I have the following grouping statement:
var test = from a in MyDC.Table
where .....
group a by a.Date into daygroups
select new MyModel()
{
TheCount = (from c in daygroups
where c.AppointDate < "the date of the daygroups for this day").Sum( d =>d)
}
Basically, the query looks in a table for appointments within a certain month and does counts by day for each day of the month. Daygroups groups the results by days so I can do the daily counts. How do I specify the date within the daygroups?
Thanks.
Try
where c.AppointDate < daygroups.Key
Your date is in daygroups.Key
When grouping with LINQ, the value you are grouping on ends up in the Key property of the IGrouping object, daygroups in your case.
Something like this, perhaps:
var test = from a in MyDC.Table
where .....
group a by a.Date into daygroups
select new MyModel {
TheCount = daygroups.Where(d => d.AppointDate < daygroups.Key).Count()
}
Related
I have data from which I should count rows by weeks and weekdays. As result I should get
Starting day of the week, weekday, count of data for that day
I have tried this code:
var GroupedByDate = from r in dsDta.Tables[0].Rows.Cast<DataRow>()
let eventTime = (DateTime)r["EntryTime"]
group r by new
{
WeekStart = DateTime(eventTime.Year, eventTime.Month, eventTime.AddDays(-(int)eventTime.DayOfWeek).Day),
WeekDay = eventTime.DayOfWeek
}
into g
select new
{
g.Key,
g.WeekStart,
g.WeekDay,
LoadCount = g.Count()
};
However, from DateTime(eventTime.Year, ...)
I get an error "C# non-invocable member datetime cannot be used like a method."
What to do differently?
The immediate error is due to you missing the new part from your constructor call. However, even with that, you'd still have a problem as you're using the month and year of the existing date, even if the start of the week is in a previous month or year.
Fortunately, you can simplify it very easily:
group r by new
{
WeekStart = eventTime.AddDays(-(int)eventTime.DayOfWeek)),
WeekDay = eventTime.DayOfWeek
}
Or if eventTime isn't always a date, use eventTime.Date.AddDays(...).
Alternatively, for clarity, you could extract a separate method:
group r by new
{
WeekStart = GetStartOfWeek(eventTime)
WeekDay = eventTime.DayOfWeek
}
...
private static DateTime GetStartOfWeek(DateTime date)
{
// Whatever implementation you want
}
That way you can test the implementation of GetStartOfWeek separately, and also make it more complicated if you need to without it impacting your query.
I have a table the contains appointments. These appointments have different statuses (byte from 1 to 5) and dates; the column for the date is simply called AppointDate. I pass in a list of IDs and I want to group the result based on the status AND whether the date of the appointment is past or not.
TheIDs is a list of longs that's passed in as the parameter. This is what I have so far:
var TheCounterInDB = (from a in MyDC.Appointments
where TheIDs.Contains(a.ID)
group a by a.AppointStatus into TheGroups
select new {
TheStatus = TheGroups.Key,
TheTotalCount = TheGroups.Count(),
TheLateCount = ?,
ThePendingCount = ?
}).ToList();
Basically, I want TheLateCount to be the count of all the appointments where status is 1 AND the date is past and ThePendingCount to be the count where status is 1 AND the date is not past. My anonymous type is good to return the count of all the different statuses (that's where the .Key is) but I'm wondering how to best add the date requirement into the grouping.
Thanks for your suggestions.
var TheCounterInDB = (from a in MyDC.Appointments
where TheIDs.Contains(a.ID)
group a by a.AppointStatus into TheGroups
select new {
TheStatus = TheGroups.Key,
TheTotalCount = TheGroups.Count(),
TheLateCount = TheGroups.Count(x => x.AppointStatus == 1 && x.AppointDate < DateTime.Today),
ThePendingCount = TheGroups.Count(x => x.AppointStatus == 1 && x.AppointDate >= DateTime.Today)
}).ToList();
i have some problems with my c# code everywhere in the Examples they do it like me but somehow i gonna get some errors
Compiler says at g.Datum he doesn' t know Datum
and at "return query" he says - cannot convert, there is a explicit convert
var query = (from p in dataContext.Untersuchungen
orderby p.Datum
group p by p.Datum into g
let number = (from n in dataContext.Untersuchungen
where n.Datum == g.Datum
select n).Count()
select new StatsistikObjekt() { Date1 = g.Datum, number1 = number });
return query;
hope you can help me =)
The type of the range variable g is the group, which indeed doesn't have a Datum value.
You can fix that bit easily, given your grouping (which uses Datum as the key)- and make your query simpler too by just counting the size of the group:
var query = (from p in dataContext.Untersuchungen
orderby p.Datum
group p by p.Datum into g
select new StatsistikObjekt() { Date1 = g.Key,
number1 = g.Count() });
As for the return value - we can't really help you on that one, as we don't know the return type you're trying to return.
Try
g.Key instead of g.Datum
I have a Linq query that basically counts how many entries were created on a particular day, which is done by grouping by year, month, day. The problem is that because some days won't have any entries I need to back fill those missing "calendar days" with an entry of 0 count.
My guess is that this can probably be done with a Union or something, or maybe even some simple for loop to process the records after the query.
Here is the query:
from l in context.LoginToken
where l.CreatedOn >= start && l.CreatedOn <= finish
group l by
new{l.CreatedOn.Year, l.CreatedOn.Month, l.CreatedOn.Day} into groups
orderby groups.Key.Year , groups.Key.Month , groups.Key.Day
select new StatsDateWithCount {
Count = groups.Count(),
Year = groups.Key.Year,
Month = groups.Key.Month,
Day = groups.Key.Day
}));
If I have data for 12/1 - 12/4/2009 like (simplified):
12/1/2009 20
12/2/2009 15
12/4/2009 16
I want an entry with 12/3/2009 0 added by code.
I know that in general this should be done in the DB using a denormalized table that you either populate with data or join to a calendar table, but my question is how would I accomplish this in code?
Can it be done in Linq? Should it be done in Linq?
I just did this today. I gathered the complete data from the database and then generated a "sample empty" table. Finally, I did an outer join of the empty table with the real data and used the DefaultIfEmpty() construct to deal with knowing when a row was missing from the database to fill it in with defaults.
Here's my code:
int days = 30;
// Gather the data we have in the database, which will be incomplete for the graph (i.e. missing dates/subsystems).
var dataQuery =
from tr in SourceDataTable
where (DateTime.UtcNow - tr.CreatedTime).Days < 30
group tr by new { tr.CreatedTime.Date, tr.Subsystem } into g
orderby g.Key.Date ascending, g.Key.SubSystem ascending
select new MyResults()
{
Date = g.Key.Date,
SubSystem = g.Key.SubSystem,
Count = g.Count()
};
// Generate the list of subsystems we want.
var subsystems = new[] { SubSystem.Foo, SubSystem.Bar }.AsQueryable();
// Generate the list of Dates we want.
var datetimes = new List<DateTime>();
for (int i = 0; i < days; i++)
{
datetimes.Add(DateTime.UtcNow.AddDays(-i).Date);
}
// Generate the empty table, which is the shape of the output we want but without counts.
var emptyTableQuery =
from dt in datetimes
from subsys in subsystems
select new MyResults()
{
Date = dt.Date,
SubSystem = subsys,
Count = 0
};
// Perform an outer join of the empty table with the real data and use the magic DefaultIfEmpty
// to handle the "there's no data from the database case".
var finalQuery =
from e in emptyTableQuery
join realData in dataQuery on
new { e.Date, e.SubSystem } equals
new { realData.Date, realData.SubSystem } into g
from realDataJoin in g.DefaultIfEmpty()
select new MyResults()
{
Date = e.Date,
SubSystem = e.SubSystem,
Count = realDataJoin == null ? 0 : realDataJoin.Count
};
return finalQuery.OrderBy(x => x.Date).AsEnumerable();
I made a helper function which is designed to be used with anonymous types, and reused in as generic way as possible.
Let's say this is your query to get a list of orders for each date.
var orders = db.Orders
.GroupBy(o => o.OrderDate)
.Select(o => new
{
OrderDate = o.Key,
OrderCount = o.Count(),
Sales = o.Sum(i => i.SubTotal)
}
.OrderBy(o => o.OrderDate);
For my function to work please note this list must be ordered by date. If we had a day with no sales there would be a hole in the list.
Now for the function that will fill in the blanks with a default value (instance of anonymous type).
private static IEnumerable<T> FillInEmptyDates<T>(IEnumerable<DateTime> allDates, IEnumerable<T> sourceData, Func<T, DateTime> dateSelector, Func<DateTime, T> defaultItemFactory)
{
// iterate through the source collection
var iterator = sourceData.GetEnumerator();
iterator.MoveNext();
// for each date in the desired list
foreach (var desiredDate in allDates)
{
// check if the current item exists and is the 'desired' date
if (iterator.Current != null &&
dateSelector(iterator.Current) == desiredDate)
{
// if so then return it and move to the next item
yield return iterator.Current;
iterator.MoveNext();
// if source data is now exhausted then continue
if (iterator.Current == null)
{
continue;
}
// ensure next item is not a duplicate
if (dateSelector(iterator.Current) == desiredDate)
{
throw new Exception("More than one item found in source collection with date " + desiredDate);
}
}
else
{
// if the current 'desired' item doesn't exist then
// create a dummy item using the provided factory
yield return defaultItemFactory(desiredDate);
}
}
}
The usage is as follows:
// first you must determine your desired list of dates which must be in order
// determine this however you want
var desiredDates = ....;
// fill in any holes
var ordersByDate = FillInEmptyDates(desiredDates,
// Source list (with holes)
orders,
// How do we get a date from an order
(order) => order.OrderDate,
// How do we create an 'empty' item
(date) => new
{
OrderDate = date,
OrderCount = 0,
Sales = 0
});
Must make sure there are no duplicates in the desired dates list
Both desiredDates and sourceData must be in order
Because the method is generic if you are using an anonymous type then the compiler will automatically tell you if your 'default' item is not the same 'shape' as a regular item.
Right now I include a check for duplicate items in sourceData but there is no such check in desiredDates
If you want to ensure the lists are ordered by date you will need to add extra code
Essentially what I ended up doing here is creating a list of the same type with all the dates in the range and 0 value for the count. Then union the results from my original query with this list. The major hurdle was simply creating a custom IEqualityComparer. For more details here: click here
You can generate the list of dates starting from "start" and ending at "finish", a then step by step check the number of count for each date separately
I'm having a hard time understanding how I can form a LINQ query to do the following:
I have a table CallLogs and I want to get back a single result which represents the call that has the longest duration.
The row looks like this:
[ID] [RemoteParty] [Duration]
There can be multiple rows for the same RemoteParty, each which represents a call of a particular duration. I'm wanting to know which RemoteParty has the longest total duration.
Using LINQ, I got this far:
var callStats = (from c in database.CallLogs
group c by c.RemoteParty into d
select new
{
RemoteParty = d.Key,
TotalDuration = d.Sum(x => x.Duration)
});
So now I have a grouped result with the total duration for each RemoteParty but I need the maximum single result.
[DistinctRemoteParty1] [Duration]
[DistinctRemoteParty2] [Duration]
[DistinctRemotePartyN] [Duration]
How can I modify the query to achieve this?
Order the result and return the first one.
var callStats = (from c in database.CallLogs
group c by c.RemoteParty into d
select new
{
RemoteParty = d.Key,
TotalDuration = d.Sum(x => x.Duration)
});
callStats = callStats.OrderByDescending( a => a.TotalDuration )
.FirstOrDefault();
Have a look at the "Max" extension method from linq
callStats.Max(g=>g.TotalDuration);