I need to get the number of Tasks in a project for the MaxValue property of Telerik ProgressBar and the numbers of completed tasks for its Value property. Below are the codes I used:

Public Sub progressBar()
Dim projectID As String = Me.txtID.Text
Dim db As New ProjectsEntities()
Dim totalTasks = Aggregate task In db.tblTasks
Where task.ProjectID = projectID
Into Count()
Dim totalTasksCompleted = Aggregate task In db.tblTasks
Where task.ProjectID = projectID And 
task.TaskStatus = "Completed"
Into Count()
Me.TaskProgressBar.Value = totalTasksCompleted
Me.TaskProgressBar.MaxValue = totalTasks
Me.TaskProgressBar.ChunksCount = totalTasks
End Sub

For Average and Sum, below are codes copied from Microsoft Site.

Dim averageOrderCount = Aggregate cust In db.Customers
                        Where cust.City = "London"
                        Into Average(cust.Orders.Count)
msg &= "Average number of Orders per customer: " &
       averageOrderCount & vbCrLf

Dim venezuelaTotalOrders = Aggregate cust In db.Customers
                           Where cust.Country = "Venezuela"
                           Into Sum(cust.Orders.Count)
msg &= "Total number of orders from Customers in 
       Venezuela: " & venezuelaTotalOrders & vbCrLf

MsgBox(msg)

Dim averageCustomersByCity = From cust In db.Customers
                             Group By cust.City
                             Into Average(cust.Orders.Count)
                             Order By Average