.ActivityName)).Distinct().ToList();
                activities.Sort();

                // Create a Tuple of <Name,Activities>
                var grid = students.DataGrid(activities);


                // Print Header
                System.Diagnostics.Debug.Write(string.Format("{0,-12}", "Name"));
                foreach (var item in activities)
                {
                   System.Diagnostics.Debug.Write(string.Format("{0,12}",item));
                }
                System.Diagnostics.Debug.WriteLine("");

                // Print Rows
                foreach (var t in grid)
                {
                    System.Diagnostics.Debug.Write(string.Format("{0,-12}", t.Item1));
                    foreach (var s in t.Item2)
                    {
                        System.Diagnostics.Debug.Write(string.Format("{0,12}", s));
                    }
                    System.Diagnostics.Debug.WriteLine("");
                }

                // Done
            }
        }



    public class Student
    {
        public String FirstName { get; set; }
        public String LastName { get; set; }
        public List<Activity> ActivityList { get; set; }
    }    

    public class Activity
    {
        public String ActivityName { get; set; }
        public int ActivityScore { get; set; }
    }


    public static class LinqExt2
    {
        public static IEnumerable<Tuple<string, System.Collections.Generic.List<int>>> DataGrid<T>(this IEnumerable<T> source, IEnumerable<string> columnList)
        {


            using (var iterator = source.GetEnumerator())
            {
                // A List of Tuples in the format <string, List<int>>
                var results = new List<Tuple<string, List<int>>>();

                // each Student
                while (iterator.MoveNext())
                {
                    var a = iterator.Current as Student;
                    if (a == null)
                        continue;

                    // initalize all cols to 0;
                    var columnValues = columnList.Select(v => 0).ToList();

                    // each Activity
                    foreach (var item in a.ActivityList)
                    {
                        var name = item.ActivityName;
                        var i = 0;
                        foreach (var activity in columnList)
                        {
                            if (name.Equals(activity))
                            {
                                columnValues[i] = item.ActivityScore;
                                break;
                            }
                            i++;
                        }
                    }
                    results.Add(Tuple.Create(a.FirstName, columnValues));
                }

                return results;
            }
        }
    }




    }

<强>结果
姓名生物学C＃Linq数学Phyics政治葡萄酒女性
保罗92 93 0 90 0 0 0 0
玛丽0 99 95 0 99 0 0 0
光滑0 0 0 0 0 85 90 99

Answer 3

您要做的事情称为“数据透视表”。

在LINQ中不可行。见（How to build pivot table through linq using c#）

请在此处查看其他选项：Pivot logic LINQ on DataTable

如何创建查询以按特定格式排列数据？

3 个答案: