LINQ GroupBy Usage - vb.net

Question

I am using this to get all my records ordered by date:
Dim myData = db.Tbl_Exercises.Where(Function(x) x.Exercise_Employee_ID).OrderBy(Function(x) x.Exercise_Create_Date)
I loop through with this:
For Each i As Tbl_Exercise In myData
data.Add(New Object() {i.Tbl_Exercise_Type.ExType_Desc, i.Exercise_Duration})
Next
How can I group by i.Tbl_Exercise_Type.ExType_Desc so I don't have duplicates?
I tried this:
Dim myData = db.Tbl_Exercises.Where(Function(x) x.Exercise_Employee_ID).GroupBy(Function(x) x.Exercise_Type_ID)
But, I don't know how to access the variables within my loop.
Thank you.
Edit:
<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
Edit:
' 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

Note: Your example isn't entirely clear, so I'm going to make a few assumptions about what you are trying to do with my solution. I'll modify it as needed as more details are made available.
From what it looks like, for each employee you are trying to get a collection of types of exercise that they have performed, and with each type of exercise you would also like a collection of the lengths of time that they spent performing these activities.
I'm going to assume that a row in Tbl_Exercises looks like this:
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
The attempt you make at the end is pretty close, you just need to actually use the grouping once you've created it.
What the GroupBy method has returned you here is actually an IGrouping(Of Integer, Tbl_Exercise) where the key is the Exercise_Type_ID and the value is a collection of rows that are grouped by the key. To access them its pretty simple, you just have to think of the groupings as a sort of nested collection:
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
Obviously, you may want to do something different than print out individual collections, you may want to data bind each grouping to their own DataGrid so that you can display them separately. You may want to sort each grouping by date, or you may only want the first element from each group. Once you understand how the groupings are structured, it should be pretty easy to accomplish exactly what you're looking for.
Edit:
If you're just looking to aggregate some field in the grouping, this is very simple to accomplish without needing to resort to looping over the results. Simply adding a call to Select on top of your GroupBy will let you project the results into your desired aggregate form:
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)