使用LINQ将多行连接成单行(CSV属性)

我正在寻找LINQ等效于Sybase的LIST()或MySQL的group_concat()

它会转换:

User  Hobby
--------------
Bob   Football 
Bob   Golf 
Bob   Tennis 
Sue   Sleeping 
Sue   Drinking

至:

User  Hobby
--------------
Bob   Football, Golf, Tennis 
Sue   Sleeping, Drinking

Jon Skeet.. 17

这就是GroupBy运营商.你在使用LINQ to Objects吗？

这是一个例子:

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

public class Test
{
    static void Main()
    {
        var users = new[]
        {
            new { User="Bob", Hobby="Football" },
            new { User="Bob", Hobby="Golf" },
            new { User="Bob", Hobby="Tennis" },
            new { User="Sue", Hobby="Sleeping" },
            new { User="Sue", Hobby="Drinking" },
        };

        var groupedUsers = users.GroupBy(user => user.User);

        foreach (var group in groupedUsers)
        {
            Console.WriteLine("{0}: ", group.Key);
            foreach (var entry in group)
            {
                Console.WriteLine("  {0}", entry.Hobby);
            }
        }
    }
}

这是分组 - 你可以自己管理其余的吗？

1> Jon Skeet..：

---

这就是GroupBy运营商.你在使用LINQ to Objects吗？

这是一个例子:

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

public class Test
{
    static void Main()
    {
        var users = new[]
        {
            new { User="Bob", Hobby="Football" },
            new { User="Bob", Hobby="Golf" },
            new { User="Bob", Hobby="Tennis" },
            new { User="Sue", Hobby="Sleeping" },
            new { User="Sue", Hobby="Drinking" },
        };

        var groupedUsers = users.GroupBy(user => user.User);

        foreach (var group in groupedUsers)
        {
            Console.WriteLine("{0}: ", group.Key);
            foreach (var entry in group)
            {
                Console.WriteLine("  {0}", entry.Hobby);
            }
        }
    }
}

这是分组 - 你可以自己管理其余的吗？

---

我是唯一一个注意到这个男人正在运动而女人的爱好是睡觉和喝酒的人吗？你是可怕的Jon Skeet!

---

只要元素的数量不是很大,也可以用`String.Join(",",group.ToArray())`替换内部循环.

2> bruno conde..：

---

看看这个解决方案是否有助于您

List users = new List() 
{ 
    new User {Name = "Bob", Hobby = "Football" },
    new User {Name = "Bob", Hobby = "Golf"},
    new User {Name = "Bob", Hobby = "Tennis"},
    new User {Name = "Sue", Hobby = "Sleeping"},
    new User {Name = "Sue", Hobby = "Drinking"}
};

var groupedUsers = from u in users
         group u by u.Name into g
         select new
         {
             Name = g.First().Name,
             Hobby = g.Select(u => u.Hobby)
         };


foreach (var user in groupedUsers)
{
    Console.WriteLine("Name: {0}", user.Name);
    foreach (var hobby in user.Hobby)
    {
        Console.WriteLine("Hobby: {0}", hobby);
    }
}

3> Ruben Bartel..：

---

使用以下方法重新_concat考虑您的问题：

static class EnumerableExtensions 
{  
    public static String AsJoined( this IEnumerable enumerable )
    {
        return AsJoined( enumerable, "," );
    }

    public static String AsJoined( this IEnumerable enumerable, String separator )
    {
        return String.Join( separator, enumerable.ToArray() );
    }
}

在bruno conde中输出的foreach和Jon Skeet的答案可以变成：

Console.WriteLine( "User:\tHobbies");
foreach ( var group in groupedUsers )
    Console.WriteLine( "{0}:\t{1}", group.Key, group.Select( g => g.Hobby ).AsJoined( ", " ) );

...，您将获得所需的精确结果输出格式（是的，我知道其他人已经解决了您的问题，但是很难抗拒！）