系统提示说错误    1    当前上下文中不存在名称“persons”   
前面明明定义了一个集合‘persins'的，，想不明白是哪里写错了


using System.Collections.Generic;
using
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Collections;

namespace WindowsFormsApplication1
{
    public partial class SayHi : Form
    {
   
        public SayHi()
        {
            InitializeComponent();
        }
        class PersonInfo
        {
            public string Name { get; set; }
            public char Sex { get; set; }
            public int Age { get; set; }

            public PersonInfo(string name, char sex, int age)
            {
                this.Name = name;
                this.Sex = sex;
                this.Age = age;
            }
        }
        class Sample
        {
            List<PersonInfo> persons = new List<PersonInfo>   //定义persons集合

            {
                new PersonInfo("赵灵儿",'女',16),
                new PersonInfo("林月如",'男',18),
                new PersonInfo("李逍遥",'女',22),
                new PersonInfo("一如",'女',7),
            };
        }
      
        private void btnCount_Click(object sender, EventArgs e)
        {
            
            var orderBy = persons.Select     //提示说上下文没有“persons"这个名称
                (name => "你好！" + name)
                .OrderBy(name => name.Sustring(0, 1));
            string nameList = "";
            foreach (var item in orderBy)
            {
                nameList += item + "\t";
            }
            MessageBox.Show(nameList);
        }
   
        
 
   
    }

}

错是"persons"就在"sample"存:

class Sample
{
    public static List<PersonInfo> persons = new List<PersonInfo>   //定义persons集合
    {
        new PersonInfo("赵灵儿",'女',16),
        new PersonInfo("林月如",'男',18),
        new PersonInfo("李逍遥",'女',22),
        new PersonInfo("一如",'女',7),
    };
}

private void btnCount_Click(object sender, EventArgs e)
{
   
    var orderBy = Sample.persons.Select
        (name => "你好！" + name)
        .OrderBy(name => name.Sustring(0, 1));
    string nameList = "";
    foreach (var item in orderBy)
    {
        nameList += item + "\t";
    }
    MessageBox.Show(nameList);
}

此外你应该写:

...
private void btnCount_Click(object sender, EventArgs e)
{
    var orderBy = persons.OrderBy(person => person.Name.Substring(0, 1))
                         .Select(person => "你好！" + person.Name);
    ...

   private void btnCount_Click(object sender, EventArgs e)
        {
            var orderBy = persons.OrberBy(person => person.Name.Substring(0, 1))//
                                .Select(person => "你好！" + Name);
            string nameList = "";
            foreach (var item in orderBy)
            {
                nameList += item + "\n";
            }
            MessageBox.Show(nameList);
        }
    }
照你说的写，还是报相同的错误“persons"不存在！会不会类的顺序放错了？？

这应该OK :

private void btnCount_Click(object sender, EventArgs e)
{
    var orderBy = Sample.persons.OrderBy(person => person.Name.Substring(0, 1))
                                .Select(person => "你好！" + person.Name);

namespace WindowsFormsApplication1
{
    public partial class SayHi : Form
    {

        public SayHi()
        {
            InitializeComponent();
        }

        List<PersonInfo> persons = new List<PersonInfo>

            {
                new PersonInfo("赵灵儿",'女',16),
                new PersonInfo("林月如",'男',18),
                new PersonInfo("李逍遥",'女',22),
                new PersonInfo("一如",'女',7),
            };

        private void btnCount_Click(object sender, EventArgs e)
        {

            var orderBy = persons.Select(person => "你好！"+Name)
                                .OrderBy(person => Name.Substring(0,1));
            string nameList = "";
            foreach (var item in orderBy)
            {
                nameList += item + "\n";
            }
            MessageBox.Show(nameList);
        }
    }

    class PersonInfo
    {
        public string Name { get; set; }
        public char Sex { get; set; }
        public int Age { get; set; }

        public PersonInfo(string name, char sex, int age)
        {
            this.Name = name;
            this.Sex = sex;
            this.Age = age;
        }

    }
   应该这样写才对，集合应该写在和方法写在同一个类里面