C# WinForm ComboBox Items 选定值

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

namespace WindowsFormsApplication3
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        class User
        {
            public int id { get; set; }
            public string name { get; set; }
        }


        private void Form1_Load(object sender, EventArgs e)
        {
            List<User> collection = new List<User>
            {
                new User { id = 1, name = "Lin" },
                new User { id = 2, name = "Tom" },
                new User { id = 3, name = "Jack" },
            };

            this.comboBox1.DisplayMember = "name";
            this.comboBox1.ValueMember = "id";
            this.comboBox1.DropDownStyle = ComboBoxStyle.DropDownList;

            //Items     加载 默认选择为空
            //DataSoursce 加载 默认选择为首项
            this.comboBox1.Items.Clear();
            this.comboBox1.Items.AddRange(collection.ToArray()); 
            //this.comboBox1.DataSource = collection;            
        }

        //设置选择 id = 2 的 User
        private void button1_Click(object sender, EventArgs e)
        {
            var items = this.comboBox1.Items;
            for (int i = 0; i < items.Count; i++)
            {
                User item = items[i] as User;
                if (item.id == 2)
                {
                    this.comboBox1.SelectedItem = item;
                    break;
                }
            }
        }
    }
}