var queryResult = this.kindergardenDataContext.Groups.Where(g => g.group_id == groupToAdd.group_id && g.group_enabled==true);
if (queryResult != null && queryResult.Count() != 0)
{
Group groupToEdit = queryResult.First();
groupToEdit.group_name = groupToAdd.group_name;
groupToEdit.group_create_date = groupToAdd.group_create_date;
groupToEdit.Kindergarden = groupToAdd.Kindergarden;
groupToEdit.GroupGuardian = groupToAdd.GroupGuardian;
groupToEdit.Room = groupToAdd.Room;
}
this.kindergardenDataContext.SubmitChanges();
Hi. Im beginner in LINQ. Here is ok, but foreigns key kindergarden, groupguardian, room has been duplicated in database (added new rows in database in kindergarden, groupguardian, room table). How can I set good reference to update row in group table.
Unless you retrieved groupToAdd.Kindergarden, groupToAdd.GroupGuardian, andgroupToAdd.Roomfromthis.kindergardenDataContext` or attached them with the right IDs set, that is the expected behviour. It doesn't know that you mean the same object instances that already resides in the database.
Related
I have a var variable where it has set of objects. I want to query a particular object and hide/delete 2 rows based on ID.
I am trying to select the value as below but still it is not working. Any help is greatly appreciated.
var getTransformDetails = contentView.Package; if(totalCost > 100000) { getTransformDetails.AnnualPaymentGrid.Where(x => x.Id != XXXXX1 || x.Id != XXXXX2); }
I use Linq to Sql.
I have three table.
tabl_Region: from this table returning .ToList() via county column == 85
tabl_Season: from this table returning .ToList() via startdate >= today
tabl_Desc: from this table returning int [] ID via fldRegion== 1 results && fldSeason== 2 results
I will try to explain not worked codes
TurkusEntities context = new TurkusEntities();
return context.tabl_AttrDesc.Where(c => c.fldRegionId == context.tabl_Region.Where(r => r.fldCounty == 85).ToList() && c.fldSeasonId == context.tabl_Season.Where(s => s.fldStartDate >= DateTime.Now).ToList()).ToList;
I know i can solve it by using loops, but if it is possible i want to use only query.
If you are using Linq2Sql you can get the
sql that is generated by a linq query. with this command.
dc.GetCommand(query).CommandText
If you are using SQL Server Profiler inside the Sql Server (Tools --> SQL Server Profiler)
I found solution but not impossible in one query.
First I got int [] ID arrays which match conditions from two tables.After I wrote a query which provide control column data from arrays.
TurkusEntities context = new TurkusEntities();
Region region = new Region();
string[] dataarray = region.GetAllRegionsBySomeRule(RegionX);
var _db= context.tabl_AttrDesc.Where(c =>dataarray.Contains(c.fldRegionId.ToString().Trim())).ToList();
And Region
public string[] GetAllRegionsBySomeRule(int fldType,int fldRegionX)
{
TurkusEntities context = new TurkusEntities();
var _db = context.tabl_Region.Where(c => c.fldTown.Contains(fldRegionX.ToString())).ToList();
foreach (var data in _db)
{
Regions.Add(data.fldId.ToString().Trim());
}
string[] IDS = Regions.ToArray();
return IDS;
}
I have the following LINQ query using EF5 and generic repository, unit of work patterns to a SQL Server 2008 db
var countriesArr = GetIdsFromDelimStr(countries);
var competitionsArr = GetIdsFromDelimStr(competitions);
var filterTeamName = string.Empty;
if (teamName != null)
{
filterTeamName = teamName.ToUpper();
}
using (var unitOfWork = new FootballUnitOfWork(ConnFooty))
{
// give us our selection of teams
var teams =
(from team in
unitOfWork.TeamRepository.Find()
where ((string.IsNullOrEmpty(filterTeamName) || team.Name.ToUpper().Contains(filterTeamName)) &&
(countriesArr.Contains(team.Venue.Country.Id) || countriesArr.Count() == 0))
select new
{
tId = team.Id
}).Distinct();
// give us our selection of contests
var conts = (
from cont in
unitOfWork.ContestRepository.Find(
c =>
((c.ContestType == ContestType.League && competitionsArr.Count() == 0) ||
(competitionsArr.Contains(c.Competition.Id) && competitionsArr.Count() == 0)))
select new
{
contId = cont.Id
}
).Distinct();
// get selection of home teams based on contest
var homecomps = (from fixt in unitOfWork.FixtureDetailsRepository.Find()
where
teams.Any(t => t.tId == fixt.HomeTeam.Id) &&
conts.Any(c => c.contId == fixt.Contest.Id)
select new
{
teamId = fixt.HomeTeam.Id,
teamName = fixt.HomeTeam.Name,
countryId = fixt.HomeTeam.Venue.Country.Id != null ? fixt.HomeTeam.Venue.Country.Id : 0,
countryName = fixt.HomeTeam.Venue.Country.Id != null ? fixt.HomeTeam.Venue.Country.Name : string.Empty,
compId = fixt.Contest.Competition.Id,
compDesc = fixt.Contest.Competition.Description
}).Distinct();
// get selection of away teams based on contest
var awaycomps = (from fixt in unitOfWork.FixtureDetailsRepository.Find()
where
teams.Any(t => t.tId == fixt.AwayTeam.Id) &&
conts.Any(c => c.contId == fixt.Contest.Id)
select new
{
teamId = fixt.AwayTeam.Id,
teamName = fixt.AwayTeam.Name,
countryId = fixt.AwayTeam.Venue.Country.Id != null ? fixt.AwayTeam.Venue.Country.Id : 0,
countryName = fixt.AwayTeam.Venue.Country.Id != null ? fixt.AwayTeam.Venue.Country.Name : string.Empty,
compId = fixt.Contest.Competition.Id,
compDesc = fixt.Contest.Competition.Description
}).Distinct();
// ensure that we return the max competition based on id for home teams
var homemax = (from t in homecomps
group t by t.teamId
into grp
let maxcomp = grp.Max(g => g.compId)
from g in grp
where g.compId == maxcomp
select g).Distinct();
// ensure that we return the max competition based on id for away teams
var awaymax = (from t in awaycomps
group t by t.teamId
into grp
let maxcomp = grp.Max(g => g.compId)
from g in grp
where g.compId == maxcomp
select g).Distinct();
var filteredteams = homemax.Union(awaymax).OrderBy(t => t.teamName).AsQueryable();
As you can see we want to return the following format which is passed across to a WebAPI so we cast the results to types we can relate to in the UI.
Essentially what we are trying to do is get the home and away teams from a fixture, these fixtures have a contest which relates to a competition. We then get the highest competition id from the grouping and then this is returned with that team. The country is related to the team based on the venue id, when I was originally doing this i had problems figuring out how to do OR joins in linq which is why i split it down to getting home teams and away team and then grouping them based on competition then unioning them together.
An idea of current table size is fixtures has 7840 rows, teams has 8581 rows, contests has 337 rows and competitions has 96 rows. The table that is likely to increase rapidly is the fixture table as this is related to football.
The output we want to end up with is
Team Id, Team Name, Country Id, Country Name, Competition Id, Competition Name
Using no filtering this query takes on average around 5 secs, just wondering if anybody has any ideas/pointers on how to make it quicker.
thanks in advance Mark
I can't judge whether it will speed up things, but your homemax and awaymax queries could be
var homemax = from t in homecomps
group t by t.teamId into grp
select grp.OrderByDescending(x => x.compId).FirstOrDefault();
var awaymax = from t in awaycomps
group t by t.teamId into grp
select grp.OrderByDescending(x => x.compId).FirstOrDefault();
Further, as you are composing one very large query it may perform better when you cut it up in a few smaller queries that fetch intermediary results. Sometimes a few more roundtrips to the database perform better than one very large query for which the database engine can't find a good execution plan.
Another thing is all these Distinct()s. Do you always need them? I think you can do without because you are always fetching data from one table without joining a child collection. Removing them may save a bunch.
Yet another optimization could be to remove the ToUpper. The comparison is done by the database engine in SQL and chances are that the database has a case-insensitive collation. If so, the comparison is never case sensitive even if you'd want it to be! Constructs like Name.ToUpper cancel the use of any index on Name (it is not sargable).
I've an 'product' object that has to update a record in db.
Through a 'productCode' I retrieve the object to update using Linq.
Which is the most elegant way to overwrite alle the property but not the key one and then save changes?
You will need to access each property anyways, as you fetch a record manually. my recommendation for easiest, fastest and cleanest code:
code = productCode_toChange
using(Entity ent = new Entity())
{
var update = (from x in ent.Products where x.productCode == code select x).First();
update.property1 = product.property1;
update.property2 = product.property2;
// and so on for each property you change
ent.SaveChanges();
}
you could of course try:
using(Entity ent = new Entity())
{
var update = (from x in ent.Products where x.productCode == code select x).First();
update = product;
ent.SaveChanges();
}
but i can almost guarantee this will not work, as product will certainly have an id-property it will try to write to update, which will throw an exception, given the case product is the LINQ-generated type for the table-instance.
Be careful to check for type-conformity. also note, that you the SQL-Type of product code should not be text, as this type is incomparable
I am looking to optimize my LINQ query because although it works right, the SQL it generates is convoluted and inefficient...
Basically, I am looking to select customers (as CustomerDisplay objects) who ordered the required product (reqdProdId), and are registered with a credit card number (stored as a row in RegisteredCustomer table with a foreign key CustId)
var q = from cust in db.Customers
join regCust in db.RegisteredCustomers on cust.ID equals regCust.CustId
where cust.CustomerProducts.Any(co => co.ProductID == reqdProdId)
where regCust.CreditCardNumber != null && regCust.Authorized == true
select new CustomerDisplay
{
Id = cust.Id,
Name = cust.Person.DisplayName,
RegNumber = cust.RegNumber
};
As an overview, a Customer has a corresponding Person which has the Name; PersonID is a foreign key in Customer table.
If I look at the SQL generated, I see all columns being selected from the Person table. Fyi, DisplayName is an extension method which uses Customer.FirstName and LastName. Any ideas how I can limit the columns from Person?
Secondly, I want to get rid of the Any clause (and use a sub-query) to select all other CustomerIds who have the required ProductID, because it (understandably) generates an Exists clause.
As you may know, LINQ has a known issue with junction tables, so I cannot just do a cust.CustomerProducts.Products.
How can I select all Customers in the junction table with the required ProductID?
Any help/advice is appreciated.
The first step is to start your query from CustomerProducts (as Alex Said):
IQueryable<CustomerDisplay> myCustDisplay =
from custProd in db.CustomerProducts
join regCust in db.RegisteredCustomers
on custProd.Customer.ID equals regCust.CustId
where
custProd.ProductID == reqProdId
&& regCust.CreditCardNumber != null
&& regCust.Authorized == true
select new CustomerDisplay
{
Id = cust.Id,
Name = cust.Person.Name,
RegNumber = cust.RegNumber
};
This will simplify your syntax and hopefully result in a better execution plan.
Next, you should consider creating a foreign key relationship between Customers and RegisteredCustomers. This would result in a query that looked like this:
IQueryable<CustomerDisplay> myCustDisplay =
from custProd in db.CustomerProducts
where
custProd.ProductID == reqProdId
&& custProd.Customer.RegisteredCustomer.CreditCardNumber != null
&& custProd.Customer.RegisteredCustomer.Authorized == true
select new CustomerDisplay
{
Id = cust.Id,
Name = cust.Person.Name,
RegNumber = cust.RegNumber
};
Finally, for optimum speed, have LINQ compile your query at compile time, rather than run time by using a compiled query:
Func<MyDataContext, SearchParameters, IQueryable<CustomerDisplay>>
GetCustWithProd =
System.Data.Linq.CompiledQuery.Compile(
(MyDataContext db, SearchParameters myParams) =>
from custProd in db.CustomerProducts
where
custProd.ProductID == myParams.reqProdId
&& custProd.Customer.RegisteredCustomer.CreditCardNumber != null
&& custProd.Customer.RegisteredCustomer.Authorized == true
select new CustomerDisplay
{
Id = cust.Id,
Name = cust.Person.Name,
RegNumber = cust.RegNumber
};
);
You can call the compiled query like this:
IQueryable<CustomerDisplay> myCustDisplay = GetCustWithProd(db, myParams);
I'd suggest starting your query from the product in question, e.g. something like:
from cp in db.CustomerProducts
join .....
where cp.ProductID == reqdProdID
As you have found, using a property defined as an extension function or in a partial class will require that the entire object is hydrated first and then the select projection is done on the client side because the server has no knowledge of these additional properties. Be glad that your code ran at all. If you were to use the non-mapped value elsewhere in your query (other than in the projection), you would likely see a run-time exception. You can see this if you try to use the Customer.Person.DisplayName property in a Where clause. As you have found, the fix is to do the string concatenation in the projection clause directly.
Lame Duck, I think there is a bug in your code as the cust variable used in your select clause isn't declared elsewhere as a source local variable (in the from clauses).