I have the next IQueryable which filter a Double value:
var pQuery =
(from c in db.TABLE
select new
{
cDate = c.DATE,
dMid = (double)c.MID,
})
.Where("dMid > 13.5");
When I see the IntelliTrace, Linq generate the next query:
select DATE, MID
from TABLE
where MID > cast(135 as float(53))
I don't why Linq delete decimal separator and convert the filter expression from 13.5 to 135.
Someone can help me???
Thanks!!!!
And the end it was easier than I thought. User lc. gives me the solution using "f" character
var pQuery =
(from c in db.TABLE
select new
{
cDate = c.DATE,
dMid = (double)c.MID,
})
.Where("dMid > 13.5f");
.. and this is translated to:
select DATE, MID
from TABLE
where MID > cast(13.5 as float(53))
Related
How we can write a LINQ query for following select sql query:
string brandid="1,2,3"
string bodystyleid="1,2,3"
-------------------
-----------------
select * from car
where brandid in (brandid)
and bodystyleid in (brandid)
----------------------
-------------------
My specific requirement is that if brandid or bodystyleid is blank(if user does not select
any checkbox of a particular search option) query should return all record for that particular where condition.
Please guide me.
Thanks,
Paul
In order to fulfil your requirement about returning all items if none are specified, you need to check for the lists being empty.
var brands = brandid.Split(',').Select(x => Int32.Parse(x));
var styles = bodystyleid.Split(',').Select(x => Int32.Parse(x));
var result = from c in car
where (!brands.Any() || brands.Contains(c.brandid))
&& (!styles.Any() || styles.Contains(c.bodystyleid))
select c;
(similar to sgmoore's solution, but includes the check for no brand/style specified)
I've not actually checked how this gets converted back to SQL - it may be more efficient to use a flag to indicate whether there are any values:
var brands = ....; // As above
bool anyBrands = brands.Any()
var result = from c in car
where (!anyBrands || brands.Contains(c.brandid))
.....
Is bodystyleid meant to check brandid or bodystyleid? (I am assuming bodystyleid, however have wrote the query to match the query in the question (brandid))
As a start you could do:
var results = (from c in car
where c.brandid.Contains(brandid)
&& c.bodystyleid.Contains(brandid)
select c).ToList();
var brandids = brandid .Split(',').Select(n => int.Parse(n)).ToList();
var bodyStyleids = bodystyleid.Split(',').Select(n => int.Parse(n)).ToList();
var results =
(from c in car where
brandids.Contains(c.brandid) &&
bodyStyleids.Contains(c.bodystyleid)
select c
).ToList();
the Ids you have are as strings with comma delimiter, you need them to be collections like List of the same type as your Ids of the Car table, so if brandid column is int then brandids has to be List<long>, then you can do
var results = (
from c in cars
where brandids.Contains(c.brandid) && bodystyleid.Contains(c.bodystyleid)
select c).ToList();
I am using BLToolKit in a project of mine and I was trying to get this to work. What I don't like is that I am trying to average a bunch of temps down to the minute, but the select statement that is being generated groups by the minute but then selects the original time. I think I am doing the linq expression correctly (but then again, i am not getting the results i expect). (this is C#, if you care) Anyone know what is going wrong?
var test = (from r in db.SensorReadingRaws
where r.TimeLogged < DateTime.Now.AddMinutes(-2)
group r by new
{
Sensor = r.SensorNumber,
//group time down to the minute
Time = r.TimeLogged.AddSeconds(-1 * r.TimeLogged.Second).AddMilliseconds(-1 * r.TimeLogged.Millisecond)
} into grouped
select new SensorReading
{
SensorNumber = grouped.Key.Sensor,
TimeLogged = grouped.Key.Time,
Reading = (int)grouped.Average(x => x.Reading)
}).ToList();
textBox1.Text = db.LastQuery;
and the resulting query is this
SELECT
[r].[SensorNumber],
[r].[TimeLogged],
Avg([r].[Reading]) as [c1]
FROM
[SensorReadingRaw] [r]
WHERE
[r].[TimeLogged] < #p1
GROUP BY
[r].[SensorNumber],
DateAdd(Millisecond, Convert(Float, -DatePart(Millisecond, [r].[TimeLogged])), DateAdd(Second, Convert(Float, -DatePart(Second, [r].[TimeLogged])), [r].[TimeLogged])),
[r].[TimeLogged]
I discovered that
BLToolkit.Data.Linq.Sql.AsSql<T>(T obj)
can be used as a workaround for this case.
When applying this function to the required grouped key properties in select statement you get rid of grouping/selecting an original field.
It may look something like:
_queryStore.Leads().
GroupBy(x => new {
x.LeadDate.Hour,
x.LeadDate.Minute
}).
Select(x => new {
Hour = Sql.AsSql(x.Key.Hour),
Minute = Sql.AsSql(x.Key.Minute),
Count = x.Count()
});
and in your particular case:
var test = (from r in db.SensorReadingRaws
where r.TimeLogged < DateTime.Now.AddMinutes(-2)
group r by new
{
Sensor = r.SensorNumber,
//group time down to the minute
Time = r.TimeLogged.AddSeconds(-1 * r.TimeLogged.Second).AddMilliseconds(-1 * r.TimeLogged.Millisecond)
} into grouped
select new SensorReading
{
SensorNumber = grouped.Key.Sensor,
TimeLogged = Sql.AsSql(grouped.Key.Time),
Reading = (int)grouped.Average(x => x.Reading)
}).ToList();
I got same issue yesterday.
Today I found a workaround. The idea is to write 2 linq queries. First transforming the data and the second grouping the result:
var bandAndDate =
(from r in repo.Entities
select new {Band = r.Score / 33, r.StartTime.Date});
var examsByBandAndDay =
(from r in bandAndDate
group r by new {r.Band, r.Date } into g
select new { g.Key.Date, g.Key.Band, Count = g.Count() }).ToList();
Both this queries run one SQL that do the job:
SELECT
[t1].[c1] as [c11],
[t1].[c2] as [c21],
Count(*) as [c3]
FROM
(
SELECT
[r].[Score] / 33 as [c2],
Cast(Floor(Cast([r].[StartTime] as Float)) as DateTime) as [c1]
FROM
[Results] [r]
) [t1]
GROUP BY
[t1].[c2],
[t1].[c1]
I tried to use the suggestion provided here for using In operator in linq but, i am not able to convert my requirement into LINQ statement.
Below is the SQL query which i need to convert to Linq
select *
from navigator_user_field_property
where user_id = 'albert'
and field_id in (
select field_id
from navigator_entity_field_master
where entity_id = 1
and use_type = 0)
order by field_id
I want this to be converted to a Efficient Linq.
Most of the answers deal with the predetermined list of string array which is not working in my case.
Thanks
Looks like a join to me:
var query = from navigator in db.NavigatorUserFieldProperties
where navigator.UserId == "albert"
join field in db.NavigatorEntityFieldMasters
.Where(f => f.EntityId == 1 && f.UseType == 0)
on navigator.FieldId equals field.FieldId
select navigator;
Note that this will return the same value multiple times if there are multiple fields with the same ID - but I suspect that's not the case.
You could do a more literal translation like this:
var query = from navigator in db.NavigatorUserFieldProperties
where navigator.UserId == "albert" &&
db.NavigatorEntityFieldMasters
.Where(f => f.EntityId == 1 && f.UseType == 0)
.select(f => f.FieldId)
.Contains(navigator.FieldId)
select navigator;
... and that may end up translating to the same SQL... but I'd personally go with the join.
Here is an efficient and readable LINQ query:
var fields =
from field in db.navigator_entity_field_masters
where field.entity_id == 1 && field.user_type == 0
select field;
var properties =
from property in db.navigator_user_field_properties
where property.user_id == "albert"
where fields.Contains(property.field)
select property;
Look mama!! Without joins ;-)
I can't seem to find any good reference on this. I have a lot of data in SQL with dates. So I wanted to make a line chart to show this data over time. If I want to show it over a period of days then I need to group by days.. But the LOGDATE is the full date.. not the DAY..
So I have this below, but LINQ doesn't know what 'DayOfYear' property is...
var q = from x in dc.ApplicationLogs
let dt = x.LogDate
group x by new { dayofyear = dt.Value.DayOfYear } into g
select new
{
iCount = g.Count(),
strDate = g.Key
};
In EF core you can use DateTime.Date to get the date portion of a DateTime value.
In EF6 you can use DbFunctions.TruncateTime:
to return the given date with the time portion cleared
var q = from x in dc.ApplicationLogs
let dt = x.LogDate.Date
// EF6:let dt = DbFunctions.TruncateTime(x.LogDate)
group x by dt into g
select new
{
iCount = g.Count(),
strDate = g.Key
};
You want .Date to get the date part of a DateTime not DayOfyear unless you are deliberately trying to put the same day of the year from each year into the group.
Why are you using:
let dt = x.LogDate
group x by new { dayofyear = dt.Value.DayOfYear } into g
instead of just:
group x by x.LogDate.Value.DayOfYear into g
I'm not sure about this, but it's possible using an anonymous object like that in your group by clause is messing up L2S.
Here you go
let d = new DateTime(n.time.Year, n.time.Month, n.time.Day) group n by d into grp select grp
Let's ay I have this query:
var results = from row in db.Table select row;
How can I access this:
string name = results[0]["columnName"];
if you really want a particular index you can use the Skip() method with First().
var rowOffset = 0;
var results = (from row in db.Table
select row).Skip(rowOffset).First()["columnName"];
But unless you are using a Where clause I would really recommend using the indexer. The indexer is pretty much a direct reference while the LINQ statement would be using the objects iterator.
Also don't forget you can do much more advanced stuff with LINQ.
var rowOffset = 0;
var pageLength = 10;
var results = (from row in db.Table
let colValue = row["columnname"]
where colValue != null
select colValue.ToString()
).Skip(rowOffset)
.Take(pageLength)
.ToArray();
var commaString = string.Join(", ", results);
If you specifically just want the zeroth element, you can use results.First()
results is a IEnumerable list of Rows. So you can get it with a simple foreach.
foreach(var row in results)
{
string name = row["columnName"];
}
(from row in db.Table select row).First().columnName