需要使用计数返回GroupBy数据但是使用LINQ选择多个字段

Question

好吧，我确定这对某人来说很简单，但它开始让我撕掉我的听力，所以如果这看起来像一个简单的问题，我会事先道歉：

我有以下课程：

Public Class Ticket
    Public Property ticket_id As String
    Public Property ticket_assignee As String
    Public Property ticket_email As String
End Class

我正在尝试使用LINQ按ticket_email字段对列表进行分组，但允许我获取每个组的ticket_assignee字段和计数。

例如：

对于每个电子邮件地址，请返回受让人姓名以及该电子邮件组中的票数，如下所示：

'fred@someplace.com' = Fred, 4
'joe@someplace.com' = Joe, 2
'bob@someplace.com' = Bob, 8

等...

我仍然试图了解LINQ，并希望更多地了解它。任何帮助将不胜感激。

Answer 1

            Dim tickets As New List(Of Ticket)
            For i = 1 To 3
                tickets.Add(New Ticket With {.ticket_id = i.ToString, .ticket_email = "a", .ticket_assignee = "me"})
            Next
            For i = 4 To 6
                tickets.Add(New Ticket With {.ticket_id = i.ToString, .ticket_email = "b", .ticket_assignee = "me2"})
            Next

            Dim group = tickets.GroupBy(Function(x) x.ticket_assignee).Select(Function(y) New Tuple(Of String, Integer)(y.First.ticket_assignee, y.Count))

Answer 2

查询语法解决方案：

Sub Main
    Dim q = from entry in Ticket.GetTickets
            group entry by entry.ticket_assignee Into NewGroup = Group, Count()
            select new with{
            .Assignee = NewGroup.Select(function(x) x.ticket_assignee).First,
            .Email = NewGroup.Select(function(x) x.ticket_email).First,
            .Count = Count}
    'q.dump()
End Sub
' Define other methods and classes here
Public Class Ticket
    Public Property ticket_id As Integer
    Public Property ticket_assignee As String
    Public Property ticket_email As String

    Public Shared Function GetTickets as list(of Ticket)

    Return New List(of Ticket) From {New Ticket With {.ticket_id = 1, .ticket_assignee = "Fred", .ticket_email = "fred@ticket.de"},
    New Ticket With {.ticket_id = 2, .ticket_assignee = "Fred", .ticket_email = "fred@ticket.de"},
    New Ticket With {.ticket_id = 3, .ticket_assignee = "Fred", .ticket_email = "fred@ticket.de"},
    New Ticket With {.ticket_id = 4, .ticket_assignee = "Anna", .ticket_email = "Anna@ticket.de"},
    New Ticket With {.ticket_id = 5, .ticket_assignee = "Anna", .ticket_email = "Anna@ticket.de"},
    New Ticket With {.ticket_id = 6, .ticket_assignee = "Jack", .ticket_email = "Jack@ticket.de"}}
    End Function
End Class

给你：

为了学习Linq，我强烈推荐LinqPad。您可以选择VB.NET程序，复制我的代码，取消注释.dump（）行并运行它。