Question

我用它来按日期排序我的所有记录：

Dim myData = db.Tbl_Exercises.Where(Function(x) x.Exercise_Employee_ID).OrderBy(Function(x) x.Exercise_Create_Date)

我循环使用：

    For Each i As Tbl_Exercise In myData

        data.Add(New Object() {i.Tbl_Exercise_Type.ExType_Desc, i.Exercise_Duration})

    Next

如何按i.Tbl_Exercise_Type.ExType_Desc进行分组，以便我没有重复项？

我试过了：

Dim myData = db.Tbl_Exercises.Where(Function(x) x.Exercise_Employee_ID).GroupBy(Function(x) x.Exercise_Type_ID)

但是，我不知道如何在我的循环中访问变量。

谢谢。

修改

<EmployeeAuthorize()>
Function ExercisePieChartData() As JsonResult

    ' get current employee's id
    Dim db1 As EmployeeDbContext = New EmployeeDbContext
    Dim user1 = db1.Tbl_Employees.Where(Function(e) e.Employee_EmailAddress = User.Identity.Name).Single()
    Dim empId = user1.Employee_ID

    Dim activityGroups = db.Tbl_Exercises.Where(Function(x) x.Exercise_Employee_ID = empId).GroupBy(Function(x) x.Exercise_Type_ID)

    Dim data = New List(Of Object)

    ' columns (headers)
    data.Add(New Object() {"Type", "Duration"})

    ' Iterate through each collection of activities, grouped by activity types
    For Each group In activityGroups

        ' Iterate through each Tbl_Exercise in the group
        For Each activity In group

            ' Do something with an individual element
            data.Add(New Object() {activity.Tbl_Exercise_Type.ExType_Desc, activity.Exercise_Duration})

        Next

    Next

    Return Json(data, JsonRequestBehavior.AllowGet)

End Function

修改

    ' Iterate through each collection of activities, grouped by activity types
    For Each group In activityGroups

        Dim type = ""
        Dim duration = 0

        ' Iterate through each Tbl_Exercise in the group
        For Each activity In group

            ' Do something with an individual element
            type = activity.Tbl_Exercise_Type.ExType_Desc
            duration += activity.Exercise_Duration

        Next

        data.Add(New Object() {type, duration})

    Next

Answer 1

注意：您的示例并不完全清楚，因此我将对您尝试使用我的解决方案进行一些假设。我会根据需要修改它，因为有更多细节可供使用。

从它看起来，对于每个员工，你试图获得他们已经完成的运动类型的集合，并且对于每种类型的运动，你还需要他们花费在执行这些运动上的时间长度的集合。活动。

我将假设Tbl_Exercises中的一行看起来像这样：

Public Class Tbl_Exercise

    Public Property Exercise_Employee_ID As Integer
    Public Property Exercise_Type_ID As Integer
    Public Property Exercise_Type_Desc As String
    Public Property Exercise_Duration As Integer

End Class

你在最后做的尝试非常接近，你只需要在创建后实际使用分组。

此处GroupBy方法返回的内容实际上是IGrouping(Of Integer, Tbl_Exercise)，其中键是Exercise_Type_ID，值是按键分组的行集合。要访问它们非常简单，您只需要将分组视为一种嵌套集合：

    Dim activityGroups = db.Tbl_Exercises.Where(Function(x) x.Exercise_Employee_ID = employeeId).GroupBy(Function(x) x.Exercise_Type_ID)

    ' Iterate through each collection of activities, grouped by activity types
    For Each group In activityGroups

        ' Iterate through each Tbl_Exercise in the group
        For Each activity In group

            ' Do something with an individual element
            Console.WriteLine(activity.Exercise_Duration)

        Next

    Next

显然，您可能希望执行与打印单个集合不同的操作，您可能希望将每个分组的数据绑定到它们自己的DataGrid，以便您可以单独显示它们。您可能希望按日期对每个分组进行排序，或者您可能只想要每个组中的第一个元素。一旦了解了分组的结构，就可以很容易地完成您正在寻找的内容。

修改

如果您只想在分组中聚合某些字段，则无需借助循环结果即可轻松完成。只需在Select之上添加对GroupBy的通话，您就可以将结果投影到所需的汇总表单中：

Dim data = db.Tbl_Exercises _ .Where(Function(x) x.Exercise_Employee_ID = empId) _ .GroupBy(Function(x) x.Exercise_Type_Desc) _ .Select(Function(x) Return New With { ' x.Key will give you access to the value that the grouping is grouped by .Exercise_Type_Desc = x.Key, .TotalDuration = x.Sum(Function(y) y.Exercise_Duration) } End Function)

LINQ GroupBy用法

1 个答案: