C# Dictionary学习

  using System;      using System.Collections;      using System.Configuration;      using System.Data;      using System.Linq;      using System.Web;      using System.Web.Security;      using System.Web.UI;      using System.Web.UI.HtmlControls;      using System.Web.UI.WebControls;      using System.Web.UI.WebControls.WebParts;      using System.Collections.Generic;      public partial class test : System.Web.UI.Page      {          protected void Page_Load(object sender, EventArgs e)          {              Dictionary<string, int> dict = new Dictionary<string, int>();              DataTable dt = GetDataTable();              if (dt != null && dt.Rows.Count > 0)              {                  foreach (DataRow dr in dt.Rows)                  {                      if (!dict.ContainsKey(dr[0].ToString()))                          dict.Add(dr[0].ToString(), Int32.Parse(dr[1].ToString()));                      //而使用索引器来赋值时，如果键已经存在，就会修改已有的键的键值                      //    dict[dr[0].ToString()] = Int32.Parse(dr[1].ToString());                                }              }              //泛型结构体              foreach (KeyValuePair<string, int> kvp in dict)                  Response.Write("key=" + kvp.Key + ",value=" + kvp.Value + "<br />");                         //输出结果：              //            key=新闻,value=3              //            key=产品,value=8              //===================================================//              Dictionary<int, Person> pdict = new Dictionary<int, Person>();              for (int i = 1; i < 3; i++)              {                  Person p = new Person();                  p.Id = i;                  p.Name = "名称 " + i;                  pdict.Add(i, p);              }              //获取值得集合              foreach (Person p in pdict.Values)              {                  Response.Write("id=" + p.Id + ",name=" + p.Name + "<br />");              }              //输出结果：              //            id=1,name=名称 1              //            id=2,name=名称 2          }          DataTable GetDataTable()          {              DataTable dt = new DataTable();              DataRow dr;              dt.Columns.Add(new DataColumn("Type", typeof(string)));              dt.Columns.Add(new DataColumn("Amount", typeof(Int32)));              dr = dt.NewRow();              dr[0] = "新闻";              dr[1] = "3";              dt.Rows.Add(dr);                    dr = dt.NewRow();              dr[0] = "产品";              dr[1] = "8";              dt.Rows.Add(dr);              dr = dt.NewRow();              dr[0] = "产品";              dr[1] = "8";              dt.Rows.Add(dr);               return dt;          }          public class Person          {              public int Id { get; set; }              public string Name { get; set; }          }            /*     //C#3.0 Dictionary初始化赋值的新语法            Dictionary<int, string> dic = new Dictionary<int, string>{           {1,"A"}, {2,"B"}, {3,"C"}, {4,"D"},{5,"E"},           {6,"F"}, {7,"G"}, {8,"H"},{9,"I"},{10,"J"},           {11,"K"},{12,"L"},{13,"M"},{14,"N"},{15,"O"},           {16,"P"},{17,"Q"},{18,"R"},{19,"S"},{20,"T"},           {21,"U"}, {22,"V"},{23,"W"}, {24,"X"},{25,"Y"},           {26,"Z"}       };       string val = dict.FirstOrDefault(d => d.Key == 2).Value;    */                       }