下面是一个示例，展示了如何使用LINQ按列分组并显示所有列的值：

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

public class Program
{
    public static void Main(string[] args)
    {
        // 创建一个包含多个列的示例数据集合
        List people = new List()
        {
            new Person { Name = "John", Age = 30, City = "New York" },
            new Person { Name = "Jane", Age = 25, City = "London" },
            new Person { Name = "Bob", Age = 35, City = "Paris" },
            new Person { Name = "Alice", Age = 28, City = "Tokyo" },
            new Person { Name = "Mike", Age = 32, City = "New York" }
        };

        // 使用LINQ按"City"列分组并显示所有列的值
        var groupedData = from p in people
                          group p by p.City into g
                          select new { City = g.Key, People = g.ToList() };

        // 显示每个分组的数据
        foreach (var group in groupedData)
        {
            Console.WriteLine($"City: {group.City}");
            foreach (var person in group.People)
            {
                Console.WriteLine($"Name: {person.Name}, Age: {person.Age}");
            }
            Console.WriteLine();
        }
    }

    public class Person
    {
        public string Name { get; set; }
        public int Age { get; set; }
        public string City { get; set; }
    }
}

以上示例创建了一个包含多个人员信息的数据集合。然后，使用LINQ的group by子句按照"City"列进行分组，并将结果存储在groupedData变量中。最后，使用foreach循环遍历每个分组，并显示每个分组的城市和相应的人员信息。

输出结果为：

City: New York
Name: John, Age: 30
Name: Mike, Age: 32

City: London
Name: Jane, Age: 25

City: Paris
Name: Bob, Age: 35

City: Tokyo
Name: Alice, Age: 28

该示例演示了如何使用LINQ按列分组并显示所有列的值。你可以根据自己的需求进行修改和扩展。