Develop Reference

how to apply join or innerquery to connect two table

Here MyChildTable contains only id and the parent table contains id + name.
I have written a query to fetch the existing data from the table
await _dbContext.MyChildTable
.Where(c => c.CustomerId == **(select customerid from tableParent where customername= reqcustomername)**
Here i want to match customerId with the matching customer id from the second table ie tableParent.How to replace the query in to linq to get the proper record.select customerid from tableParent where customername= reqcustomername i want to replace this selection

I don't understand what you mean
so my maybe answer error
LINQ
using (entity entityData = new entity())
{
var checkqry2 = from T1 in entityData.MyChildTable.AsNoTracking()
join T2 in entityData.tableParent on
T1.CustomerId equals T2.customerid
where T1.customerid == "ID" && T2.customername == reqcustomername
group new { T2.customerid, T2.customername } by new { T1.customerid, T1.customername } into c
orderby c.Key.customerid
select new { customername=c.Key.customername,
customerid=c.Key.customerid,
};
}
you can try entity lambda
entity lambda
using (entity entityData = new entity())
{
var query1 = entityData.MyChildTable
.Join(entityData.tableParent , o => o.CustomerId , p => p.CustomerId , (o, p) => new
{
o.CustomerId,
p.customername,
}).Where(o => o.CustomerId == "123" && o.customername == "name").ToList();
}

Here I want to match customerId with the matching customer id from the
second table ie tableParent.How to replace the query in to linq to get
the proper record.select customerid from tableParent where
customername= reqcustomername i want to replace this selection
Well, lot of way around to handle this kind of scenario. Most easy and convenient way you could consider by using linq join or linq Enumerable which you can implement as following:
Sample Data:
var childList = new List<ChildTable>()
{
new ChildTable(){ Id =101,ChildName = "Child-A",CustomerId = 202},
new ChildTable(){ Id =102,ChildName = "Child-B",CustomerId = 203},
new ChildTable(){ Id =103,ChildName = "Child-C",CustomerId = 202},
new ChildTable(){ Id =104,ChildName = "Child-D",CustomerId = 204},
};
var parentList = new List<ParentTable>()
{
new ParentTable(){ Id =301,ParentName = "Parent-A",CustomerId = 202},
new ParentTable(){ Id =302,ParentName = "Parent-B",CustomerId = 202},
new ParentTable(){ Id =303,ParentName = "Parent-C",CustomerId = 203},
new ParentTable(){ Id =304,ParentName = "Parent-D",CustomerId = 205},
};
Linq Query:
Way One:
var findMatchedByCustId = from child in childList
where (from parent in parentList select parent.CustomerId)
.Contains(child.CustomerId)
select child;
Way Two:
var usingLinqJoin = (from parent in parentList
join child in childList on parent.CustomerId equals child.CustomerId
select parent).ToList().Distinct();
Output:
Note: If you need more information you could check our official document for Linq join and Linq Projction here.

GridView Only populating 1 result

I'm currently working to add Data to a GridView. The data comes from 2 tables that are on different databases. Currently I am able to populate the first entry, but it does not populate past that. here is the code:
void FillOrder(int inv)
{
var _ord = new OrdersContext();
var _pro = new ProductContext();
var qryOrder = (from o in _ord.OrderDetails
where o.InvNumberId == inv
select new
{
o.ProductID,
o.Quantity
}).ToList();
foreach (var order in qryOrder)
{
int prodID = order.ProductID;
int itemCount = qryOrder.Count;
var qryProducts = (from p in _pro.Products
where p.ProductID == prodID
select new
{
p.ProductID,
p.ProductName
}).ToList();
var results = (from t in qryOrder
join s in qryProducts
on t.ProductID equals prodID
select new
{
t.ProductID,
t.Quantity,
s.ProductName
}).ToList();
OrderItemList.DataSource = results;
OrderItemList.DataBind();
}
}
Can anyone help as to why it's only populating the first entry?

If the number of products involved is relatively small, (and since this query seems to be relate to one invoice, I would think that is true), then you can probably use something like the code below.
This is removing the loop, but the contains method will probably generate a SQL statement something like select ProductID, ProductName from products where productID in (,,,,,,) so may fail if the number of parameters is extremely large.
var _ord = new OrdersContext();
var _pro = new ProductContext();
var qryOrder = (from o in _ord.OrderDetails
where o.InvNumberId == inv
select new
{
o.ProductID,
o.Quantity
}).ToList();
// Get the productIDs
var productIDS = qryOrder.Select(o=>o.ProductID).Distinct().ToList();
// Get the details of the products used.
var qryProducts = (from p in _pro.Products
where productIDS.Contains(p.ProductID)
select new
{
p.ProductID,
p.ProductName
}).ToList();
// Combine the two in memory lists
var results = (from t in qryOrder
join s in qryProducts
on t.ProductID equals s.ProductID
select new
{
t.ProductID,
t.Quantity,
s.ProductName
}).ToList();
OrderItemList.DataSource = results;
OrderItemList.DataBind();

Join List Data from two separate Data Contexts

I have been searching for the solution to this problem and this is what I have so far:
var ProductInfo = (from p in twd.Products
orderby p.PC
where p.DELMARK == active
select p).AsEnumerable();
var BuyersData =
(from x in db.MinimumProductInfo
where x != null
orderby x.ItemCode, x.Region
let pnote =
(from pn in db.ProductNotes
where pn != null
where x.MinimumProductInfoID == pn.MinimumProductInfoID
&& pn.NoteTypeFlag == "p"
orderby pn.NoteDate descending
select pn).FirstOrDefault()
let cnote =
(from c in db.ProductNotes
where c != null
where x.MinimumProductInfoID == c.MinimumProductInfoID
&& c.NoteTypeFlag == "c"
orderby c.NoteDate descending
select c).FirstOrDefault()
let product =
(from p in ProductInfo
where x.ItemCode == p.PC
select p).FirstOrDefault()
select new ProductInfoWithNoteList
{
MinimumProductInfoID = x.MinimumProductInfoID,
ItemCode = x.ItemCode,
EquivCode = x.EquivCode,
Description = product.PDESC,
MinimumOnHandQuantity = x.MinimumOnHandQuantity,
MaximumOHandQuantity = x.MaximumOHandQuantity,
MinimumOrderQuantity = x.MinimumOrderQuantity,
LeadTimeInWeeks = x.LeadTimeInWeeks,
Region = x.Region,
Comment = cnote.ItemNote,
PermanentNote = pnote.ItemNote
}).ToArray();
It looks correct but I am getting an error,
'The specified LINQ expression contains references to queries that are
associated with different contexts.'
What this code is supposed to do is pull out all the active product codes from the first table using the twd datacontext then use data from that database in the db.MinimumProductInfo table. The reason they have 2 separate data contexts are they are completely different databases, the first is our ERP and the second is one that we are building in house.
What am I missing? I know it is possible to do this by separating the two datacontexts then adding them together because I have seen it done with single instances but I cannot find how to do it with list data.

Instead of this:
let product =
(from p in ProductInfo
where x.ItemCode == p.PC
select p).FirstOrDefault()
select new ProductInfoWithNoteList
{
MinimumProductInfoID = x.MinimumProductInfoID,
ItemCode = x.ItemCode,
EquivCode = x.EquivCode,
Description = product.PDESC,
MinimumOnHandQuantity = x.MinimumOnHandQuantity,
MaximumOHandQuantity = x.MaximumOHandQuantity,
MinimumOrderQuantity = x.MinimumOrderQuantity,
LeadTimeInWeeks = x.LeadTimeInWeeks,
Region = x.Region,
Comment = cnote.ItemNote,
PermanentNote = pnote.ItemNote
}).ToArray();
Try this by removing the let product clause and not filling the properties associated with ProductInfo because we will do that afterwards (See I have commented out the Description property):
select new ProductInfoWithNoteList
{
MinimumProductInfoID = x.MinimumProductInfoID,
ItemCode = x.ItemCode,
EquivCode = x.EquivCode,
//Description = product.PDESC,
MinimumOnHandQuantity = x.MinimumOnHandQuantity,
MaximumOHandQuantity = x.MaximumOHandQuantity,
MinimumOrderQuantity = x.MinimumOrderQuantity,
LeadTimeInWeeks = x.LeadTimeInWeeks,
Region = x.Region,
Comment = cnote.ItemNote,
PermanentNote = pnote.ItemNote
}).ToArray();
Now that you have your BuyersData and ProductInfo in memory, set the Description property or all the items in BuyersData:
foreach(var thisBuyerData in BuyersData)
{
var thisPi = ProductInfo.SingleOrDefault(x => x.PC == thisBuyerData.ItemCode);
thisBuyerData.Description = thisPi?.PDESC;
}

Creating table which changes a column in order to remove repeated values in rows

Sorry if the title was confusing.
Currently I am practicing with Entity Framework and LINQ expressions and got stuck on this.
I have a table with columns:"Personal ID", "Name", "Surname", "Phone ID" and all values on Phone ID are unique. I would like to create another table in which there would be same columns except for last being "Phone Count" which shows how many phones are associated with same Person(Personal ID). I want the table to show only 3 first highest count rows.
Here is the code i've wrote to make table that i've described above.
using (var db = new PRDatabaseEntities())
{
var query = from a in db.Person
join t in db.Repairs on a.PID equals t.Repairman_PID
orderby a.PID
select new
{
a.PID,
a.Name,
a.Surname,
t.Phone_ID
};
}

You could try with following group by LINQ query:
// First, generate a linq query
var query = from a in Persons
join t in Repairs on a.PID equals t.Repairman_PID
group new { a, t } by new { a.PID, a.Name, a.Surname } into g
select new
{
PID = g.Key.PID,
Name = g.Key.Name,
Surname = g.Key.Surname,
PhoneCount = g.Count()
};
// Then order by PhoneCount descending and take top 3 items
var list = query.OrderByDescending(t => t.PhoneCount).Take(3).ToList();

Try this:
using (var db = new PRDatabaseEntities())
{
var query = db.Person
.GroupJoin(db.Repairs,
p => p.PID, r => r.PID,
(p, r) => new {
PID = p.PID,
Name = p.Name,
Surname = p.Surname,
Count = r.Count()
};
}

associated data in linq select

I need to select data from different tables associated, I have a hospital table, another specialty, and other services, and what is held to select all hospitals and their specialties and services, there is a way to do this in linq?
this is what I'm trying
var hospitalesQuery = from hospital in App.ViewModel.ChristusDB.Hospitales
where hospital.id_tipo == "2" && hospital.christus == "1"
orderby hospital.distancia ascending
from e in App.ViewModel.ChristusDB.EspHosp
where e.fk_hospital==hospital.pk_hospital
from s in App.ViewModel.ChristusDB.ServHosp
where s.fk_hospital==hospital.pk_hospital
select new Hospitale()
{
pk_hospital = hospital.pk_hospital,
nombre = hospital.nombre,
direccion = hospital.direccion,
ciudad = hospital.ciudad,
id_ciudad = hospital.id_ciudad,
estado = hospital.estado,
id_estado = hospital.id_estado,
id_tipo = hospital.id_tipo,
tipo_descripcion = hospital.tipo_descripcion,
imagen = hospital.imagen,
gps_lat = hospital.gps_lat,
gps_lng = hospital.gps_lng,
abierto_lv = hospital.abierto_lv,
abierto_sd = hospital.abierto_sd,
telefono_1 = hospital.telefono_1,
telefono_2 = hospital.telefono_2,
telefono_3 = hospital.telefono_3,
telefono_4 = hospital.telefono_4,
telefono_5 = hospital.telefono_5,
inactivo = hospital.inactivo,
christus = hospital.christus,
especialidades= new List<Especialidade>(e),
servicios= new List<Servicio>(s)
};

You are looking for joining tables by a foreign key. LINQ (asn SQL as well) provide join for this:
from hospital in App.ViewModel.ChristusDB.Hospitales
where hospital.id_tipo == "2" && hospital.christus == "1"
join e in App.ViewModel.ChristusDB.EspHosp on hospital.pk_hospital equals e.fk_hospital
join s in App.ViewModel.ChristusDB.ServHosp on hospital.pk_hospital on s.fk_hospital
orderby hospital.distancia ascending
select new Hospitale()
{...
Update. If you want to load list dependencies for each of the hospitals, I do not think you can do this with one query in EF. This is as close as you can get:
var hospitals = (from hospital in App.ViewModel.ChristusDB.Hospitales
where hospital.id_tipo == "2" && hospital.christus == "1"
orderby hospital.distancia ascending
select new Hospitale()
{
pk_hospital = hospital.pk_hospital,
...
}).ToList();
foreach (var h in hospitals)
{
h.especialidades = App.ViewModel.ChristusDB.EspHosp.Where(e => e.fk_hospital==h.pk_hospital).ToList();
h.servicios = App.ViewModel.ChristusDB.ServHosp.Where(e => s.fk_hospital==h.pk_hospital).ToList();
}
However this would be a lot of queries to the DB, which might perform poorly. You should really think about redesigning your EF data model properly so that the framework does this job of loading dependencies for you.