LINQ GroupBy month - linq

Question

I am having trouble getting an IQueryable list of a (subsonic) object grouped by Month and Year.
Basic view of the object...
public partial class DatabaseObject
{
[SubSonicPrimaryKey]
public int objectID { get; set; }
public string Description { get; set; }
public decimal Value { get; set; }
public string Category { get; set; }
public DateTime DateOccurred { get; set; }
}
Method to get IQueryable in my Database repository...
public IQueryable GetData(string DataType)
{
return (from t in db.All<DatabaseObject>()
orderby t.DateOccurred descending
select t)
.Where(e => e.Category == DataType);
}
My question is, how can I return the dates grouped by Month? I have tried the below, but this results in compiler warnings regarding anonymous types...
public IQueryable GetData(string DataType)
{
var datalist = (from t in db.All<FinancialTransaction>().Where(e => e.Category == DataType);
let m = new
{
month = t.DateOccurred.Month,
year = t.DateOccurred.Year
}
group t by m into l select new
{
Description = string.Format("{0}/{1}", l.Key.month, l.Key.year),
Value = l.Sum(v => v.Value), // Sum(v => v.Value),
Category = "Grouped"
DateOccurred = l.Last(v => v.DateOccurred)
}
return datalist;
}
Any ideas?

Answer 1

Try this couple issues i found, but you basically need to select a Database object versus anonymous type?
IQueryable<DatabaseObject> datalist = (
from t in db.All<FinancialTransaction>().Where(e => e.Category == DataType)
let m = new
{
month = t.DateOccurred.Month,
year = t.DateOccurred.Year
}
group t by m into l
select new DatabaseObject()
{
Description = string.Format("{0}/{1}", l.Key.month, l.Key.year),
Value = l.Sum(v => v.Value), //Sum(v => v.Value),
Category = "Grouped",
DateOccurred = l.Max(v => v.DateOccurred)
}).AsQueryable();
Let me know if my solution is now what you want. I also noticed you were using Last? The extension you were using I do not have so I replaced it with Max. I don't have subsonic installed so it might come with the libraries.

Answer 2

Any way don't combine LINQ in query syntax and LINQ in extension methods syntax. Use next:
from t in db.All<DatabaseObject>()
where e.Category equals DataType
orderby t.DateOccurred descending
select t;

Answer 3

The issue is apparantly to do with the way Subsonic interprests certain linq statements and is a known bug.
IEnumerable<DatabaseObject> datalist = (
from t in db.All<FinancialTransaction>().Where(e => e.Category == DataType).ToList()
let m = new
{
month = t.DateOccurred.Month,
year = t.DateOccurred.Year
}
group t by m into l
select new DatabaseObject()
{
Description = string.Format("{0}/{1}", l.Key.month, l.Key.year),
Value = l.Sum(v => v.Value), //Sum(v => v.Value),
Category = "Grouped",
DateOccurred = l.Max(v => v.DateOccurred)
}).AsQueryable();
I have fixed this by declaring an list of type IEnumerable and using ToList() to cast the database interaction, finally the query is then recast AsQueryable()