List<Post> list =
(
from c in db.TitleComments
join t in db.Titles on c.TitleId equals t.Id
join u in db.Users on c.UserId equals u.Id
where t.Id == _titleId && c.Date > time
orderby c.Date descending
select new Post { Username = u.Username, PostingDate = c.Date.ToString(), Data = c.Comment }
).ToList();
The code above causes exception on the convertion of date to string, PostingDate = c.Date.ToString(). Any ideas how to get around this?
Exception error:
{"LINQ to Entities does not recognize the method 'System.String ToString()' method, and this method cannot be translated into a store expression."}
linq is trying to convert date to string using sql but since there is no ToString() method in sql it can't convert it, this behavior is by design - Joakim
In other words, return the date itself and convert it to a string after it executes on SQL side:
(
select new { Username = u.Username,
PostingDate = c.Date
[...]
})
.ToList() // runs on SQL and returns to the application
.Select(o => // is not generating a SQL, it is running on the app
new Post { Username = o.Username,
PostingDate = o.PostingDate.ToString(),
[...]
})
You can remedy your problem by projecting into an anonymous type, and then at a later step project into Post after the data has already been returned from the DB.
(from ....
select new { /* stuff */, Date = c.Date })
.AsEnumerable()
.Select(p => new Post { /* stuff */, PostingDate = p.Date.ToString() })
.ToList();
However, given that you have a property called PostingDate, the original source being a date, I would recommend your revise your object to actually keep the value as a DateTime instead of a string.
I dont think this can be done in a direct way.
var list =
select new Post { Username = u.Username, PostingDate = SqlFunctions.StringConvert(c.Date), Data = c.Comment }
from
(from c in db.TitleComments
join t in db.Titles on c.TitleId equals t.Id
join u in db.Users on c.UserId equals u.Id
where t.Id == _titleId && c.Date > time
orderby c.Date descending).AsEnumerable()
).ToList();
Also with EF4 you can try something like this:
List<Post> list =
(
from c in db.TitleComments
join t in db.Titles on c.TitleId equals t.Id
join u in db.Users on c.UserId equals u.Id
where t.Id == _titleId && c.Date > time
orderby c.Date descending
select new Post { Username = u.Username, PostingDate = SqlFunctions.DateName(c.Date), Data = c.Comment }
).ToList();
Related
In this linq query I need to apply where condition for selecting only tiertype .I have tried the following but getting error in the where condition of tiertype.The error is "ti in ti.ImageVersion ti does not exist in current context.
var result = (from p in _context.Product
join ti in _context.TierImageMap on p.Id equals ti.ProductId
join t in _context.Tiers on ti.TierType equals t.Id
where (p.Id == productname)
orderby ti.ReleaseVersion descending
group new { ti, t } by new { ti.ImageName, t.TierType,ti.ImageVersion } into cities
select new
{
ReleaseVersion = string.Join(",", (from n in cities select n.ti.ReleaseVersion).Distinct().Take(3)),
ImageName = string.Join(",", (from n in cities select n.ti.ImageName).Distinct()),
TierType = string.Join(",", (from n in cities select n.t.TierType).Where(ti.ImageVersion== imageversion).Distinct())
//String.Format(ti.ReleaseVersion, ", ").GroupBy.OrderByDescending( ti.ImagDESeName ) as Releaseversion,
//String.Format(t.TierType, ", ").GroupBy.OrderByDescending( ti.ImageName ) as Tiertype
}).ToList().Distinct();
await _context.SaveChangesAsync();
I'm trying to fetch the record from 3 tables by comparing the user Logged in name
Here is my code:
public ActionResult MeritList() //departmental merit listed students details with status 1
{
var username= HttpContext.Session["UserName"];
List<StdListModel> model = new List<StdListModel>();
var query = (from s in Context.tblStdDetails
join e in Context.tblStdEnrollments on s.ID equals e.StdReg_ref_id
//join d in Context.tblDepartments on e.Depart_ref_id equals d.ID
where s.Status == '1' && e.tblDepartment.DepartName == username
select new StdListModel
{
ID = s.ID,
Name = s.Name,
FatherName = s.FatherName,
CNIC = s.CNIC,
FormNo = s.FormNo,
DiaryNo = s.DiaryNo,
Status = s.Status
}).ToList();
foreach(var item in query)
{
model.Add(new StdListModel()
{
ID=item.ID,
Name=item.Name,
FatherName=item.FatherName,
CNIC=item.CNIC,
FormNo=item.FormNo,
DiaryNo=item.DiaryNo
});
}
return View(model);
}
Also Tried this Query
var query = (from s in Context.tblStdDetails
join e in Context.tblStdEnrollments on s.ID equals e.StdReg_ref_id
join d in Context.tblDepartments on e.Depart_ref_id equals d.ID
where s.Status == '1' && d.DepartName.Equals(username)
select new StdListModel
{
ID = s.ID,
Name = s.Name,
FatherName = s.FatherName,
CNIC = s.CNIC,
FormNo = s.FormNo,
DiaryNo = s.DiaryNo,
Status = s.Status
}).ToList();
But it does not return anything model=0, query =0, the database has right values and I don't get any error either.
please check username with tolower() and trim function.
e.tblDepartment.DepartName.ToLower().Trim() == username.ToLower().Trim()
or
e.tblDepartment.DepartName.ToLower().Trim().equals(username.ToLower().Trim())
I got the problem. It is in
s.Status == '1'
I just changed it into
s.Status == 1
and it works fetch the data from the database.
I have a LINQ to Entities Query that is suppose to return a specific resultset based on the GUID provided.
[OperationContract, WebGet(ResponseFormat = WebMessageFormat.Json)]
public List<OrderDetails> GetOrderDetailsByGUID(Guid OrderID)
{
var listit =(from OV in EC.OrderProductVariants
join O in EC.Orders on OV.OrderId equals O.Id
join PV in EC.ProductVariants on OV.ProductVariantId equals PV.Id
join P in EC.Products on PV.ProductId equals P.Id
join CT in EC.Customers on O.CustomerId equals CT.Id
join AD in EC.Addresses on CT.BillingAddress_Id equals AD.Id
where O.OrderGuid == OrderID
select new OrderDetails
{
OrderID = O.OrderGuid,
Company = AD.Company,
ShippingMethod = O.ShippingMethod,
Product = P.Name,
QuantityOnOrder = OV.Quantity
}
).ToList();
return listit;
}
It Returns NULL, can anyone tell me what I am doing wrong?
All solution that could work in a scenario like this is to create a view and do just a one liner code to access it
var q = EC.OrderProductVariants.SingleOrDefault(u => u.OrderGuid.Equals(guid));
I got this in the controller
var tobi = (from a in db.Assessments
join u in db.Users on a.rated equals u.user_id
join tm in db.Team_Members on u.user_id equals tm.user_id
join t in db.Teams on tm.team_id equals t.team_id
where (tm.end_date == null || tm.end_date > DateTime.Today)
group new TobiViewModel
{
teamname = t.name,
assessed_due = a.assessed_due,
assessment_id = a.assessment_id,
rater = a.rater,
rated = a.rated
}
by new { t.name, a.rated }).ToList();
return View(tobi);
But then it doesn't accept it in the view?
The model item passed into the dictionary is of type
'System.Collections.Generic.List1[System.Linq.IGrouping2[<>f__AnonymousType102[System.String,System.String],Kyubu.ViewModels.TobiViewModel]]',
but this dictionary requires a model item of type
'System.Collections.Generic.IEnumerable1[Kyubu.ViewModels.TobiViewModel]'.
how should i pass this in the view. Any help would be appreciated
The type in the view is
#model IEnumerable<Kyubu.ViewModels.TobiViewModel>
Try the following in the view:
#model IEnumerable<System.Linq.IGrouping<object, Kyubu.ViewModels.TobiViewModel>>
Hi guys i need to replicate this SQL query in Linq to Entity
select * from Subscriber a
inner join User b on a.UserId = b.Id
where b.Username = 'Name'
May be some one may help.
Try this:
var query = from s in context.Subscribers.Include("User")
where s.User.Username == "Name"
select s;
This suppose that Subscriber has navigation property User referencing the user instance.
If you wan to use join (which is not needed) you can use this for inner join:
var query = from s in context.Subscribers
join u in context.Users on s.User.Id equals u.Id
where u.Username == "Name"
select new
{
Subscriber = s,
User = u
};
or this for left outer join:
var query = from s in context.Subscribers
join u in context.Users on s.User.Id equals u.Id into x
where u.Username == "Name"
from y in x.DefaultIfEmpty()
select new
{
Subscriber = s
User = y,
};