初识.net界面程序（9）--LINQ To XML

编写一个记录学生C#课成绩的XML文档，结构如下

<CScore>
  <StuID>
    <name>张三</name>
    <score>86</score>
  </StuID>
  <StuID>
    <name>李四</name>
    <score>87</score>
  </StuID>
  <StuID>
    <name>王五</name>
    <score>87</score>
  </StuID>
  <StuID>
    <name>刘七</name>
    <score>88</score>
  </StuID>
  <StuID>
    <name>张八</name>
    <score>87</score>
  </StuID>
</CScore>

给出一个分数，查找出所有成绩为次分数的学生姓名

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Xml.Linq;

namespace 补充习题
{
    public partial class Form1 : Form
    {


        public Form1()
        {
            InitializeComponent();
            textBox1.Anchor =
                AnchorStyles.Left | AnchorStyles.Right
                | AnchorStyles.Top | AnchorStyles.Bottom;
            textBox1.ScrollBars = ScrollBars.Both;
            foreach (var v in this.Controls)
            {
                Button btn = v as Button;
                if (btn != null)
                {
                    btn.Anchor = AnchorStyles.Bottom | AnchorStyles.Left;
                    btn.Click += btn_Click;
                }
            }
        }

        void btn_Click(object sender, EventArgs e)
        {
            string vlaue = textBox2.Text;
            string s = (sender as Button).Text;
            switch (s)
            {
                case "创建":
                    {

                        XElement xTree = new XElement("CScore",

                            new XElement("StuID",
                              new XElement("name", "张三"),
                              new XElement("score", 86)
                            ),
                            new XElement("StuID",
                              new XElement("name", "李四"),
                              new XElement("score", 87)
                            ),
                            new XElement("StuID",
                              new XElement("name", "王五"),
                              new XElement("score", 87)
                            ),
                            new XElement("StuID",
                              new XElement("name", "刘七"),
                              new XElement("score", 88)
                            ),
                            new XElement("StuID",
                              new XElement("name", "张八"),
                              new XElement("score", 87)
                            )
                        );

                        textBox1.Text = xTree.ToString();
                        xTree.Save("test.xml");
                        break;
                    }
                case "查询":
                    {
                        StringBuilder sb = new StringBuilder();
                        XElement CScore = null;
                        try
                        {
                            CScore = XElement.Load("test.xml");
                        }
                        catch
                        {
                            MessageBox.Show("请先执行【创建】");
                            return;
                        }
                        var q1 = from t in CScore.Elements("StuID")
                                 select t;

                        var q2 = from t in q1
                                 where (string)t.Element("score") == vlaue
                                 select t.Element("name");
                        foreach (var v in q2)
                        {
                            sb.AppendLine(v.Value.ToString());
                        }
                        //sb.AppendLine();
                        textBox1.Text = sb.ToString();
                        break;
                    }
            }
        }
    }
}