string[] names = { "Burke", "Connor", "Frank",
"Albert", "George", "Harris", "David" };
peoples[] people = {
new peoples("Connor",20),
new peoples("John",22),
new peoples("Merry",33),
new peoples("Frank",65),
new peoples("Frank",34),
new peoples("George",19)
};
var query = from n in names
join p in people on n equals p.Name into matching
select new { Name = n, Count = matching.Count() };
Please tell me dot notation of this query.
Thanks.
The dot notation for a join depends on what follows it and whether or not you've got an "into" clause (for a group join). In this case it would be:
var query = names.GroupJoin(people, n => n, p => p.Name,
(n, matching) => new { Name = n, Count = matching.Count() });
If you didn't use "into" it would use Join instead of GroupJoin
If you had anything other than just "select" afterwards, it would introduce a new transparent identifier to keep "(n, matching)" as a tuple, effectively.
Related
I'm trying to convert my SQL statement to a Linq statement and I'm not sure how to add the second COUNT to it. This is my SQL statement
SELECT l.Campus_Name, Labs = COUNT(*), LabsWithSubnets = COUNT(s.Lab_Space_Id)
FROM vw_Lab_Space l
LEFT JOIN vw_Subnet s on l.Lab_Space_Id = s.Lab_Space_Id
GROUP BY l.Campus_Name
ORDER BY 1
and this is my LINQ statement so far:
from l in Vw_Lab_Space
from s in Vw_Subnet
.Where(s => s.Lab_Space_Id == l.Lab_Space_Id)
.DefaultIfEmpty() // <=- triggers the LEFT JOIN
group l by new { l.Campus_Name } into g
orderby g.Key.Campus_Name
select new {
Campus_Name = g.Key.Campus_Name,
Labs = g.Count()
}
So I have everything but the LabsWithSubnets part in there. I'm just not sure how to add that in as I can't just do an s.Lab_Space_id.Count() in the select statement.
If you need table structure and sample data please see Need help creating an OUTER JOIN to count spaces.
Using your query as a basis, you need the groups to include s so you can count when non-null (I also removed the unnecessary anonymous object around the grouping key):
from l in Vw_Lab_Space
from s in Vw_Subnet
.Where(s => s.Lab_Space_Id == l.Lab_Space_Id)
.DefaultIfEmpty() // <=- triggers the LEFT JOIN
group new { l, s } by l.Campus_Name into g
orderby g.Key
select new {
Campus_Name = g.Key,
Labs = g.Count(),
LabsWithSubnets = g.Count(ls => ls.s != null)
}
However, rather than translate the SQL, I would probably take advantage of LINQ's group join to handle the query slightly differently:
var ans = from l in Vw_Lab_Space
join s in Vw_Subnet on l.Lab_Space_Id equals s.Lab_Space_Id into sj
group new { l, sj } by ls.Campus_Name into lsjg
select new {
Campus_Name = lsjg.Key,
NumLabs = lsjg.Count(),
LabsWithSubnets = lsjg.Sum(lsj => lsj.sj.Count())
};
PS Even in your query, I would use join...from...DefaultIfEmpty rather than from...from...where but depending on your database engine, may not matter.
I need to show list of authors group by last name first letter.
e.g.
A
Kim, Ami
Dim, Amaiar
jin, Amairaz
B
Bin, Bom
Kin, Bomo
C
Cin, Ci
Con, Co
....
Could some one please help me what's the best way to solve the above problem?
If you want to group by, use GroupBy, I assumed you want the output to be ordered (OrderBy), Change the GroupBy expression to match your exact requirment:
List<String> names = new List<String>{"Bill", "Mark", "Steve", "Amnon", "Benny"};
foreach(var g in names.GroupBy(name => name.First()).OrderBy(g => g.Key)){
Console.WriteLine(g.Key);
g.OrderBy(name => name).ToList().ForEach(Console.WriteLine);
}
Will output:
A
Amnon
B
Bill
Benny
M
Mark
S
Steve
You can use GroupBy extension method over Linq object to get the desire result.
List<string> firstNames = new List<string>(){ "Ami", "Amaiar","Amiraz","Bom","Bomo","Ci","Co" };
var groups = firstNames.GroupBy(x=>x[0]);
foreach (var element in groups)
{
Console.WriteLine("{0}", element.Key);
foreach (var word in element)
Console.WriteLine(" {0}", word);
}
I have a newbie LINQ question. I need to create two objects of same type from a list of strings. I need to append a text 'Direct' & "Indirect' to the string and use them as ID to create the two unique objects.
var vStrings = new List { "Milk", "Eggs", "Cheese" };
var vProducts = (from s in vStrings
select new Product { ID = s + "-Direct" })
.Union(
from s in vStrings
select new Product { ID = s + "-InDirect" });
You can see in the example above, I am using a Union to create two different objects, Is there a better way to rewrite this LINQ query?
Thanks for your suggestions
If you ever needed more suffixes, this might be a better way:
var strings = new List<string> { "Milk", "Eggs", "Cheese" };
var suffixes = new List<string> {"-Direct", "-InDirect"};
var products = strings
.SelectMany(_ => suffixes, (x, y) => new Product() {ID = x + y});
And it would only iterate over the original set of strings once.
This way isn't much shorter but I think it would be a little better such as there is only one Concat instead of many Union:
var vProducts2 = (from s in vStrings
select s + "-Direct").Concat(
from s in vStrings
select s + "-InDirect");
I have an array filled with long type values and for each value in the array I need to implement a query. I used foreach loop as you can see from the code below:
var result;
foreach(long id in PrdIdArr)
{
var mainQuery = (from o in db.OPERATIONs
join u in db.UNITs on o.OP_UNIT_ID equals u.UNIT_ID into smt
from s in smt
join x in db.XIDs on s.UNIT_ID equals x.UNIT_ID
where o.OP_OT_CODE == OtCode
where x.IDTYP_CD == "BSN"
where s.START_PRD_ID == id
where o.OP_UPD_DATE >= _StartDate
where o.OP_UPD_DATE <= _EndDate
select new
{
o.OP_ID,
o.OP_UPD_DATE,
x.EXTERNAL_ID,
o.OP_OS_CODE,
o.OP_START,
o.OP_ST_STATION,
s.START_PRD_ID
}).Take(_RowNumber);
//var result = mainQuery.ToList();
result.add(mainQuery.ToList());
}
data = this.Json(result);
data.JsonRequestBehavior = JsonRequestBehavior.AllowGet;
return data;
However, I have a problem in my code; I have to define a main list just before the foreach loop so that I could add results of each query to the that main list. my question is: How can I define this list as you can see at the beginning of my code? Thanks for the help...
How can I define this list as you can see at the beginning of my code?
Make
new {
o.OP_ID,
o.OP_UPD_DATE,
x.EXTERNAL_ID,
o.OP_OS_CODE,
o.OP_START,
o.OP_ST_STATION,
s.START_PRD_ID
}
into a concrete type (say QueryResult, although something a little more specific than that), and then just declare
var result = new List<QueryResult>();
Also, you should consider turning
foreach(long id in PrdIdArr)
and
where s.START_PRD_ID == id
into
where PrdIdArr.Contains(s.Start_PRD_ID)
var result = new List<object>();
foreach(long id in PrdIdArr)
{
....
result.Add(mainQuery.ToList());
}
You could do this:
var result = PrdIdArr.Select(id =>
from o in db.OPERATIONs
join u in db.UNITs on o.OP_UNIT_ID equals u.UNIT_ID into smt
from s in smt
join x in db.XIDs on s.UNIT_ID equals x.UNIT_ID
where o.OP_OT_CODE == OtCode
where x.IDTYP_CD == "BSN"
where s.START_PRD_ID == id
where o.OP_UPD_DATE >= _StartDate
where o.OP_UPD_DATE <= _EndDate
select new
{
o.OP_ID,
o.OP_UPD_DATE,
x.EXTERNAL_ID,
o.OP_OS_CODE,
o.OP_START,
o.OP_ST_STATION,
s.START_PRD_ID
}
.Take(_RowNumber)
.ToList()
).ToList();
I highly recommend performing some Extract Method refactorings, as the code is pretty complex and hard to understand/mange this way.
Just create the anonymous type outside with the same property names and the correct type
var result = Enumerable.Range(0, 0).Select(x => new
{
OP_ID = 1,
OP_UPD_DATE = DateTime.Now,
EXTERNAL_ID = 1,
OP_OS_CODE = 1,
OP_START = DateTIme.Now,
OP_ST_STATION = "",
START_PRD_ID = 1,
}).ToList();
And in your loop call AddRange
result.AddRange(mainQuery.ToList());
I have a LINQ statement I am trying to get right, so maybe going about this all wrong. My objective is to query a table and join in another table to get counts.
Places
ID, Display
ProfilePlaces
ID, PlaceID, Talk, Hear
Basically Places have ProfilePlaces in a one to many relationship. I want to get the number SUM of ProfilePlaces that have Talkand Hear. Talkand Hear are bit fields.
The following gives me a unique list of Places, so I need to add in the Talkand Hear counts.
var counts = from p in db.Places
join pp in db.ProfilePlaces on p.ID equals pp.PlaceID
group new { Place = p } by p.Display;
I thought something like this, but not having any luck
var counts = from p in db.Places
join pp in db.ProfilePlaces on p.ID equals pp.PlaceID
group new { Place = p,
Talk = pp.Count(t => t.Talk == true),
Hear = pp.Count(t => t.Hear == true)
} by p.Display;
Thanks for any help.
You want to do a GROUP JOIN to get the counts for each Place.
var counts2 = from p in places
join pp in profilePlaces on p.ID equals pp.PlaceID into g
select new
{
Place = p,
CountMeet = g.Count(a => a.Meet),
CountTalk = g.Count(a => a.Talk)
};
Here's the documentation on the different joins from MSDN:
http://msdn.microsoft.com/en-us/library/bb311040.aspx