Develop Reference

Recursive/Hierarchical Query in LINQ

Scenario is,
im using EntityFrame Work 6. I have a DB have table having structure below.
cat_id geo_id parent_id geo_name
Root 1 NULL Pakistan
Province 2 1 Punjab
District 3 2 Attock
City 4 3 Attock
City 5 3 Fateh Jang
City 6 3 Hasan Abdal
Table have hierarchical data in relational form,as you can see.
I want to traverse this hierarchy, want to specific parent level, If im at geo_id 6 then I want to go parent_id 3 and get value Attock or want to go to parent_id 2 and want to get value Punjab.
Moral of the story is,standing at any child,want traverse till specified parent or grand parent,not entire hierarchy. Below is code I have tried but it gives me only its immediate parent.
More Shortly, Want a LINQ query,which will return name of specified parent or grand parent,For Example. I can ask my query, "hey! im Hasan Abdal(City),tell me my Province"
Province = (from cp in db.geo_hierarchy
join mp in db.geo_hierarchy on cp.parent_id equals mp.geo_id
where cp.geo_name == risk.geo_hierarchy.geo_name
select mp.geo_name).FirstOrDefault()
see full code below,it used in inside LINQ query's select clause
Risklists = (from risk in db.risk_cat_detail
where risk.occurance_date.Value.Year==2014 && risk.occurance_date.Value.Month>=6 && risk.occurance_date.Value.Month<=9
select new risk_cat_detail_contract()
{
cat_id = risk.cat_id,
catdesc = risk.category_main.cat_name,
risk_cat_detail_id = risk.risk_cat_detail_id,
trans_date = risk.trans_date.Value,
occurance_date = risk.occurance_date.Value,
occurance_time = risk.occurance_time,
geo_id = risk.geo_id,
geo_desc = risk.geo_hierarchy.geo_name,
Province = (from cp in db.geo_hierarchy
join mp in db.geo_hierarchy on cp.parent_id equals mp.geo_id
where cp.geo_name == risk.geo_hierarchy.geo_name
select mp.geo_name).FirstOrDefault()
}).ToList<risk_cat_detail_contract>();
Help me out,Thanks in Advance

Try this:
var geo_hierarchy = new []
{
new { cat_id = "Root", geo_id = 1, parent_id = (int?)null, geo_name = "Pakistan", },
new { cat_id = "Province", geo_id = 2, parent_id = (int?)1, geo_name = "Punjab", },
new { cat_id = "District", geo_id = 3, parent_id = (int?)2, geo_name = "Attock", },
new { cat_id = "City", geo_id = 4, parent_id = (int?)3, geo_name = "Attock", },
new { cat_id = "City", geo_id = 5, parent_id = (int?)3, geo_name = "Fateh Jang", },
new { cat_id = "City", geo_id = 6, parent_id = (int?)3, geo_name = "Hasan Abdal", },
};
var map = geo_hierarchy.ToDictionary(x => x.geo_id);
Func<int, string, string> up = null;
up = (geo_id, cat_id) =>
{
var record = map[geo_id];
return
record.cat_id == cat_id
? record.geo_name
: (record.parent_id.HasValue
? up(record.parent_id.Value, cat_id)
: null);
};
var result = up(5, "Province"); // -> "Punjab"

Joint 3 tables in linq and return value of nested table with max id

I have there tables as you can see :
line:
id Linename
1 line1
2 line2
3 line3
joint:
id lineId jointname
1 1 joint1
2 2 joint2
3 1 joint3
fitup:
id jointid fitupdate state
1 1 2012/12/12 acc
2 1 2013/12/12 rej
3 2 2015/12/12 acc
4 2 2016/12/12 rej
Result i need:
id Linename jointname fitupdate state
1 line1 joint1 2013/12/12 rej
2 line2 joint2 2016/12/12 rej
The fitup table has a state I need the final state based on max id.
In the fitup table i have multi rows for each joint but i need the date(string) of max id in the result query .
Here is my query:
var q = from j in _ctx.Joints
join l in _ctx.Lines on j.LineId equals l.Id
join spo in _ctx.Spools on j.SpoolId equals spo.Id
join sup in _ctx.Supports on j.SupportId equals sup.Id
join shee in _ctx.Sheets on j.SheetId equals shee.Id
join Fit in _ctx.FitUpDetails on j.Id equals Fit.JointId into g2
from y2 in g2.DefaultIfEmpty()
join weld in _ctx.WeldDetails on j.Id equals weld.JointId into g
from y1 in g.DefaultIfEmpty()
join end in _ctx.Ends on j.EndId equals end.Id
join basemat in _ctx.BaseMaterials on j.BaseMaterialId equals basemat.Id
join TestPack in _ctx.TestPackages on j.TestPackageId equals TestPack.Id
group new { j, l,y2,y1} by new { shee, j, l, spo, sup, y2, y1, end, basemat, TestPack } into grouping
let maxFitById = grouping.Select(item => item.y2)
.Where(item => item != null)
.OrderByDescending(item => item.Id)
let maxweldById = grouping.Select(item => item.y1)
.Where(item => item != null)
.OrderByDescending(item => item.Id)
select new ViewFront()
{
Id = grouping.Key.j.Id,
LineId = grouping.Key.l.LineNumber,
SubmitDateTime = grouping.Key.j.SubmitDateTime,
JointNumber = grouping.Key.j.JointNumber,
BaseMaterialId = grouping.Key.basemat.Name,
FitUpAccept = maxFitById.FirstOrDefault().StateStep1,
FitUpAcceptMain = maxFitById.FirstOrDefault().StateStep2,
JointClass = grouping.Key.j.JointClass,
End = grouping.Key.end.Name,
JointSize = grouping.Key.j.JointSize,
LeftMaterialItemCode = grouping.Key.j.LeftMaterialItemCode,
LeftMaterialLength = grouping.Key.j.LeftMaterialLength.ToString(),
MagneticTest = grouping.Key.j.MagneticTest,
PenetrationTest = grouping.Key.j.PenetrationTest,
PostWeldHeatTreatment = grouping.Key.j.PostWeldHeatTreatment,
RemarkState = grouping.Key.j.RemarkState,
RightMaterialItemCode = grouping.Key.j.RightMaterialItemCode,
RightMaterialLength = grouping.Key.j.RightMaterialLength.ToString(),
RadiographyTest = grouping.Key.j.RadiographyTest,
SheetId = grouping.Key.shee.SheetNumber,
ShopField = grouping.Key.j.ShopField,
SpoolId = grouping.Key.spo.SpoolNumber,
SupportId = grouping.Key.sup.SupportNumber,
TestPackageId = grouping.Key.TestPack.PackageNumber,
THK = grouping.Key.j.THK,
UltrasonicTest = grouping.Key.j.UltrasonicTest,
WeldAccept = maxweldById.FirstOrDefault().StateStep1,
WeldAcceptMain = maxweldById.FirstOrDefault().StateStep2
};
In this query FitUpAccept is the state .
Joint table data
weld :
fitup:
result:

The following code does what you need. Now some explanations:
I kept only the tables relevant for the described output data just to keep it simpler.
When grouping by - If you select the entire objects as you did then you will always get "groups" of a single record - I group the wanted data just by the key - In this case the non aggregated fields. Make sure that you are not grouping by the same fields that you want to actually do aggregation operations by them ( like y2 )
Because it is a left join to the FitUpDetails I must make sure that I remove all the null records and whenever I access a property of that object to make sure it is not null - c# 6.0 syntax of ?..
Now for the By max id part - if I put it into words: "Grouping the data by X, and then for each group ordering it by Y, take first record -> its properties"
So to the code:
var result = (from j in Joints
join l in Lines on j.LineId equals l.Id
join f in FitUpDetails on j.Id equals f.JointId into g2
from y2 in g2.DefaultIfEmpty()
group new { j, l, y2 } by new { j.Id, l.LineName, j.JointName } into grouping
let maxFitById = grouping.Select(item => item.y2)
.Where(item => item != null)
.OrderByDescending(item => item.Id)
.FirstOrDefault()
select new
{
Id = grouping.Key.Id,
LineName = grouping.Key.LineName,
JointName = grouping.Key.JointName,
FitUpdate = maxFitById?.FitUpdate,
State = maxFitById?.State
}).ToList();
Used this for testing it:
List<dynamic> Joints = new List<dynamic>
{
new { Id = 1, LineId = 1, JointName = "joint1" },
new { Id = 2, LineId = 2, JointName = "joint2" },
new { Id = 3, LineId = 1, JointName = "joint3" },
};
List<dynamic> Lines = new List<dynamic>
{
new { Id = 1, LineName = "line1" },
new { Id = 2, LineName = "line2" },
new { Id = 3, LineName = "line3" },
};
List<dynamic> FitUpDetails = new List<dynamic>
{
new { Id = 1, JointId = 1, FitUpdate = new DateTime(2012,12,12), State = "acc" },
new { Id = 2, JointId = 1, FitUpdate = new DateTime(2013,12,12), State = "rej" },
new { Id = 1, JointId = 2, FitUpdate = new DateTime(2015,12,12), State = "acc" },
new { Id = 4, JointId = 2, FitUpdate = new DateTime(2016,12,12), State = "rej" },
};

Grouping troubles in LINQ

I have some list of structures like this:
struct va_data
{
public int item_id;
public int type_id;
public double item_value;
public DateTime value_date;
}
I trying group the list by type_id and take items where value_date is maximum then group by item_id and take items only where item_value is minimum
There is my syntax
from x in dataList
group x by x.type_id into grouped
select grouped.Where(x => x.value_date == grouped.Max(y => y.value_date))
.GroupBy(x => x.item_id) // and here i was stuck.
Example
var dataList = new []
{
new va_data {item_id = 1, type_id = 1, item_value = 0, value_date = "2013.07.29"},
new va_data {item_id = 1, type_id = 1, item_value = 1, value_date = "2013.07.30"},
new va_data {item_id = 2, type_id = 1, item_value = 0, value_date = "2013.07.29"},
new va_data {item_id = 2, type_id = 1, item_value = 1, value_date = "2013.07.29"},
new va_data {item_id = 4, type_id = 2, item_value = 5, value_date = "2013.07.29"},
new va_data {item_id = 4, type_id = 3, item_value = 9, value_date = "2013.07.30"},
};
The result must be
var dataListResult = new []
{
new va_data {item_id = 1, type_id = 1, item_value = 1, value_date = "2013.07.30"},
new va_data {item_id = 2, type_id = 1, item_value = 0, value_date = "2013.07.29"},
new va_data {item_id = 4, type_id = 2, item_value = 5, value_date = "2013.07.29"},
}

Given the following class
class va_data
{
public int item_id;
public int type_id;
public double item_value;
public DateTime value_date;
}
and your example data, you can use a query like this:
from data in dataList
group data by new {data.item_id, data.type_id} into g
let max_value_date = g.Max(x => x.value_date)
from i in g.Where(x => x.value_date == max_value_date)
group i by i.item_id into g2
let min_item_value = g2.Min(x => x.item_value)
from x in g2
where x.item_value == min_item_value
select x;
to get the following result:

Just split your query into two parts - getting latest of each type, and then getting minimal of each item:
var latestOfEachType =
from d in dataList
group d by d.type_id into typeGroup
select typeGroup.OrderByDescending(x => x.value_date).First();
var result = from d in latestOfEachType
group d by d.item_id into itemGroup
select itemGroup.OrderBy(x => x.item_value).First();
This query will be executed as single query. But in this case it looks much more readable to me. Also don't use mutable structs!. Use classes instead.
EDIT: Thus you have several items for max date, then query needs two small tweaks - select all items where date is max, and use SelectMany to iterate over them:
var latestOfEachType =
from d in dataList
group d by d.type_id into typeGroup
let maxDate = typeGroup.Max(x => x.value_date)
select typeGroup.Where(x => x.value_date == maxDate);
var result = from d in latestOfEachType.SelectMany(g => g)
group d by d.item_id into itemGroup
select itemGroup.OrderBy(x => x.item_value).First();

Use the Linq Count

I want to show OrderDetails Count near the orders information in the grid but in the select Unit i can only select the Key and Count. What is the way to select the orders information?
var Q = from Data in Context.Orders
join D2 in Context.OrderDetails on Data.OrderID equals D2.OrderID
group Data by Data.OrderID into grouped
select new
{
grouped=g.Key,
Count = grouped.Count()
};

You can group it by whole order entity like
var Q = from Data in Context.Orders
join D2 in Context.OrderDetails on Data.OrderID equals D2.OrderID
group Data by Data into grouped
select new
{
OrderId = grouped.Key.OrderId,
OrderDate = grouped.Key.OrderDate
Shipping = grouped.Key.Shipping
.
.
.
Count = grouped.Count()
};
EDIT Linqpad program for similar query on in memory collection of objects
void Main()
{
var orders = new List<Order>{
new Order{OrderId = 1, DeliverIn = 5},
new Order{OrderId = 2, DeliverIn = 6},
new Order{OrderId = 3, DeliverIn = 5},
};
var lines = new List<OrderLine>{
new OrderLine{LineId = 1, OrderId = 1, ProductId = 1},
new OrderLine{LineId = 2, OrderId = 1, ProductId = 2},
new OrderLine{LineId = 3, OrderId = 1, ProductId = 3},
new OrderLine{LineId = 4, OrderId = 2, ProductId = 1},
new OrderLine{LineId = 5, OrderId = 2, ProductId = 3},
new OrderLine{LineId = 6, OrderId = 2, ProductId = 4},
};
var query = from o in orders join l in lines on
o.OrderId equals l.OrderId
group o by o into grouped
select new
{
Count = grouped.Count(),
grouped.Key.OrderId,
grouped.Key.DeliverIn
};
Console.WriteLine(query);
}
// Define other methods and classes here
public class Order
{
public int OrderId{get;set;}
public int DeliverIn{get;set;}
}
public class OrderLine
{
public int LineId{get;set;}
public int OrderId{get;set;}
public int ProductId{get;set;}
}
and if you don't have linq pad simply go and grab it from their site. It is simply awesome.

Check out IGrouping documentation on MSDN.
public interface IGrouping<out TKey, out TElement> : IEnumerable<TElement>,
IEnumerable
Pay attention to IEnumerable. Count is just an extension method of IEnumerable. You can easily Select from grouping or loop through it.
For example:
var Q = from Data in Context.Orders
join D2 in Context.OrderDetails on Data.OrderID equals D2.OrderID
group Data by Data.OrderID into grouped
select new
{
grouped=g.Key,
Count = grouped.Count(),
Orders = grouped.ToArray()
//you can also just return grouped itself to support lazy queries
};

Just flatten them into array or list and then get its count.
select new
{
Key = g.Key,
Orders = grouped.ToArray()
};
Then get count:
int count = result.Orders.Count; // Property of an array.

LINQ to SQL group by with take

I have a table that looks like this:
Id GroupId Value
and it has about 100 rows
How can I return the top 10 rows for value but with no duplicating GroupId?

This should do it:
var results = table
.GroupBy(x => x.GroupId)
.Select(x => new { Row = x, Value = x.Max(y => y.Value) })
.OrderByDescending(x => x.Value)
.Select(x => x.Row)
.Take(10);
Edit: Modified to return the entire object.

Not sure if this translates to LINQ-to-SQL, but here's an idea from L2Obj
var query = (from foo in foos
group foo by foo.GroupId into fg
select fg.OrderByDescending(f => f.Value).First())
.OrderByDescending(f => f.Value)
.Take(10);
In english, it groups on the GroupId and then selects the Foo with the highest Value from each group, orders those, and then takes 10. If anything, you could get a concrete list of your objects from L2SQL and then perform the grouping in memory, should not be a performance/memory issue since you say there are only 100 rows.
For LINQ-to-SQL, you might try something like this
var sqlQuery = (from foo in foos
join y in
(from f2 in foos
join x in
(from f1 in foos
group f1 by f1.GroupId into vg
select new { GroupId = vg.Key, MaxVal = vg.Max(f => f.Value) })
on f2.GroupId equals x.GroupId
where f2.Value == x.MaxVal
group f2 by f2.GroupId into mg
select new { GroupId = mg.Key, MinId = mg.Min(f => f.Id) })
on foo.Id equals y.MinId
orderby foo.Value descending
select foo).Take(10);
This is based on a SQL query to perform the same operation
Select top 10 f.*
From Foos f
Inner Join
(Select f.GroupID, min(f.Id) as MinId
From Foos f
Inner Join
(Select GroupId, Max(Value) as MaxVal
From Foos
Group By GroupId) x
on f.GroupId = x.GroupId
and f.Value = x.MaxVal
Group By f.GroupId) y
on f.Id = y.MinId
order by f.Value desc
It basically performs two groupings. The first gets the max value for each group, the second gets the min ID for each record from each group that has the max value (in case 2 records in a group have the same value), and then selects the top 10 records.

This one will get the full row values (it's working for me with the sample data I show bellow):
static void Main(string[] args)
{
Whatever one = new Whatever() {GroupId = 1, Id = 1, Value = 2};
Whatever two = new Whatever() { GroupId = 1, Id = 2, Value = 8 };
Whatever three = new Whatever() { GroupId = 2, Id = 3, Value = 16 };
Whatever four = new Whatever() { GroupId = 2, Id = 4, Value = 7 };
Whatever five = new Whatever() { GroupId = 3, Id = 5, Value = 21 };
Whatever six = new Whatever() { GroupId = 3, Id = 6, Value = 12 };
Whatever seven = new Whatever() { GroupId = 4, Id = 7, Value = 5 };
Whatever eight = new Whatever() { GroupId = 5, Id = 8, Value = 17 };
Whatever nine = new Whatever() { GroupId = 6, Id = 9, Value = 13 };
Whatever ten = new Whatever() { GroupId = 7, Id = 10, Value = 44 };
List<Whatever> list = new List<Whatever>();
list.Add(one);
list.Add(two);
list.Add(three);
list.Add(four);
list.Add(five);
list.Add(six);
list.Add(seven);
list.Add(eight);
list.Add(nine);
list.Add(ten);
var results = (from w in list
group w by w.GroupId into g
select new { GroupId = g.Key,
Value = g.Max(w => w.Value),
Id = g.OrderBy(w=>w.Value).Last().Id }).
OrderByDescending(w=>w.Value).Take(5);
foreach (var r in results)
{
Console.WriteLine("GroupId = {0},
Id = {1},
Value = {2}",
r.GroupId, r.Id, r.Value);
}
}
Output:
GroupId = 7, Id = 10, Value = 44
GroupId = 3, Id = 5, Value = 21
GroupId = 5, Id = 8, Value = 17
GroupId = 2, Id = 3, Value = 16
GroupId = 6, Id = 9, Value = 13