When i use y in my select it has "Nullable object must have a value" error
var products = productQuery.
.GroupJoin(customerProductPrices,
p => p.Id,
pp => pp.ProductId,
(p, pp) => new { Product = p, CustomerProductPrice = pp })
.SelectMany(
x => x.CustomerProductPrice.DefaultIfEmpty(),
(x, y) => new ProductFilterResultModel
{
Id = x.Product.Id,
Price = y != null ? y.Price : 0
});
I don't know what is your GroupJoin purpose? I don't have entities, from the example I can rewrite:
var products = customerProductPrices.Select(pp => new ProductFilterResultModel
{
Id = pp.Product.Id,
Price = pp != null ? pp.Price : 0
})
I found the error,
Thats because of my ProductFilterResultModel model, some properties in this model was not nullable but the datas which fetch from database and related to these properties was null. I change my nullable properties required type to the nullable type.
Related
I have this query:
Project = await Context.Projects.Where(x => x.Id == project.Id)
.Select(x => new ProjectModel
{
Id = project.Id,
Name = project.Name,
TreeDataDict = x.Tasks.Select(y => new TreeItemModel()
{
NodeId = y.Id,
ParentId = SetTaskParentId(y, y.Type),
NodeTitle = y.Name,
Expanded = false,
Object = new TaskBaseModel
{
Milestone = y.Milestone,
StartDate = y.StartDate,
CurrentEndDate = y.CurrentEndDate,
EndDate = y.EndDate,
},
Icon = TaskHelper.GetTaskIcon(y.Type),
Children = new List<TreeItemModel>()
}).ToDictionary(y => y.NodeId, y => y)
}).SingleOrDefaultAsync();
and also tried like this:
Project = await Context.Projects.Where(x => x.Id == project.Id)
.Select(x => new ProjectModel
{
Id = project.Id,
Name = project.Name,
TreeDataDict = x.Tasks.ToDictionary(y => y.Id, y => new TreeItemModel(
{
NodeId = y.Id,
ParentId = SetTaskParentId(y, y.Type),
NodeTitle = y.Name,
Expanded = false,
Object = new TaskBaseModel
{
Milestone = y.Milestone,
StartDate = y.StartDate,
CurrentEndDate = y.CurrentEndDate,
EndDate = y.EndDate,
},
Icon = TaskHelper.GetTaskIcon(y.Type),
Children = new List<TreeItemModel>()
})
}).SingleOrDefaultAsync();
Both ways I got this exception:
What could be causing this? and is there a way I could make this work without fetching as a list and then covert it to dictionary? What could be the most efficient way to achieve this?
Regards
What could be causing this?
Translation of the nested ToDictionary call (none of the available overloads) is not supported. Consider it one of the (many) current (latest at the time of writing official v5.0.11) EF Core shortcomings.
Interestingly though, the Dictionary<TKey, TValue> constructor overload with IEnumerable<KeyValuePair<TKey, TValue>> argument as well as projection (Select) to KeyValuePair<TKey, TValue> is supported, which gives the workaround - replace the ToDictionary call with the aforementioned constructor and Select, e.g. (replace int with the type of the Id)
TreeDataDict = new Dictionary<int, TreeItemModel>(
x.Tasks.Select(y => new TreeItemModel()
{
NodeId = y.Id,
ParentId = SetTaskParentId(y, y.Type),
NodeTitle = y.Name,
Expanded = false,
Object = new TaskBaseModel
{
Milestone = y.Milestone,
StartDate = y.StartDate,
CurrentEndDate = y.CurrentEndDate,
EndDate = y.EndDate,
},
Icon = TaskHelper.GetTaskIcon(y.Type),
Children = new List<TreeItemModel>()
})
.Select(e => new KeyValuePair<int, TreeItemModel>(e.NodeId, e)));
This will fix the current error. But note that you are using other non-translatable constructs (custom method calls like SetTaskParentId(y, y.Type) and TaskHelper.GetTaskIcon(y.Type)) which are supported only in the final Select, so make sure to not add LINQ operator like Where, OrderBy etc. after the root query Select(x => new ProjectModel { ... }, otherwise you'll get other runtime errors. ToList, `First
I am new in EF and LINQ and I am facing a strange issue. When I check null value in my select new block, all values from child table is coming null. Below is the LINQ query.
My Linq Code
var linqResult = from pd in entities.tblpackagedetails
join ps in entities.tblpackageselecteds
on pd.PackageDetailsID equals ps.PackageDetailsID
into tabJoin
from tj in tabJoin.Where(ps => ps.UserID == userID
&& ps.IsActive == true).DefaultIfEmpty()
select new
{
IsComplete = (tj == null) ? false : tj.IsComplete,
IsActive = (tj == null) ? false : tj.IsActive,
UserID = (tj == null) ? 0 : tj.UserID,
IsMandatory = pd.IsMandatory,
PackageSelectedID = (tj == null) ? 0 : tj.PackageSelectedID,
IsSelected = (tj == null ? false : tj.IsSelected),
pd.Amount,
pd.Code,
pd.Description,
pd.Points,
pd.PackageDetailsID
};
foreach (var result in linqResult)
{
packagesSelected.Add(new PackageDetailDataModel()
{
Amount = result.Amount,
Code = result.Code,
Description = result.Description,
IsComplete = result.IsComplete,
IsMandatory = result.IsMandatory,
PackageDetailsID = result.PackageDetailsID,
PackageSelectedID = result.PackageSelectedID,
Points = result.Points,
IsActive = result.IsActive,
UserID = result.UserID,
IsSelected = result.IsSelected
});
}
SQL generated by Visualizer
SELECT
`Extent1`.`PackageDetailsID`,
`Extent2`.`IsComplete`,
`Extent2`.`IsActive`,
`Extent2`.`UserID`,
`Extent1`.`IsMandatory`,
`Extent2`.`PackageSelectedID`,
`Extent2`.`IsSelected`,
`Extent1`.`Amount`,
`Extent1`.`Code`,
`Extent1`.`Description`,
`Extent1`.`Points`
FROM `tblpackagedetails` AS `Extent1`
LEFT OUTER JOIN `tblpackageselected` AS `Extent2`
ON (`Extent1`.`PackageDetailsID` = `Extent2`.`PackageDetailsID`)
AND ((`Extent2`.`UserID` = #linq_0) AND (1 = `Extent2`.`IsActive`))
When I ran above sql in MySQL workbench I got below output (repalcing #linq_0 with userID).
My Parent Table Structure
Child Table Structure
Output I want
But the values for IsComplete, IsActive, UserID, PackageSelectedID and IsSelected null as a result condition checking in select new block assign false or 0.
If I remove null checking, I get value for first 3 rows and in fourth iteration I get below exception.
The cast to value type 'Boolean' failed because the materialized value is null. Either the result type's generic parameter or the query must use a nullable type
Please help... :(
Working code block
packagesSelected = new List<PackageDetailDataModel>();
var linqResult = from pd in entities.tblpackagedetails
join ps in entities.tblpackageselecteds
on pd.PackageDetailsID equals ps.PackageDetailsID
into tabJoin
from tj in tabJoin.Where(ps => ps.UserID == userID
&& ps.IsActive == true).DefaultIfEmpty()
select new
{
IsComplete = (bool?)tj.IsComplete,
IsActive = (bool?)tj.IsActive,
UserID = (int?)tj.UserID,
IsMandatory = pd.IsMandatory,
PackageSelectedID = (int?)tj.PackageSelectedID,
IsSelected = (bool?)tj.IsSelected,
pd.Amount,
pd.Code,
pd.Description,
pd.Points,
pd.PackageDetailsID
};
foreach (var result in linqResult)
{
packagesSelected.Add(new PackageDetailDataModel()
{
Amount = result.Amount,
Code = result.Code,
Description = result.Description,
IsComplete = (result.IsComplete ?? false),
IsMandatory = result.IsMandatory,
PackageDetailsID = result.PackageDetailsID,
PackageSelectedID = (result.PackageSelectedID ?? 0),
Points = result.Points,
IsActive = (result.IsActive ?? false),
UserID = (result.UserID ?? 0),
IsSelected = (result.IsSelected ?? false)
});
}
Thanks to 2Kay :)
When tj is null, EF consieders all properties of tj as null. It's ok, but when EF trying to materialize them into value-types it fails. So the solution is to use nullable types..
Try this query:
var linqResult = from pd in entities.tblpackagedetails
join ps in entities.tblpackageselecteds
on pd.PackageDetailsID equals ps.PackageDetailsID
into tabJoin
from tj in tabJoin.Where(ps => ps.UserID == userID
&& ps.IsActive == true).DefaultIfEmpty()
select new
{
IsComplete = (bool?) tj.IsComplete,
IsActive = (bool?) tj.IsActive,
UserID = (int?) tj.UserID,
IsMandatory = pd.IsMandatory,
PackageSelectedID = (int?) tj.PackageSelectedID,
IsSelected = (bool?) tj.IsSelected,
pd.Amount,
pd.Code,
pd.Description,
pd.Points,
pd.PackageDetailsID
};
Main Code:
DomainServiceAccountManager d = new DomainServiceAccountManager();
EntityQuery<ListBuy> q = d.GetListMemberBuyQuery();
LoadOperation<ListBuy> l = d.Load(q);
DGListBuy.ItemsSource = l.Entities;
The code:
public IQueryable<ListBuy> GetListMemberBuy()
{
var membuy =
from mem in this.ObjectContext.Members
from b in this.ObjectContext.Buys.Where(b => b.ID_member == mem.ID)
.OrderByDescending(b => b.ID)
.DefaultIfEmpty()
select new { b.ID, mem.Name, b.Money, b.Tarikh };
return membuy;
}
I get the following message:
Cannot implicitly convert type 'System.Linq.IQueryable<AnonymousType#1>' to 'System.Linq.IQueryable<AccountManager.Web.ListBuy>'. An explicit conversion exists (are you missing a cast?)
You method GetListMemberBuy actually returns an IQueryable of anonymous type instead of an IQueryable of type ListBuy. These are not identical, hence the (compile time?) error.
I can only assume that ListBuy also exists in the database, but if so, then you can remove the anonymous type.
public IQueryable<ListBuy> GetListMemberBuy()
{
var membuy =
from mem in this.ObjectContext.Members
from b in this.ObjectContext.Buys.Where(b => b.ID_member == mem.ID)
.OrderByDescending(b => b.ID)
.DefaultIfEmpty()
select new ListBuy() { ID = b.ID, Name = mem.Name, Money = b.Money, Tarikh = b.Tarikh }; // <-- new ListBuy() !!
return membuy;
}
If ListBuy does not exist in the database, then you cannot return an IQueryable. Maybe this will work.
public IEnumerable<ListBuy> GetListMemberBuy()
{
var membuy =
from mem in this.ObjectContext.Members
from b in this.ObjectContext.Buys.Where(b => b.ID_member == mem.ID)
.OrderByDescending(b => b.ID)
.DefaultIfEmpty()
select new { b.ID, mem.Name, b.Money, b.Tarikh };
return membuy
.AsEnumerable()
.Select(b => new ListBuy() {
ID = b.ID, Name = b.Name, Money = b.Money, Tarikh = b.Tarikh
});
}
All this is a bit speculation since you didn't include the ListBuy class definition in your question.
I need to build a dynamic where clause in a Linq statement with multiple joins.
.Net 3.5
Linq-To-Sql
I have these incoming parameters for the Linq statement, only the "UID" is required.
int uid = 23702; // <-- Only one Required
string courseNumber = "";
string title = "";
int? categoryId = null;
int? typeId = null;
I've been testing this out in LinqPad and while I've gotten the query to work with all Where clauses in place, the Nullable int parameters end up returning incorrect results.
Here's my Linq statement:
var ci = course_instances;
var query = courses.Join(ci,
c => c.course_id,
i => i.course_id,
(c, i) => new
{
c = c,
i = i
}).Join(user_courses,
temp => temp.i.instance_id,
uc => uc.instance_id,
(temp, uc) => new
{
temp = temp,
uc = uc
})
.Where (temp1 => (temp1.uc.uid == uid))
.Where (temp1 => (temp1.temp.c.course_number.Contains(courseNumber)))
.Where (temp1 => (temp1.temp.c.title.Contains(title)))
//.Where (temp1 => (temp1.temp.c.course_type_id == typeId))
//.Where (temp1 => (temp1.temp.c.course_category_id == categoryId))
.Select (temp1 => new CourseSearchMyCourses
{
// snipped the many properties
});
I've tried using PredicateBuilder, but it returns the error:
The type arguments for method 'System.Linq.Queryable.Where(System.Linq.IQueryable, System.Linq.Expressions.Expression>)' cannot be inferred from the usage. Try specifying the type arguments explicitly.
Here's my PredicateBuilder Linq attempt:
var conditions = PredicateBuilder.True<user_course>();
conditions = conditions.And(c => c.uid == uid);
var ci = course_instances;
var query = courses.Join(ci,
c => c.course_id,
i => i.course_id,
(c, i) => new
{
c = c,
i = i
}).Join(user_courses,
temp => temp.i.instance_id,
uc => uc.instance_id,
(temp, uc) => new
{
temp = temp,
uc = uc
})
.Where (conditions)
.Select (temp1 => new CourseSearchMyCourses
{
// snipped the many properties
});
BTW, I also tried using "System.Linq.Dynamic" using string queries, and got the error the " and " isn't recognized.
Any help is appreciated.
Thanks.
Linq predicates with nullable type variables get translated into a SQL predicate = NULL. But that is totally different than what it should be: IS NULL.
You expect to get the rows where course_type_id is empty, but the = comparison returns no results because NULL is not a value and the comparison returns UNKNOWN. I think that is the cause of your "incorrect results".
If this is your problem, a fix can be found here.
In her book Entity Framework Julie Lerman recommends using nested queries in preference to joins (scroll back a couple of pages).
In her example see populates 1 field this way, but what id you want to populate 2?
I have an example here where I would prefer to populate the Forename and Surname with the same nested query rather than 2 separate ones. I just need to know the correct syntax to do this.
public static List<RequestInfo> GetRequests(int _employeeId)
{
using (SHPContainerEntities db = new SHPContainerEntities())
{
return db.AnnualLeaveBookeds
.Where(x => x.NextApproverId == _employeeId ||
(x.ApproverId == _employeeId && x.ApprovalDate.HasValue == false))
.Select(y => new RequestInfo
{
AnnualLeaveDate = y.AnnualLeaveDate,
Forename = (
from e in db.Employees
where e.EmployeeId == y.EmployeeId
select e.Forename).FirstOrDefault(),
Surname = (
from e in db.Employees
where e.EmployeeId == y.EmployeeId
select e.Surname).FirstOrDefault(),
RequestDate = y.RequestDate,
CancelRequestDate = y.CancelRequestDate,
ApproveFlag = false,
RejectFlag = false,
Reason = string.Empty
})
.OrderBy(x => x.AnnualLeaveDate)
.ToList();
}
}
There's nothing wrong with your query, but you can write it in a way that is much simpler, without the nested queries:
public static List<RequestInfo> GetRequests(int employeeId)
{
using (SHPContainerEntities db = new SHPContainerEntities())
{
return (
from x in db.AnnualLeaveBookeds
where x.NextApproverId == employeeId ||
(x.ApproverId == employeeId && x.ApprovalDate == null)
orderby x.AnnualLeaveDate
select new RequestInfo
{
AnnualLeaveDate = x.AnnualLeaveDate,
Forename = x.Employee.Forename,
Surname = x.Employee.Surname,
RequestDate = x.RequestDate,
CancelRequestDate = x.CancelRequestDate,
ApproveFlag = false,
RejectFlag = false,
Reason = string.Empty
}).ToList();
}
}
See how I just removed your from e in db.Employees where ... select e.Forename) and simply replaced it with x.Employee.Forename. When your database contains the correct foreign key relationships, the EF designer will successfully generate a model that contain an Employee property on the AnnualLeaveBooked entity. Writing the query like this makes it much more readable.
I hope this helps.
try this
using (SHPContainerEntities db = new SHPContainerEntities())
{
return db.AnnualLeaveBookeds
.Where(x => x.NextApproverId == _employeeId ||
(x.ApproverId == _employeeId && x.ApprovalDate.HasValue == false))
.Select(y =>
{
var emp = db.Emplyees.Where(e => e.EmployeeId == y.EmployeeId);
return new RequestInfo
{
AnnualLeaveDate = y.AnnualLeaveDate,
Forename = emp.Forename,
Surname = emp.Surname,
RequestDate = y.RequestDate,
CancelRequestDate = y.CancelRequestDate,
ApproveFlag = false,
RejectFlag = false,
Reason = string.Empty
};
).OrderBy(x => x.AnnualLeaveDate).ToList();
}