I have the following SQL command:
SELECT CONVERT(varchar, Logged, 103) AS Visited, COUNT(ID) AS Totals
FROM tblStats
GROUP BY CONVERT(varchar, Logged, 103)
ORDER BY Visited DESC
I want to translate this into a L2S statement that can be used with the Entity Framework, but in working with datetime types, I'm getting various errors depending on how I try to attack the problem.
Approach:
var results = from s in db.Stats
group s by (s.Logged.Date.ToString()) into Grp
select new { Day = Grp.Key, Total = Grp.Count() };
Error:
LINQ to Entities does not recognize
the method 'System.String ToString()'
method, and this method cannot be
translated into a store expression.
Approach:
var results = from s in db.Stats
group s by (s.Logged.Date) into Grp
select new { Day = Grp.Key, Total = Grp.Count() };
Error:
The specified type member 'Date' is
not supported in LINQ to Entities.
Only initializers, entity members, and
entity navigation properties are
supported.
What syntax do I need to make the query work?
Try using the EntityFunctions.TruncateTime method:
var results = from s in db.Stats
group s by EntityFunctions.TruncateTime(s.Logged) into Grp
select new { Day = Grp.Key, Total = Grp.Count() };
Do you need the Date section in s.Logged.Date?
Have you tried this:
var results = from s in db.Stats
group s by (s.Logged) into Grp
select new { Day = Grp.Key, Total = Grp.Count() };
I'm assuming that Logged is the property (column in the table).
EDIT: you guys are way to quick.
Related
I'm new in MVC and in using LINQ. I'm trying to join 3 tables on my project. These are my tables.
Client table,
Event table,
Register table,
This my linq statement,
OnlineRegistrationDBEntities1 dbClient = new OnlineRegistrationDBEntities1();
OnlineRegistrationDBEntities1 dbEvents = new OnlineRegistrationDBEntities1();
OnlineRegistrationDBEntities1 dbRegEvents = new OnlineRegistrationDBEntities1();
var displayRegisteredEvents = from x in dbRegEvents.Registers
join c in dbClient.clients on x.email equals c.email
join e in dbEvents.events on x.eventname equals e.eventname
select new
{
fullname = c.fullname,
eventname = e.eventname,
email = c.email,
guestnumber = x.guestnumber,
payment_amount = x.payment_amount
};
ViewBag.viewRegisteredEvents = displayRegisteredEvents;
return View();
I'm trying to show the results on a table format in my view like this,
But when I run the program I got this error, The specified LINQ expression contains references to queries that are associated with different contexts. Thank you so much for the help.
I did raw SQL query below to select only certain fields from a table.
{
List<CustEmpVM> CustomerVMlist = new List<CustEmpVM>();
var cid = db.Customers.SqlQuery("select SchedDate from Customer where CustID = '#id'").ToList<Customer>();
}
But i keep getting the error of:
System.Data.Entity.Core.EntityCommandExecutionException occurred in EntityFramework.SqlServer.dll but was not handled in user code
Additional information: The data reader is incompatible with the specified ALFHomeMovers.Customer. A member of the type, CustID, does not have a corresponding column in the data reader with the same name.
The exception message is pretty straightforward: the query expected to return full entity of Customer table but only SchedDate column returned, hence EF cannot done mapping other omitted columns including CustID.
Assuming Customers is a DbSet<Customer>, try return all fields from Customer instead:
// don't forget to include SqlParameter
var cid = db.Customers.SqlQuery("SELECT * FROM Customer WHERE CustID = #id",
new SqlParameter("id", "[customer_id]")).ToList();
If you want just returning SchedDate column, materialize query results and use Select afterwards:
var cid = db.Customers.SqlQuery("SELECT * FROM Customer WHERE CustID = #id",
new SqlParameter("id", "[customer_id]"))
.AsEnumerable().Select(x => x.SchedDate).ToList();
NB: I think you can construct LINQ based from the SELECT query above:
var cid = (from c in db.Customers
where c.CustID == "[customer_id]"
select c.SchedDate).ToList();
Similar issue:
The data reader is incompatible with the specified Entity Framework
Use below query instead of raw query:
{
List<CustEmpVM> CustomerVMlist = new List<CustEmpVM>();
var cid = db.Customers.Where(w=>w.Id == YOURCUSTOMERID).Select(s=>new Customer{SchedDate = s.SchedDate }).ToList();
}
It will give compile time error rather than run time error.
In my Person table is a RequestedLocation column which stores location IDs. The IDs match the LocationId column in the Locations table, the Locations table also has the text location names, in the LocatioName column.
In my view, I need to display the string LocationName in the view which has the Person model passed to it. The view will be displaying a List of people in a telerik grid. CUrrently it works great, except the RequestedLocation column is all integers.
I am populating all my grids with methods containing LINQ queries. Here is the method that currently works:
public List<Person> GetPeople()
{
var query = from p in _DB.Person.ToList()
select p;
return query.ToList();
}
Here is the regular SQL query that works, and I need to convert into LINQ:
SELECT ApplicantID
,FirstName
,LastName
,MiddleName
,DateofBirth
,Gender
,RequestedVolunteerRole
,RequestedVolunteerLocation
,l.LocationName
FROM Form.Person p
JOIN dbo.Location l ON p.RequestedVolunteerLocation = l.LocationID
Order BY ApplicantID
Here is my attempt to convert to LINQ:
public List<NewApplicantViewModel> GetPeople()
{
var query = from pl in _DB.Person.ToList()
join l in _Elig_DB.Locations.ToList() on pl.RequestedVolunteerLocation equals l.LocationID
select new
{
pl.RequestedVolunteerLocation = l.LocationName
};
return query.ToList();
The number of errors I get from this are numerous, but most are along the lines of:
Cannot convert from type Annonymous to Type List<NewAPplicantModel>
and
Invalid annonymous type declarator.
Please help, and thank you for reading my post.
Oh, and I have only been programming for a couple months, so if I am going about this all wrong, please let me know. Only thing I have to stick with is the table structure because it is an existing app that I am updating, and changing the location or person tables would have large consequences.
public List<NewApplicantViewModel> GetPeople()
{
var query = from pl in _DB.Person
join l in _Elig_DB.Locations on pl.RequestedVolunteerLocation
equals l.LocationID
select new NewApplicantViewModel
{
LocationName = l.LocationName,
otherPropery = p.Property
};
return query.ToList();
}
Beware of calling _DB.Person.ToList() it will load all persons from DB because ToList() immediately executes the query and the join would be performed in memory (not in DB).
The reason you are getting an error is you are projecting an anonymous type
select new
{
pl.RequestedVolunteerLocation = l.LocationName
};
Instead, you need to project a NewApplicantViewModel
select new NewApplicantViewModel
{
RequestedVolunteerLocation = l.LocationName
};
I am trying to write a query that includes 2 joins.
1 StoryTemplate can have multiple Stories
1 Story can have multiple StoryDrafts
I am starting the query on the StoryDrafts object because that is where it's linked to the UserId.
I don't have a reference from the StoryDrafts object directly to the StoryTemplates object. How would I build this query properly?
public JsonResult Index(int userId)
{
return Json(
db.StoryDrafts
.Include("Story")
.Include("StoryTemplate")
.Where(d => d.UserId == userId)
,JsonRequestBehavior.AllowGet);
}
Thank you for any help.
Try to flatten your hierarchy if it works for you. Here is a sample, and you may want to customize it for your needs.
var result = from c in db.Customers
join o in db.Orders
on c equals o.Customers
select new
{
custid = c.CustomerID,
cname = c.CompanyName,
address = c.Address,
orderid = o.OrderID,
freight = o.Freight,
orderdate = o.OrderDate
};
If flattering does not meet your requirements then you need to use query that returns a Nested Group. Finally, look at the following link for more references - LINQ Query Expressions .
I have created a set of search results, and I wish to create a filter of available cats, with the number of results within that filter. however I get the most strangest error when trying to do this.
Unable to create a constant value of type 'NAMESPACE.Models.Products'. Only primitive types ('such as Int32, String, and Guid') are supported in this context.
this is the code i have tried:
var cats = (from p in ctx1.SubCategories
where myCats.Contains(p.subCategoryId) && p.enabled
select new
AvailableSubCats
{
CategoryName = p.subCategoryName,
Id = p.subCategoryId,
TotalItems = model.Count(x => x.subCategoryId == p.subCategoryId)
}).Distinct();
Products is the object that is called model on the line of totalItems.
I have also tried this:
var cats = from c in ctx1.SubCategories
join p in model on c.subCategoryId equals p.subCategorySubId
group p by c.subCategoryName
into g
select new
AvailableSubCats
{
CategoryName = g.Key,
Id = 0,
TotalItems = g.Count()
};
with the same error, and dont like this because i dont know how to get the name of the category and its ID.
help much appreciated.
thanks
p.s I am using Entity framework 4.1, .net 4 and MVC 3, mysql
in short i am trying to run this in linq, but were the the products side is already a result
select c.*, (select count(productId) from Products where Products.subCategoryId = c.subCategoryId) as counter from SubCategories c
You could try turning your list of products into a list of subCategoryId's so EF can understand it. Something like:
var subCategoryIds = model.Select(m => m.subCategoryId);
var cats = (from p in ctx1.SubCategories
ctx1.SubCategories
where myCats.Contains(p.subCategoryId) && p.enabled
select new
AvailableSubCats
{
CategoryName = p.subCategoryName,
Id = p.subCategoryId,
TotalItems = subCategoryIds.Count(x => x == p.subCategoryId)
}).Distinct();