Use LINQ to convert multiple dates into ranges - asp.net

Question

I need help applying settings across a calendar year. My users are entering numerical targets into a database according to the season in a calendar. Think, apple cider will sell higher during the fall (September through November) and less during the rest of the year (December through August). However, apple juice sells evenly throughout the year.
To simplify data entry for my users, they enter a target sales number along with the month that number will start for each product.
For example, the data in the database will look like this (There are a max of two targets for any product):
Apple Cider - September - 5,000 gallons
Apple Cider - December - 1,000 gallons
Apple Juice - September - 3,000 gallons
I also have our fiscal calendar in a database table, so I know what fiscal year, month, number of weeks in the month, etc. are associated with any day.
I need to apply this data to a report, but I need data for every month in the year, not just what the user has entered.
I'm having trouble using LINQ to join to my fiscal calendar to create an exploded view of the data? How can I start with a list of all months in the year, for each product, place the targets in the calendar, then fill in the blanks. For example for Apple Cider using the example above
January
February
March
April
May
June
July
August
September - 5,000 gallonws
October
November
December - 1,000 gallons
Apple Cider - September - 5,000 gallons
Apple Cider - October - 5,000 gallons
Apple Cider - November - 5,000 gallons
Apple Cider - December - 1,000 gallons
Apple Cider - January - 1,000 gallons
Apple Cider - February- 1,000 gallons
Apple Cider - March - 1,000 gallons
Apple Cider - April- 1,000 gallons
Apple Cider - May - 1,000 gallons
Apple Cider - June - 1,000 gallons
Apple Cider - July - 1,000 gallons
Apple Cider - August - 1,000 gallons
Apple Juice - September - 3,000 gallons
Apple Juice - October - 3,000 gallons
Apple Juice - November - 3,000 gallons
Apple Juice - December - 3,000 gallons
Apple Juice - January - 3,000 gallons
Apple Juice - February - 3,000 gallons
Apple Juice - March - 3,000 gallons
Apple Juice - April - 3,000 gallons
Apple Juice - May - 3,000 gallons
Apple Juice - June - 3,000 gallons
Apple Juice - July - 3,000 gallons
Apple Juice - August - 3,000 gallons

Answer 1

I'm not sure how much help LINQ would be in this scenario.
You can achieve the required transformation relatively simply with a for loop:
' Sample data using anonymous types
Dim entries() =
{New With {.Name = "Apple Cider", .Year = 2012, .Month = 9, .Quantity = 5000},
New With {.Name = "Apple Cider", .Year = 2012, .Month = 12, .Quantity = 1000},
New With {.Name = "Apple Juice", .Year = 2013, .Month = 9, .Quantity = 3000}}
' Dictionary keyed by date
Dim dict = entries.ToDictionary( _
Function(entry) New DateTime(entry.Year, entry.Month, 1))
' Current is first entry
Dim currentEntry = entries(0)
Dim epoch = New DateTime(currentEntry.Year, currentEntry.Month, 1)
' Iterate over 24 months
For i = 0 To 23
Dim currentMonth = epoch.AddMonths(i)
' Update current based on current month
If dict.ContainsKey(currentMonth) Then
currentEntry = dict(currentMonth)
End If
' Write data
Console.WriteLine("{0} - {1} - {2} gallons",
currentEntry.Name,
MonthName(currentMonth.Month),
currentEntry.Quantity)
Next

Answer 2

To do this with Linq use Range() (in cases where something can be done in a loop often range can be substituted.)
Here is an example using Enumerable.Range and #PhillipTrelford's example data:
Sub Main
Dim entries() = {New With {.Name = "Apple Cider", .Year = 2012, .Month = 9, .Quantity = 5000}, _
New With {.Name = "Apple Cider", .Year = 2012, .Month = 12, .Quantity = 1000}, _
New With {.Name = "Apple Juice", .Year = 2013, .Month = 9, .Quantity = 3000}}
Dim dict = entries.ToDictionary( Function(entry) New DateTime(entry.Year, entry.Month, 1))
Dim startDate as DateTime = New DateTime(2012,9,1)
Dim curDefault = New With {.Name = "", .Quantity = 0}
Dim result = Enumerable.Range(0, 24).Select(Function(x)
Dim thisdate = startDate.AddMonths(x)
If dict.ContainsKey(thisdate) Then
curDefault.Name = dict(thisdate).Name
curDefault.Quantity = dict(thisdate).Quantity
End If
Return String.Format("{0} - {1} - {2} gallons",curDefault.Name,thisdate.ToString("MMMM"),curDefault.Quantity)
End Function)
result.Dump
End Sub
This code runs just fine and give expected results using linqpad (see linqpad.com)
Apple Cider - September - 5000 gallons
Apple Cider - October - 5000 gallons
Apple Cider - November - 5000 gallons
Apple Cider - December - 1000 gallons
Apple Cider - January - 1000 gallons
Apple Cider - February - 1000 gallons
Apple Cider - March - 1000 gallons
Apple Cider - April - 1000 gallons
Apple Cider - May - 1000 gallons
Apple Cider - June - 1000 gallons
Apple Cider - July - 1000 gallons
Apple Cider - August - 1000 gallons
Apple Juice - September - 3000 gallons
Apple Juice - October - 3000 gallons
Apple Juice - November - 3000 gallons
Apple Juice - December - 3000 gallons
Apple Juice - January - 3000 gallons
Apple Juice - February - 3000 gallons
Apple Juice - March - 3000 gallons
Apple Juice - April - 3000 gallons
Apple Juice - May - 3000 gallons
Apple Juice - June - 3000 gallons
Apple Juice - July - 3000 gallons
Apple Juice - August - 3000 gallons