11.5.1 使用 join 子句的内连接

如果你打算把一个巨大的序列连接到一个极小的序列上，应尽可能把小序列作为右边序列

  1.      class Program
  2.      {
  3.          static void Main(string[] args)
  4.          {
  5.              var query = from defect in SampleData.AllDefects
  6.                          join subscription in SampleData.AllSubscriptions
  7.                          on defect.Project equals subscription.Project
  8.                          select new { defect.Summary, subscription.EmailAddress };
  9.  
  10.              foreach (var item in query)
  11.              {
  12.                  Console.WriteLine("{0} {1}", item.Summary, item.EmailAddress);
  13.              }
  14.  
  15.              Console.ReadKey();
  16.          }
  17.      }

我们通常需要对序列进行过滤，而在连接前进行过滤比在连接后过滤效率要高得多。
在这个阶段，假如只有左边的序列需要进行过滤，查询表达式相对简单一些。例如，如果我们只想显示已经关闭的缺陷，我们可以使用下面的查询表达式

  1.      class Program
  2.      {
  3.          static void Main(string[] args)
  4.          {
  5.              var query = from defect in SampleData.AllDefects
  6.                          where defect.Status == Status.Closed
  7.                          join subscription in SampleData.AllSubscriptions
  8.                          on defect.Project equals subscription.Project
  9.                          select new { defect.Summary, subscription.EmailAddress };
  10.  
  11.              var query2 = from subscription in SampleData.AllSubscriptions
  12.                           join defect in (from defect in SampleData.AllDefects
  13.                                           where defect.Status == Status.Closed
  14.                                           select defect)
  15.                           on subscription.Project equals defect.Project
  16.                           select new { defect.Summary, subscription.EmailAddress };
  17.  
  18.              foreach (var item in query)
  19.              {
  20.                  Console.WriteLine("{0} {1}", item.Summary, item.EmailAddress);
  21.              }
  22.  
  23.              Console.ReadKey();
  24.          }
  25.      }

11.5.2 使用 join...into 子句进行分组连接

  1.      class Program
  2.      {
  3.          static void Main(string[] args)
  4.          {
  5.              var query = from defect in SampleData.AllDefects
  6.                          join subscription in SampleData.AllSubscriptions
  7.                          on defect.Project equals subscription.Project
  8.                          into groupSubscriptions
  9.                          select new { Defect = defect, Subscription = groupSubscriptions };
  10.  
  11.              foreach (var entry in query)
  12.              {
  13.                  Console.WriteLine(entry.Defect.Summary);
  14.                  foreach (var subscription in entry.Subscription)
  15.                  {
  16.                      Console.WriteLine("         {0} ", subscription.EmailAddress);
  17.                  }
  18.              }
  19.  
  20.              Console.ReadKey();
  21.          }
  22.      }
  1.      class Program
  2.      {
  3.          static void Main(string[] args)
  4.          {
  5.              var dates = new DateTimeRange(SampleData.Start, SampleData.End);
  6.  
  7.              var query = from date in dates
  8.                          join defect in SampleData.AllDefects
  9.                          on date equals defect.Created.Date
  10.                          into joined
  11.                          select new { Date = date, Count = joined.Count() };
  12.  
  13.              var query2 = dates.GroupJoin(SampleData.AllDefects,
  14.                                          date => date,
  15.                                          defect => defect.Created.Date,
  16.                                          (date, joined) => new { Date = date, Count = joined.Count() });
  17.  
  18.              foreach (var item in query)
  19.              {
  20.                  Console.WriteLine("{0:d} {1}", item.Date, item.Count);
  21.              }
  22.  
  23.              Console.ReadKey();
  24.          }
  25.      }

11.5.3 使用多个 from 子句进行交叉连接和合并序列

  1.      class Program
  2.      {
  3.          static void Main(string[] args)
  4.          {
  5.              var query = from left in Enumerable.Range(, )
  6.                          from right in Enumerable.Range(, left)
  7.                          select new { Left = left, Right = right };
  8.  
  9.              var query2 = Enumerable.Range(, )
  10.                  .SelectMany(left => Enumerable.Range(, left),
  11.                              (left, right) => new { Left = left, Right = right });
  12.  
  13.              foreach (var item in query)
  14.              {
  15.                  Console.WriteLine("Left= {0} Right= {1} ", item.Left, item.Right);
  16.              }
  17.  
  18.              Console.ReadKey();
  19.          }
  20.      }

SampleData代码，如下

  1.      public class SampleData
  2.      {
  3.          static List<Defect> defects;
  4.          static List<User> users;
  5.          static List<Project> projects;
  6.          static List<NotificationSubscription> subscriptions;
  7.  
  8.          public static readonly DateTime Start = May();
  9.          public static readonly DateTime End = May();
  10.  
  11.          public static IEnumerable<Defect> AllDefects
  12.          {
  13.              get { return defects; }
  14.          }
  15.  
  16.          public static IEnumerable<User> AllUsers
  17.          {
  18.              get { return users; }
  19.          }
  20.  
  21.          public static IEnumerable<Project> AllProjects
  22.          {
  23.              get { return projects; }
  24.          }
  25.  
  26.          public static IEnumerable<NotificationSubscription> AllSubscriptions
  27.          {
  28.              get { return subscriptions; }
  29.          }
  30.  
  31.          public static class Projects
  32.          {
  33.              public static readonly Project SkeetyMediaPlayer = new Project { Name = "Skeety Media Player" };
  34.              public static readonly Project SkeetyTalk = new Project { Name = "Skeety Talk" };
  35.              public static readonly Project SkeetyOffice = new Project { Name = "Skeety Office" };
  36.          }
  37.  
  38.          public static class Users
  39.          {
  40.              public static readonly User TesterTim = new User("Tim Trotter", UserType.Tester);
  41.              public static readonly User TesterTara = new User("Tara Tutu", UserType.Tester);
  42.              public static readonly User DeveloperDeborah = new User("Deborah Denton", UserType.Developer);
  43.              public static readonly User DeveloperDarren = new User("Darren Dahlia", UserType.Developer);
  44.              public static readonly User ManagerMary = new User("Mary Malcop", UserType.Manager);
  45.              public static readonly User CustomerColin = new User("Colin Carton", UserType.Customer);
  46.          }
  47.  
  48.          static SampleData()
  49.          {
  50.              projects = new List<Project>
  51.              {
  52.                  Projects.SkeetyMediaPlayer,
  53.                  Projects.SkeetyTalk,
  54.                  Projects.SkeetyOffice
  55.              };
  56.  
  57.              users = new List<User>
  58.              {
  59.                  Users.TesterTim,
  60.                  Users.TesterTara,
  61.                  Users.DeveloperDeborah,
  62.                  Users.DeveloperDarren,
  63.                  Users.ManagerMary,
  64.                  Users.CustomerColin
  65.              };
  66.  
  67.              subscriptions = new List<NotificationSubscription>
  68.              {
  69.                  new NotificationSubscription { Project=Projects.SkeetyMediaPlayer, EmailAddress="media-bugs@skeetysoft.com" },
  70.                  new NotificationSubscription { Project=Projects.SkeetyTalk, EmailAddress="talk-bugs@skeetysoft.com" },
  71.                  new NotificationSubscription { Project=Projects.SkeetyOffice, EmailAddress="office-bugs@skeetysoft.com" },
  72.                  new NotificationSubscription { Project=Projects.SkeetyMediaPlayer, EmailAddress="theboss@skeetysoft.com"}
  73.              };
  74.  
  75.              defects = new List<Defect>
  76.              {
  77.                  new Defect
  78.                  {
  79.                      Project = Projects.SkeetyMediaPlayer,
  80.                      Created = May(),
  81.                      CreatedBy = Users.TesterTim,
  82.                      Summary = "MP3 files crash system",
  83.                      Severity = Severity.Showstopper,
  84.                      AssignedTo = Users.DeveloperDarren,
  85.                      Status = Status.Accepted,
  86.                      LastModified = May()
  87.                  },
  88.  
  89.                  new Defect
  90.                  {
  91.                      Project = Projects.SkeetyMediaPlayer,
  92.                      Created = May(),
  93.                      CreatedBy = Users.DeveloperDeborah,
  94.                      Summary = "Text is too big",
  95.                      Severity = Severity.Trivial,
  96.                      AssignedTo = null,
  97.                      Status = Status.Closed,
  98.                      LastModified = May()
  99.                  },
  100.  
  101.                  new Defect
  102.                  {
  103.                      Project = Projects.SkeetyTalk,
  104.                      Created = May(),
  105.                      CreatedBy = Users.CustomerColin,
  106.                      Summary = "Sky is wrong shade of blue",
  107.                      Severity = Severity.Minor,
  108.                      AssignedTo = Users.TesterTara,
  109.                      Status = Status.Fixed,
  110.                      LastModified = May()
  111.                  },
  112.  
  113.                  new Defect
  114.                  {
  115.                      Project = Projects.SkeetyMediaPlayer,
  116.                      Created = May(),
  117.                      CreatedBy = Users.DeveloperDarren,
  118.                      Summary = "Can't play files more than 200 bytes long",
  119.                      Severity = Severity.Major,
  120.                      AssignedTo = Users.DeveloperDarren,
  121.                      Status = Status.Reopened,
  122.                      LastModified = May()
  123.                  },
  124.  
  125.                  new Defect
  126.                  {
  127.                      Project = Projects.SkeetyMediaPlayer,
  128.                      Created = May(),
  129.                      CreatedBy = Users.TesterTim,
  130.                      Summary = "Installation is slow",
  131.                      Severity = Severity.Trivial,
  132.                      AssignedTo = Users.TesterTim,
  133.                      Status = Status.Fixed,
  134.                      LastModified = May()
  135.                  },
  136.  
  137.                  new Defect
  138.                  {
  139.                      Project = Projects.SkeetyMediaPlayer,
  140.                      Created = May(),
  141.                      CreatedBy = Users.ManagerMary,
  142.                      Summary = "DivX is choppy on Pentium 100",
  143.                      Severity = Severity.Major,
  144.                      AssignedTo = Users.DeveloperDarren,
  145.                      Status = Status.Accepted,
  146.                      LastModified = May()
  147.                  },
  148.  
  149.                  new Defect
  150.                  {
  151.                      Project = Projects.SkeetyTalk,
  152.                      Created = May(),
  153.                      CreatedBy = Users.DeveloperDeborah,
  154.                      Summary = "Client acts as virus",
  155.                      Severity = Severity.Showstopper,
  156.                      AssignedTo = null,
  157.                      Status = Status.Closed,
  158.                      LastModified = May()
  159.                  },
  160.  
  161.                  new Defect
  162.                  {
  163.                      Project = Projects.SkeetyMediaPlayer,
  164.                      Created = May(),
  165.                      CreatedBy = Users.DeveloperDarren,
  166.                      Summary = "Subtitles only work in Welsh",
  167.                      Severity = Severity.Major,
  168.                      AssignedTo = Users.TesterTim,
  169.                      Status = Status.Fixed,
  170.                      LastModified = May()
  171.                  },
  172.  
  173.                  new Defect
  174.                  {
  175.                      Project = Projects.SkeetyTalk,
  176.                      Created = May(),
  177.                      CreatedBy = Users.CustomerColin,
  178.                      Summary = "Voice recognition is confused by background noise",
  179.                      Severity = Severity.Minor,
  180.                      AssignedTo = null,
  181.                      Status = Status.Closed,
  182.                      LastModified = May()
  183.                  },
  184.  
  185.                  new Defect
  186.                  {
  187.                      Project = Projects.SkeetyTalk,
  188.                      Created = May(),
  189.                      CreatedBy = Users.TesterTim,
  190.                      Summary = "User interface should be more caramelly",
  191.                      Severity = Severity.Trivial,
  192.                      AssignedTo = Users.DeveloperDarren,
  193.                      Status = Status.Created,
  194.                      LastModified = May()
  195.                  },
  196.  
  197.                  new Defect
  198.                  {
  199.                      Project = Projects.SkeetyMediaPlayer,
  200.                      Created = May(),
  201.                      CreatedBy = Users.ManagerMary,
  202.                      Summary = "Burning a CD makes the printer catch fire",
  203.                      Severity = Severity.Showstopper,
  204.                      AssignedTo = null,
  205.                      Status = Status.Closed,
  206.                      LastModified = May()
  207.                  },
  208.  
  209.                  new Defect
  210.                  {
  211.                      Project = Projects.SkeetyTalk,
  212.                      Created = May(),
  213.                      CreatedBy = Users.TesterTara,
  214.                      Summary = "Peer to peer pairing passes parameters poorly",
  215.                      Severity = Severity.Minor,
  216.                      AssignedTo = Users.DeveloperDarren,
  217.                      Status = Status.Accepted,
  218.                      LastModified = May()
  219.                  },
  220.  
  221.                  new Defect
  222.                  {
  223.                      Project = Projects.SkeetyTalk,
  224.                      Created = May(),
  225.                      CreatedBy = Users.DeveloperDarren,
  226.                      Summary = "Delay when sending message",
  227.                      Severity = Severity.Minor,
  228.                      AssignedTo = Users.TesterTara,
  229.                      Status = Status.Fixed,
  230.                      LastModified = May()
  231.                  },
  232.  
  233.                  new Defect
  234.                  {
  235.                      Project = Projects.SkeetyMediaPlayer,
  236.                      Created = May(),
  237.                      CreatedBy = Users.ManagerMary,
  238.                      Summary = "Volume control needs to go to 11",
  239.                      Severity = Severity.Minor,
  240.                      AssignedTo = Users.DeveloperDarren,
  241.                      Status = Status.Created,
  242.                      LastModified = May()
  243.                  },
  244.  
  245.                  new Defect
  246.                  {
  247.                      Project = Projects.SkeetyMediaPlayer,
  248.                      Created = May(),
  249.                      CreatedBy = Users.CustomerColin,
  250.                      Summary = "Splash screen fades too quickly",
  251.                      Severity = Severity.Minor,
  252.                      AssignedTo = Users.TesterTara,
  253.                      Status = Status.Fixed,
  254.                      LastModified = May()
  255.                  },
  256.  
  257.                  new Defect
  258.                  {
  259.                      Project = Projects.SkeetyTalk,
  260.                      Created = May(),
  261.                      CreatedBy = Users.DeveloperDeborah,
  262.                      Summary = "Text box doesn't keep up with fast typing",
  263.                      Severity = Severity.Major,
  264.                      AssignedTo = Users.DeveloperDeborah,
  265.                      Status = Status.Accepted,
  266.                      LastModified = May()
  267.                  },
  268.  
  269.                  new Defect
  270.                  {
  271.                      Project = Projects.SkeetyTalk,
  272.                      Created = May(),
  273.                      CreatedBy = Users.DeveloperDarren,
  274.                      Summary = "Password displayed in plain text",
  275.                      Severity = Severity.Showstopper,
  276.                      AssignedTo = null,
  277.                      Status = Status.Closed,
  278.                      LastModified = May()
  279.                  },
  280.  
  281.                  new Defect
  282.                  {
  283.                      Project = Projects.SkeetyMediaPlayer,
  284.                      Created = May(),
  285.                      CreatedBy = Users.TesterTim,
  286.                      Summary = "Play button points the wrong way",
  287.                      Severity = Severity.Major,
  288.                      AssignedTo = Users.TesterTim,
  289.                      Status = Status.Fixed,
  290.                      LastModified = May()
  291.                  },
  292.  
  293.                  new Defect
  294.                  {
  295.                      Project = Projects.SkeetyMediaPlayer,
  296.                      Created = May(),
  297.                      CreatedBy = Users.CustomerColin,
  298.                      Summary = "Wizard needed for CD burning",
  299.                      Severity = Severity.Minor,
  300.                      AssignedTo = Users.CustomerColin,
  301.                      Status = Status.Fixed,
  302.                      LastModified = May()
  303.                  },
  304.  
  305.                  new Defect
  306.                  {
  307.                      Project = Projects.SkeetyMediaPlayer,
  308.                      Created = May(),
  309.                      CreatedBy = Users.ManagerMary,
  310.                      Summary = "Subtitles don't display during fast forward",
  311.                      Severity = Severity.Trivial,
  312.                      AssignedTo = Users.DeveloperDarren,
  313.                      Status = Status.Accepted,
  314.                      LastModified = May()
  315.                  },
  316.  
  317.                  new Defect
  318.                  {
  319.                      Project = Projects.SkeetyMediaPlayer,
  320.                      Created = May(),
  321.                      CreatedBy = Users.DeveloperDarren,
  322.                      Summary = "Memory leak when watching Memento",
  323.                      Severity = Severity.Trivial,
  324.                      AssignedTo = Users.DeveloperDeborah,
  325.                      Status = Status.Created,
  326.                      LastModified = May()
  327.                  },
  328.  
  329.                  new Defect
  330.                  {
  331.                      Project = Projects.SkeetyTalk,
  332.                      Created = May(),
  333.                      CreatedBy = Users.DeveloperDeborah,
  334.                      Summary = "Profile screen shows login count of -1",
  335.                      Severity = Severity.Major,
  336.                      AssignedTo = Users.DeveloperDeborah,
  337.                      Status = Status.Accepted,
  338.                      LastModified = May()
  339.                  },
  340.  
  341.                  new Defect
  342.                  {
  343.                      Project = Projects.SkeetyTalk,
  344.                      Created = May(),
  345.                      CreatedBy = Users.TesterTim,
  346.                      Summary = "Server crashes under heavy load (3 users)",
  347.                      Severity = Severity.Major,
  348.                      AssignedTo = Users.DeveloperDeborah,
  349.                      Status = Status.Accepted,
  350.                      LastModified = May()
  351.                  },
  352.  
  353.                  new Defect
  354.                  {
  355.                      Project = Projects.SkeetyMediaPlayer,
  356.                      Created = May(),
  357.                      CreatedBy = Users.TesterTara,
  358.                      Summary = "Unable to connect to any media server",
  359.                      Severity = Severity.Showstopper,
  360.                      AssignedTo = Users.DeveloperDarren,
  361.                      Status = Status.Reopened,
  362.                      LastModified = May()
  363.                  },
  364.  
  365.                  new Defect
  366.                  {
  367.                      Project = Projects.SkeetyMediaPlayer,
  368.                      Created = May(),
  369.                      CreatedBy = Users.DeveloperDeborah,
  370.                      Summary = "UI turns black and white when playing old films",
  371.                      Severity = Severity.Minor,
  372.                      AssignedTo = Users.TesterTara,
  373.                      Status = Status.Fixed,
  374.                      LastModified = May()
  375.                  },
  376.  
  377.                  new Defect
  378.                  {
  379.                      Project = Projects.SkeetyTalk,
  380.                      Created = May(),
  381.                      CreatedBy = Users.ManagerMary,
  382.                      Summary = "Password reset changes passwords for all users",
  383.                      Severity = Severity.Showstopper,
  384.                      AssignedTo = null,
  385.                      Status = Status.Closed,
  386.                      LastModified = May()
  387.                  },
  388.  
  389.                  new Defect
  390.                  {
  391.                      Project = Projects.SkeetyMediaPlayer,
  392.                      Created = May(),
  393.                      CreatedBy = Users.TesterTim,
  394.                      Summary = "Modern music sounds rubbish",
  395.                      Severity = Severity.Trivial,
  396.                      AssignedTo = Users.DeveloperDarren,
  397.                      Status = Status.Created,
  398.                      LastModified = May()
  399.                  },
  400.  
  401.                  new Defect
  402.                  {
  403.                      Project = Projects.SkeetyTalk,
  404.                      Created = May(),
  405.                      CreatedBy = Users.TesterTim,
  406.                      Summary = "Webcam makes me look bald",
  407.                      Severity = Severity.Showstopper,
  408.                      AssignedTo = Users.TesterTim,
  409.                      Status = Status.Fixed,
  410.                      LastModified = May()
  411.                  },
  412.  
  413.                  new Defect
  414.                  {
  415.                      Project = Projects.SkeetyTalk,
  416.                      Created = May(),
  417.                      CreatedBy = Users.CustomerColin,
  418.                      Summary = "Sound is distorted when speakers are underwater",
  419.                      Severity = Severity.Major,
  420.                      AssignedTo = Users.DeveloperDarren,
  421.                      Status = Status.Created,
  422.                      LastModified = May()
  423.                  },
  424.  
  425.                  new Defect
  426.                  {
  427.                      Project = Projects.SkeetyTalk,
  428.                      Created = May(),
  429.                      CreatedBy = Users.DeveloperDarren,
  430.                      Summary = "Japanese characters don't display properly",
  431.                      Severity = Severity.Major,
  432.                      AssignedTo = Users.DeveloperDeborah,
  433.                      Status = Status.Accepted,
  434.                      LastModified = May()
  435.                  },
  436.  
  437.                  new Defect
  438.                  {
  439.                      Project = Projects.SkeetyMediaPlayer,
  440.                      Created = May(),
  441.                      CreatedBy = Users.TesterTara,
  442.                      Summary = "Video takes 100% of CPU",
  443.                      Severity = Severity.Major,
  444.                      AssignedTo = Users.DeveloperDeborah,
  445.                      Status = Status.Accepted,
  446.                      LastModified = May()
  447.                  },
  448.  
  449.                  new Defect
  450.                  {
  451.                      Project = Projects.SkeetyMediaPlayer,
  452.                      Created = May(),
  453.                      CreatedBy = Users.TesterTim,
  454.                      Summary = "DVD Easter eggs unavailable",
  455.                      Severity = Severity.Trivial,
  456.                      AssignedTo = Users.DeveloperDarren,
  457.                      Status = Status.Created,
  458.                      LastModified = May()
  459.                  },
  460.  
  461.                  new Defect
  462.                  {
  463.                      Project = Projects.SkeetyTalk,
  464.                      Created = May(),
  465.                      CreatedBy = Users.ManagerMary,
  466.                      Summary = "Transparency is high for menus to be readable",
  467.                      Severity = Severity.Minor,
  468.                      AssignedTo = Users.DeveloperDeborah,
  469.                      Status = Status.Accepted,
  470.                      LastModified = May()
  471.                  },
  472.  
  473.                  new Defect
  474.                  {
  475.                      Project = Projects.SkeetyMediaPlayer,
  476.                      Created = May(),
  477.                      CreatedBy = Users.CustomerColin,
  478.                      Summary = "About box is missing version number",
  479.                      Severity = Severity.Minor,
  480.                      AssignedTo = Users.CustomerColin,
  481.                      Status = Status.Fixed,
  482.                      LastModified = May()
  483.                  },
  484.  
  485.                  new Defect
  486.                  {
  487.                      Project = Projects.SkeetyTalk,
  488.                      Created = May(),
  489.                      CreatedBy = Users.TesterTim,
  490.                      Summary = "Logs record confidential conversations",
  491.                      Severity = Severity.Major,
  492.                      AssignedTo = Users.DeveloperDarren,
  493.                      Status = Status.Reopened,
  494.                      LastModified = May()
  495.                  },
  496.  
  497.                  new Defect
  498.                  {
  499.                      Project = Projects.SkeetyTalk,
  500.                      Created = May(),
  501.                      CreatedBy = Users.DeveloperDeborah,
  502.                      Summary = "Profanity filter is too aggressive",
  503.                      Severity = Severity.Minor,
  504.                      AssignedTo = Users.TesterTara,
  505.                      Status = Status.Fixed,
  506.                      LastModified = May()
  507.                  },
  508.  
  509.                  new Defect
  510.                  {
  511.                      Project = Projects.SkeetyMediaPlayer,
  512.                      Created = May(),
  513.                      CreatedBy = Users.TesterTara,
  514.                      Summary = "Full screen mode fails on dual monitors",
  515.                      Severity = Severity.Minor,
  516.                      AssignedTo = Users.DeveloperDeborah,
  517.                      Status = Status.Created,
  518.                      LastModified = May()
  519.                  },
  520.  
  521.                  new Defect
  522.                  {
  523.                      Project = Projects.SkeetyMediaPlayer,
  524.                      Created = May(),
  525.                      CreatedBy = Users.CustomerColin,
  526.                      Summary = "Visualization hypnotises pets",
  527.                      Severity = Severity.Minor,
  528.                      AssignedTo = Users.DeveloperDeborah,
  529.                      Status = Status.Accepted,
  530.                      LastModified = May()
  531.                  },
  532.  
  533.                  new Defect
  534.                  {
  535.                      Project = Projects.SkeetyTalk,
  536.                      Created = May(),
  537.                      CreatedBy = Users.ManagerMary,
  538.                      Summary = "Resizing while typing loses input",
  539.                      Severity = Severity.Trivial,
  540.                      AssignedTo = Users.DeveloperDarren,
  541.                      Status = Status.Created,
  542.                      LastModified = May()
  543.                  },
  544.  
  545.                  new Defect
  546.                  {
  547.                      Project = Projects.SkeetyMediaPlayer,
  548.                      Created = May(),
  549.                      CreatedBy = Users.TesterTim,
  550.                      Summary = "Network is saturated when playing WAV file",
  551.                      Severity = Severity.Minor,
  552.                      AssignedTo = Users.TesterTim,
  553.                      Status = Status.Fixed,
  554.                      LastModified = May()
  555.                  },
  556.  
  557.                  new Defect
  558.                  {
  559.                      Project = Projects.SkeetyMediaPlayer,
  560.                      Created = May(),
  561.                      CreatedBy = Users.TesterTara,
  562.                      Summary = "Media library tells user to keep the noise down",
  563.                      Severity = Severity.Major,
  564.                      AssignedTo = Users.DeveloperDarren,
  565.                      Status = Status.Created,
  566.                      LastModified = May()
  567.                  }
  568.              };
  569.          }
  570.  
  571.          public static DateTime May(int day)
  572.          {
  573.              return new DateTime(, , day);
  574.          }
  575.  
  576.      }
  577.      public enum UserType : byte
  578.      {
  579.          Customer,
  580.          Developer,
  581.          Tester,
  582.          Manager,
  583.      }
  584.      public class Defect
  585.      {
  586.          public Project Project { get; set; }
  587.          /// <summary>
  588.          /// Which user is this defect currently assigned to? Should not be null until the status is Closed.
  589.          /// </summary>
  590.          public User AssignedTo { get; set; }
  591.          public string Summary { get; set; }
  592.          public Severity Severity { get; set; }
  593.          public Status Status { get; set; }
  594.          public DateTime Created { get; set; }
  595.          public DateTime LastModified { get; set; }
  596.          public User CreatedBy { get; set; }
  597.          public int ID { get; private set; }
  598.  
  599.          public Defect()
  600.          {
  601.              ID = StaticCounter.Next();
  602.          }
  603.  
  604.          public override string ToString()
  605.          {
  606.              return string.Format("{0,2}: {1}\r\n    ({2:d}-{3:d}, {4}/{5}, {6} -> {7})",
  607.                  ID, Summary, Created, LastModified, Severity, Status, CreatedBy.Name,
  608.                  AssignedTo == null ? "n/a" : AssignedTo.Name);
  609.          }
  610.      }
  611.      public class NotificationSubscription
  612.      {
  613.          /// <summary>
  614.          /// Project for which this subscriber is notified
  615.          /// </summary>
  616.          public Project Project { get; set; }
  617.  
  618.          /// <summary>
  619.          /// The address to send the notification to
  620.          /// </summary>
  621.          public string EmailAddress { get; set; }
  622.      }
  623.      public class Project
  624.      {
  625.          public string Name { get; set; }
  626.  
  627.          public override string ToString()
  628.          {
  629.              return string.Format("Project: {0}", Name);
  630.          }
  631.      }
  632.      public enum Severity : byte
  633.      {
  634.          Trivial,
  635.          Minor,
  636.          Major,
  637.          Showstopper,
  638.      }
  639.      public static class StaticCounter
  640.      {
  641.          static int next = ;
  642.          public static int Next()
  643.          {
  644.              return next++;
  645.          }
  646.      }
  647.      public enum Status : byte
  648.      {
  649.          /// <summary>
  650.          /// Defect has been opened, but not verified as reproducible or an issue.
  651.          /// </summary>
  652.          Created,
  653.          /// <summary>
  654.          /// Defect has been verified as an issue requiring work.
  655.          /// </summary>
  656.          Accepted,
  657.          /// <summary>
  658.          /// Defect has been fixed in code, but not verified other than through developer testing.
  659.          /// </summary>
  660.          Fixed,
  661.          /// <summary>
  662.          /// Defect was fixed, but has now been reopened due to failing verification.
  663.          /// </summary>
  664.          Reopened,
  665.          /// <summary>
  666.          /// Defect has been fixed and tested; the fix is satisfactory.
  667.          /// </summary>
  668.          Closed,
  669.      }
  670.      public class User
  671.      {
  672.          public string Name { get; set; }
  673.          public UserType UserType { get; set; }
  674.  
  675.          public User(string name, UserType userType)
  676.          {
  677.              Name = name;
  678.              UserType = userType;
  679.          }
  680.  
  681.          public override string ToString()
  682.          {
  683.              return string.Format("User: {0} ({1})", Name, UserType);
  684.          }
  685.      }
  686.      static class Extensions
  687.      {
  688.          public static Dummy<T> Where<T>(this Dummy<T> dummy,
  689.                                          Func<T, bool> predicate)
  690.          {
  691.              Console.WriteLine("Where called");
  692.              return dummy;
  693.          }
  694.      }
  695.      class Dummy<T>
  696.      {
  697.          public Dummy<U> Select<U>(Func<T, U> selector)
  698.          {
  699.              Console.WriteLine("Select called");
  700.              return new Dummy<U>();
  701.          }
  702.      }
  703.      public class DateTimeRange : IEnumerable<DateTime>
  704.      {
  705.          private readonly DateTime start;
  706.          private readonly DateTime end;
  707.  
  708.          public DateTimeRange(DateTime start, DateTime end)
  709.          {
  710.              this.start = start;
  711.              this.end = end;
  712.          }
  713.  
  714.          public IEnumerator<DateTime> GetEnumerator()
  715.          {
  716.              for (DateTime current = start; current <= end; current = current.AddDays())
  717.              {
  718.                  yield return current;
  719.              }
  720.          }
  721.  
  722.          IEnumerator IEnumerable.GetEnumerator()
  723.          {
  724.              return GetEnumerator();
  725.          }
  726.      }

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