class DefectsOpenedByDate
{ static void Main() //使用join...into子句进行分组连接 累计计算五月份每一天缺陷的数目
{
var dates = new DateTimeRange(SampleData.Start, SampleData.End);
//{Chapter11.Queries.DateTimeRange} //这句调用了SampleData的构造函数
var query = from date in dates
join defect in SampleData.AllDefects
on date equals defect.Created.Date
//defect 这句没有跳转到其他语句，这是个匿名方法
//{ 1: MP3 files crash system (2013/5/1-2013/5/23, Showstopper/Accepted, Tim Trotter -> Darren Dahlia)}
//{ 2: Text is too big(2013/5/3-2013/5/9, Trivial/Closed, Deborah Denton -> n/a)}
//{ 3: Sky is wrong shade of blue (2013/5/3-2013/5/19, Minor/Fixed, Colin Carton -> Tara Tutu)}
//{ 4: Can't play files more than 200 bytes long (2013/5/4-2013/5/23, Major/Reopened, Darren Dahlia -> Darren Dahlia)}
//{ 5: Installation is slow (2013/5/6-2013/5/15, Trivial/Fixed, Tim Trotter -> Tim Trotter)}
//{ 6: DivX is choppy on Pentium 100 (2013/5/7-2013/5/29, Major/Accepted, Mary Malcop -> Darren Dahlia)}
//{ 7: Client acts as virus (2013/5/8-2013/5/10, Showstopper/Closed, Deborah Denton -> n/a)}
//{ 8: Subtitles only work in Welsh(2013/5/8-2013/5/23, Major/Fixed, Darren Dahlia -> Tim Trotter)}
//{ 9: Voice recognition is confused by background noise (2013/5/9-2013/5/15, Minor/Closed, Colin Carton -> n/a)}
//{10: User interface should be more caramelly (2013/5/9-2013/5/9, Trivial/Created, Tim Trotter -> Darren Dahlia)}
//{11: Burning a CD makes the printer catch fire (2013/5/10-2013/5/29, Showstopper/Closed, Mary Malcop -> n/a)}
//{12: Peer to peer pairing passes parameters poorly (2013/5/10-2013/5/12, Minor/Accepted, Tara Tutu -> Darren Dahlia)}
//{13: Delay when sending message (2013/5/11-2013/5/20, Minor/Fixed, Darren Dahlia -> Tara Tutu)}
//{14: Volume control needs to go to 11 (2013/5/11-2013/5/11, Minor/Created, Mary Malcop -> Darren Dahlia)}
//{15: Splash screen fades too quickly (2013/5/11-2013/5/15, Minor/Fixed, Colin Carton -> Tara Tutu)}
//{16: Text box doesn't keep up with fast typing (2013/5/12-2013/5/12, Major/Accepted, Deborah Denton -> Deborah Denton)}
//{17: Password displayed in plain text (2013/5/12-2013/5/13, Showstopper/Closed, Darren Dahlia -> n/a)}
//{18: Play button points the wrong way (2013/5/12-2013/5/17, Major/Fixed, Tim Trotter -> Tim Trotter)}
//{19: Wizard needed for CD burning (2013/5/13-2013/5/20, Minor/Fixed, Colin Carton -> Colin Carton)}
//{20: Subtitles don't display during fast forward (2013/5/13-2013/5/14, Trivial/Accepted, Mary Malcop -> Darren Dahlia)}
//{21: Memory leak when watching Memento (2013/5/13-2013/5/13, Trivial/Created, Darren Dahlia -> Deborah Denton)}
//{22: Profile screen shows login count of -1 (2013/5/13-2013/5/20, Major/Accepted, Deborah Denton -> Deborah Denton)}
//{23: Server crashes under heavy load (3 users) (2013/5/13-2013/5/17, Major/Accepted, Tim Trotter -> Deborah Denton)}
//{24: Unable to connect to any media server (2013/5/15-2013/5/18, Showstopper/Reopened, Tara Tutu -> Darren Dahlia)}
//{25: UI turns black and white when playing old films (2013/5/15-2013/5/25, Minor/Fixed, Deborah Denton -> Tara Tutu)}
//{26: Password reset changes passwords for all users (2013/5/16-2013/5/18, Showstopper/Closed, Mary Malcop -> n/a)}
//{27: Modern music sounds rubbish (2013/5/17-2013/5/17, Trivial/Created, Tim Trotter -> Darren Dahlia)}
//{28: Webcam makes me look bald (2013/5/18-2013/5/27, Showstopper/Fixed, Tim Trotter -> Tim Trotter)}
//{29: Sound is distorted when speakers are underwater (2013/5/18-2013/5/18, Major/Created, Colin Carton -> Darren Dahlia)}
//{30: Japanese characters don't display properly (2013/5/19-2013/5/23, Major/Accepted, Darren Dahlia -> Deborah Denton)}
//{31: Video takes 100% of CPU (2013/5/20-2013/5/22, Major/Accepted, Tara Tutu -> Deborah Denton)}
//{32: DVD Easter eggs unavailable (2013/5/22-2013/5/22, Trivial/Created, Tim Trotter -> Darren Dahlia)}
//{33: Transparency is high for menus to be readable (2013/5/23-2013/5/25, Minor/Accepted, Mary Malcop -> Deborah Denton)}
//{34: About box is missing version number (2013/5/24-2013/5/29, Minor/Fixed, Colin Carton -> Colin Carton)}
//{35: Logs record confidential conversations (2013/5/25-2013/5/30, Major/Reopened, Tim Trotter -> Darren Dahlia)}
//{36: Profanity filter is too aggressive (2013/5/27-2013/5/29, Minor/Fixed, Deborah Denton -> Tara Tutu)}
//{37: Full screen mode fails on dual monitors (2013/5/27-2013/5/27, Minor/Created, Tara Tutu -> Deborah Denton)}
//{38: Visualization hypnotises pets (2013/5/28-2013/5/29, Minor/Accepted, Colin Carton -> Deborah Denton)}
//{39: Resizing while typing loses input (2013/5/29-2013/5/29, Trivial/Created, Mary Malcop -> Darren Dahlia)}
//{40: Network is saturated when playing WAV file (2013/5/30-2013/5/31, Minor/Fixed, Tim Trotter -> Tim Trotter)}
//{41: Media library tells user to keep the noise down (2013/5/31-2013/5/31, Major/Created, Tara Tutu -> Darren Dahlia)}
//跳转到public IEnumerator<DateTime> GetEnumerator() 方法
into joined
select new { Date=date, Count=joined.Count() };
//query
//{System.Linq.Enumerable.GroupJoinIterator<System.DateTime,Chapter11.Model.Defect,System.DateTime,<>f__AnonymousType9<System.DateTime,int>>}
foreach (var grouped in query)//in 会执行public IEnumerator<DateTime> GetEnumerator()
//grouped { Date = {2013/5/1 0:00:00}, Count = 1 }
//{ Date = {2013/5/2 0:00:00}, Count = 0 }
//{ Date = {2013/5/3 0:00:00}, Count = 2 }
//{ Date = {2013/5/4 0:00:00}, Count = 1 }
//{ Date = {2013/5/5 0:00:00}, Count = 0 }
//{ Date = {2013/5/6 0:00:00}, Count = 1 }
//{ Date = {2013/5/7 0:00:00}, Count = 1 }
//{ Date = {2013/5/8 0:00:00}, Count = 2 }
//{ Date = {2013/5/9 0:00:00}, Count = 2 }
//{ Date = {2013/5/10 0:00:00}, Count = 2 }
//{ Date = {2013/5/11 0:00:00}, Count = 3 }
//{ Date = {2013/5/12 0:00:00}, Count = 3 }
//{ Date = {2013/5/13 0:00:00}, Count = 5 }
//{ Date = {2013/5/14 0:00:00}, Count = 0 }
//{ Date = {2013/5/15 0:00:00}, Count = 2 }
//{ Date = {2013/5/16 0:00:00}, Count = 1 }
//{ Date = {2013/5/17 0:00:00}, Count = 1 }
//{ Date = {2013/5/18 0:00:00}, Count = 2 }
//{ Date = {2013/5/19 0:00:00}, Count = 1 }
//{ Date = {2013/5/20 0:00:00}, Count = 1 }
//{ Date = {2013/5/21 0:00:00}, Count = 0 }
//{ Date = {2013/5/22 0:00:00}, Count = 1 }
//{ Date = {2013/5/23 0:00:00}, Count = 1 }
//{ Date = {2013/5/24 0:00:00}, Count = 1 }
//{ Date = {2013/5/25 0:00:00}, Count = 1 }
//{ Date = {2013/5/26 0:00:00}, Count = 0 }
//{ Date = {2013/5/27 0:00:00}, Count = 2 }
//{ Date = {2013/5/28 0:00:00}, Count = 1 }
//{ Date = {2013/5/29 0:00:00}, Count = 1 }
//{ Date = {2013/5/30 0:00:00}, Count = 1 }
//{ Date = {2013/5/31 0:00:00}, Count = 1 }
{
Console.WriteLine("{0:d}: {1}", grouped.Date, grouped.Count);
}
}
}
public class SampleData
{
public static readonly DateTime Start = May(1);
public static readonly DateTime End = May(31);
public static DateTime May(int day)
{
return new DateTime(2013, 5, day);
}
static SampleData()
{
projects = new List<Project>
{
Projects.SkeetyMediaPlayer,
Projects.SkeetyTalk,
Projects.SkeetyOffice
};
users = new List<User>
{
Users.TesterTim,
Users.TesterTara,
Users.DeveloperDeborah,
Users.DeveloperDarren,
Users.ManagerMary,
Users.CustomerColin
};
subscriptions = new List<NotificationSubscription>
{
new NotificationSubscription { Project=Projects.SkeetyMediaPlayer, EmailAddress="[email protected]" },
new NotificationSubscription { Project=Projects.SkeetyTalk, EmailAddress="[email protected]" },
new NotificationSubscription { Project=Projects.SkeetyOffice, EmailAddress="[email protected]" },
new NotificationSubscription { Project=Projects.SkeetyMediaPlayer, EmailAddress="[email protected]"}
};
//41个缺陷不贴代码
defects = new List<Defect>
{
new Defect
{
Project = Projects.SkeetyMediaPlayer,
Created = May(1),
CreatedBy = Users.TesterTim,
Summary = "MP3 files crash system",
Severity = Severity.Showstopper,
AssignedTo = Users.DeveloperDarren,
Status = Status.Accepted,
LastModified = May(23)
},
};
}
public static DateTime May(int day)//把day带进去 看缺陷的May的参数
{
return new DateTime(2013, 5, day);
}
}
public class Defect
{
public Defect()
{
ID = StaticCounter.Next();
}
}
public static class StaticCounter
{
static int next = 1;
public static int Next()
{
return next++;
}
}
public class DateTimeRange : IEnumerable<DateTime>
{
private readonly DateTime start;
private readonly DateTime end;
public DateTimeRange(DateTime start, DateTime end)
//start{2013/5/1 0:00:00} end{2013/5/31 0:00:00}
{
this.start = start;
this.end = end;
}
public IEnumerator<DateTime> GetEnumerator()
{
for (DateTime current = start; current <= end; current = current.AddDays(1))
//current {2013/5/1 0:00:00}
{
yield return current;//返回到 on date equals defect.Created.Date
}
}
IEnumerator IEnumerable.GetEnumerator()
{
return GetEnumerator();
}
}
没有贴出所有代码，原有的代码太长了。还隐藏了一些细节，缺陷就有41条
Count()本身使用立即执行的模式，就是遍历它被调用的序列中的所有元素，不过我们只能在
表达式的投影部分调用它，所以它就成为Lambda表达式的一部分。这意味着，依然可以实现
延迟执行:直到开始执行foreach循环才会进行求值。
编译器将分组连接转译为简单地调用GroupJoin方法，就像Join一样。
同内连接一致，如果分组连接后面紧跟着select子句，那么投影就用作GroupJoin调用的结果
选择器，否则，就引入一个透明标识符。
输出
2013/5/1: 1
2013/5/2: 0
2013/5/3: 2
2013/5/4: 1
2013/5/5: 0
2013/5/6: 1
2013/5/7: 1
2013/5/8: 2
2013/5/9: 2
2013/5/10: 2
2013/5/11: 3
2013/5/12: 3
2013/5/13: 5
2013/5/14: 0
2013/5/15: 2
2013/5/16: 1
2013/5/17: 1
2013/5/18: 2
2013/5/19: 1
2013/5/20: 1
2013/5/21: 0
2013/5/22: 1
2013/5/23: 1
2013/5/24: 1
2013/5/25: 1
2013/5/26: 0
2013/5/27: 2
2013/5/28: 1
2013/5/29: 1
2013/5/30: 1
2013/5/31: 1