linq group by multipe aggregates - sql

Question

Im new to Linq and Im sure that I have gone about this in a convoluted manner. Im trying to do something like this SQL in Linq:
SELECT DISTINCT
count(vendor) as vendorCount,
reqDate,
status,
openDate,
item,
poDate,
count(responseDate) as responseCount
FROM
myTable
GROUP BY
reqDate, status, openDate, item, poDate
HAVING
reqDate > openDate
Here is what I have so far.
var groupQuery = (from table in dt.AsEnumerable()
group table by new
{
vendor = table["vendor"], reqdate = table.Field<DateTime>("ReqDate"), status = table["status"],
open = table["openDate"],
item = table["item"),
podate = table.Field<DateTime>("PODate"), responsedate = table.Field<DateTime>("responseDate"),
}
into groupedTable
where Having(groupedTable.Key.reqdate, groupedTable.Key.openDate) == 1
select new
{
x = groupedTable.Key,
y = groupedTable.Count()
}).Distinct();
foreach (var req in groupQuery)
{
Console.WriteLine("cols: {0} count: {1} ",
req.x, req.y);
}
The Having() is a function that takes two datetime parameters and returns a 1 if the reqDate is greater than the openDate. It compiles and runs, but it obviously does not give me the results I want. Is this possible using Linq? I want to push this data to an excel spreadsheet so Im hoping to create a datatable from this linq query. Would I be better off just creating a dataview from my datatable and not mess with Linq?

Answer 1

The SQL code is grouping by only some of the fields, while your LINQ statement is grouping by all of the fields, so the only items that would get grouped would be duplicates. If you group by only the fields that the SQL query groups by, you should get the correct answer. Your Having() method words fine, but is not necessary and is less readable.
var groupQuery = (from table in dt.AsEnumerable()
group table by new
{
reqdate = table.Field<DateTime>("ReqDate"),
status = table["status"],
open = table["openDate"],
item = table["item"),
podate = table.Field<DateTime>("PODate")
}
into groupedTable
where groupedTable.Key.reqdate > groupedTable.Key.openDate
select new
{
x = groupedTable.Key,
VenderCount = groupedTable.Select(t => t["vendor"])
.Distinct()
.Count(),
ResponseCount = groupedTable.Select(t => t.Field<DateTime>("responseDate"))
.Distinct()
.Count()
}).Distinct();