I have generated below two classes using Entity Framework
public class Persons
{
public string Name { get; set; }
public int personId { get; set; }
//NAVIGATIONL PROP.
public virtual ICollection<streetLivedIn> { get; set; }
}
public class StreetLivedIn
{
public string Address1 { get; set; }
public string AddressType { get; set; }
//NAVIGATIONL PROP.
public virtual PersonId (Foriegn Key with Person)
}
There is a One-to-Many relation between Person and Street Lived In.I am trying to pull a list of persons whose AddressType, in streetlivedin table, is "Home".For this I have the below statement
var Lstpersons = db.persons()
.Include(x => x.streetlivedin)
.Where(x => x.streetlivedin.AddressType == "Home");
The above code throws an error in where clause saying it cannot convert ICollection<streetlivein> to streetlivedin class.
I would like to know how can i achieve this using Include and where.And using Persons context.(I know it can be easily achieved using streetLivedIn context..
like
var Lstpersons = db.streetlivedin()
.Include(x => x.person)
.Where(x => x.streetlivedin.AddressType == "Home");
(No join statements....Please)
You're trying to get find where streetlivedin.AddressType == "Home" but streetlivedin is a collection on the person entity. Instead, do a sub-query on streetlivedin, for example:
var Lstpersons = db.persons()
.Include(x => x.streetlivedin)
.Where(x => x.streetlivedin.Any(y=>y.AddressType == "Home"));
To get all the people with only their home address, you'd want a query something like this.
from person in db.persons()
join address in db.streetlivedin() on person.personId equals address.PersonId
where address.AddressType == "Home"
select new { Person = person, HomeAddress = address }
Of course, since that's an inner join, any person with more than one Home address would show up more than once in the results.
As an aside, the mixed capitalization would drive me nuts if I had to work with that codebase. You don't have to follow the C# coding conventions, but if you're going to pick your own convention at least make it consistent.
int id=1;
var Lstpersons=(from s in db.streetlivedins where s.AddressType == "Home" && s.PersonId ==id select s).ToList();
If you don't want specific user address
var Lstpersons=(from s in db.streetlivedins where s.AddressType == "Home" select s).ToList();
If you want persons
var Lstpersons=(from p in db.persons let st =p.streetlivedins from s in st where s.AddressType == "Home" select p).ToList();
Related
Hi good day I am new with Entity Framework. I just wanna to know if there is a way I could improve my implementation. Here are the codes.
public async Task<List<Record>> GetRecordsByBatchId(string batchId, string source)
{
List<string> idList = new List<string>();
//[1] Get all parent ID from table 1 with a filter of source and batchId
var parentIds= await _context.Set<FirstTable>()
.Where(a => a.IsActive
&& a.BatchId.Equals(batchId)
&& a.Source.Equals(source)).Select(b => b.ParentId).ToListAsync();
if (parentIds.Count() == 0)
{
return new List<Record>();
}
//[2] Query idNumber of each parentId from [1] to SecondTable
List<long> idNumber = await _context.Set<SecondTable>()
.Where(a => parentIds.Contains(a.Id))
.Select(b => b.IdNumber).ToListAsync();
//[3] Query Record/s that contains idNumber from previous query [2]. it is possible that 1 or
//more records has same idNumber
List<Risk> recordByIdNumber = await _context.Set<SecondTable>()
.Where(a => idNumber.Contains(a.IdNumber)).ToListAsync();
//[4] In this part I just want to group the records in [3] by Id number and sort each group
//by its endorsementNumber in descending order and return the record with highest endorsement
//number for each group
return (from record in recordByIdNumber
group record by record.IdNumber into g
orderby g.Key
select g.OrderByDescending(risk =>risk.EndorsementNumber).FirstOrDefault()).ToList();
}
}
The model for the FirstTable
public class FirstTable
{
public Guid? ParentId{ get; set; }
public string BatchId { get; set; }
public string Source { get; set; }
public bool IsActive { get; set; }
}
The model for the SecondTable
public class SecondTable
{
public Guid Id{ get; set; }
public int EndorsementNumber { get; set; }
public long IdNumber { get; set; }
}
Note: I just include the necessary properties in the model.
This approach is working as expected. I just wanna know if there is a possibility that these queries could be optimized that there is only 1 query for the SecondTable table.
Any help would be greatly appreciated, thanks in advance.
Yes, queries 1-3 can and should be combined. In order to do that you need, to have navigation properties in your model. It seems that there is one-to-many relationship between FirstTable and SecondTable. Let's use Customer and Order instead.
class Customer {
int CustomerId
string BatchId
ICollection<Order> Orders
}
class Order {
int OrderId
int CustomerId
Customer Customer
Risk Risk
}
in which case you just write third query as
List<Risk> = await _context.Orders.Where(o => o.Customer.BatchId == batchId)
.Select(o => o.Risk).ToListAsync();
Obviously, I am only guessing the structure and the relationship. But hopefully, this can get you started. For me Contains() is "code smell". There is a high chance that there will be large list out of your first query, and contains() will produce a huge IN clause in the database, that can easily crash the system
var parentIds = _context.Set<FirstTable>()
.Where(a => a.IsActive
&& a.BatchId.Equals(batchId)
&& a.Source.Equals(source)).Select(b => new { b.parentId });
var risks = await (from s in _context.Set<SecondTable>()
join p in parentIds on s.Id equals p.parentId
join r in _context.Set<SecondTable>() on s.IdNumber equals r.IdNumber
select r).GroupBy(r=>r.IdNumber)
.Select(r=> r.OrderByDescending(risk =>risk.EndorsementNumber).FirstOrDefault())
.ToArrayAsync();
return risks;
You can have 1 query instead of 3. It will perform better as the number of the rows from the first query grows.
EDIT: As #SvyatoslavDanyliv mentioned in the comments, group-take operations may not work depending on the version of the EF and the provider you use. You may need to separate the query and the group by operation like below :
var result = await (from s in _context.Set<SecondTable>()
join p in parentIds on s.Id equals p.parentId
join r in _context.Set<SecondTable>() on s.IdNumber equals r.IdNumber
select r).ToArrayAsync();
var risks = result.GroupBy(r=>r.IdNumber)
.Select(r=> r.OrderByDescending(
risk =>risk.EndorsementNumber).FirstOrDefault())
.ToArray();
return risks;
I have 3 tables: Person, PersonFriend, PersonGroup.
Using LINQ, i want to join the 3 tables, filter using a dynamically generated where clause, and select custom columns with flattened rows (flattened one-to-many relationship table columns).
Pseudo-SQL design:
CREATE TABLE Person (int id, varchar socialclass, date createddate);
CREATE TABLE Person_Friend (int id, id personid references person.id, id friendpersonid references person.id, varchar friendtype);
CREATE TABLE Person_Group (int id, int memberid references person.id, varchar membershiplevel);
Entities:
public class Person
{
public int Id { get; set; }
public string SocialClass { get; set; }
public DateTime? CreatedDate { get; set; }
public ICollection<PersonFriend> Friend { get; set; }
public ICollection<PersonGroup> Group { get; set; }
}
public class PersonFriend
{
public int Id { get; set; }
public int PersonId { get; set; }
public int FriendPersonId { get; set; }
public string FriendType { get; set; }
}
public class PersonGroup
{
public int Id { get; set; }
public int MemberId { get; set; }
public string MembershipLevel { get; set; }
}
query syntax LINQ:
var queryResult = from person in _context.Person
join friend in _context.PersonFriend on person.Id equals friend.FriendPersonId
join group in _context.PersonGroup on person.Id equals group.MemberId
where (friend.PersonId == 1 && friend.FriendType == "type1") || (friend.PersonId == 3 && friend.FriendType == "type2") || ...
select new { person.Id, person.SocialClass, person.CreatedDate, friend.FriendPersonId, friend.FriendType, group.Id, group.MembershipLevel };
Notice the where clause; Given a list of { PersonId, FriendType } object, I want to build the where clause like above.
Since I could not figure building a dynamic where clause for a query syntax LINQ,
I tried converting it to the Method syntax LINQ statement so i can leverage the PredicateBuilder (http://www.albahari.com/nutshell/predicatebuilder.aspx) but I run into the problem during Selecting one-to-many things into a flattened object.
var methodResult = _context.Person
.Include(x => x.Friend)
.Include(x => x.Group)
.Select(person => new { person.Id, person.SocialClass, person.CreatedDate, person.friend.FriendPersonId, person.friend.FriendType, person.group.Id, person.group.MembershipLevel });
notice that the above Select is not possible because friend is a ICollection.
I also tried using the above query syntax LINQ statement without the where clause, making it return a object instead of an annonymous object, and then calling the method .Where() with the predicate builder. But the built expression runs into LINQ => Entity Framework SQL conversion error and executes the where in the application, not in DB.
var queryResultWithoutWhere = from person in _context.Person
join friend in _context.PersonFriend on person.Id equals friend.FriendPersonId
join group in _context.PersonGroup on person.Id equals group.MemberId
select new SelectedObject { PersonId = person.Id, SocialClass = person.SocialClass, CreatedDate = person.CreatedDate, FriendId = friend.FriendPersonId, FriendType = friend.FriendType, GroupId = group.Id, MembershipLevel = group.MembershipLevel };
var predicate = PredicateBuilder.New<SelectedObject>(false);
foreach (var searchObject in searchRequestObjects)
{
predicate.Or(p => p.FriendPersonId == searchObject.FriendPersonId && p.FriendType == searchObject.FriendType);
}
var result = queryResultWithoutWhere.Where(predicate).ToList();
I feel like I tried everything I could, and I cannot seem to generate this SQL. Last resort would be writing a raw SQL string and then executing it, but I really would like to get this working with Entity Framework.
How would I accomplish creating a dynamic where clause, select into a custom flattened object, and have entity framework generate the SQL?
You can use SelectMany to flatten the collections:
var methodResult = Persons
.Include(x => x.Friend)
.Include(x => x.Group)
.SelectMany(person =>
person.Friend.SelectMany(friend =>
person.Group.Select(group =>
new {
person.Id,
person.SocialClass,
person.CreatedDate,
friend.FriendPersonId,
friend.FriendType,
GroupId = group.Id,
group.MembershipLevel
}
)
)
);
I'm having some problem with my linqToEntities query. The Product is missing in the query result. Is there any way to return the ProductQuantity with the Product property correctly with a linqToEntities expression?
public class ProductQuantity
{
public string Id { get; set; }
public string SomeProperty { get; set; }
public Product Product { get; set; }
public Guid ProductId { get; set; }
}
public class Product
{
public Guid Id { get; set; }
public string SomeProperty { get; set; }
//...
}
// MyId is the ProductId I need
// The following will return all productQuantity detail but the Product property will be null
var result = myEntities.ProductQuantities.Include(x => x.Product).Where(x => x.ProductId == MyId)
// The following will work but I want to avoid refilling the object like this :
var result = myEntities.ProductQuantities.Include(x => x.Product).Where(x => x.ProductId == MyId)
.Select(y => new ProductQuantity{ SomeProperty = y.SomeProperty, Product = y.Product});
What is the proper way to do this with linq to entities? Why the product is not just simply returned with the query ?
Thanks
EDIT 1
Look like my problem is releated to .Include() when using more than one include.
Just add a Category to ProductQuantity in the preceding example :
//This will return the product but not the category
var result = myEntities.ProductQuantities.Include(x => x.Product).Include(x=> x.Category).Single(x => x.ProductId == MyId)
//This will return the category but not the product
var result = myEntities.ProductQuantities.Include(x => x.Category).Include(x=> x.Product).Single(x => x.ProductId == MyId)
Why only one include can be used and only the first one is working??????? (a saw tons of similar example on the net?)
Any help?
Seems like there is a problem when the same entity is used in any other include. (ex: Product.Unit and Product.AlternateUnit cannot be retreived at the same time if the same entity is used ie:unit) I dont really understand why but I use separate query to fetch the data that cannot be retrieved by the include.
I have the following model, representing a self-referential many-to-many relationship between Person and "Assistant" (which is just another Person):
public class Person
{
public int Id { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public virtual ICollection<Person> Assistants { get; set; }
public virtual ICollection<Person> AssistantTo { get; set;
}
But I'm having trouble wrapping my mind around how to query for a specific assistant efficiently with LINQ. I know I can do something like this:
public Person GetAssistant(int assistedPersonId, int assistantId)
{
var assistedPerson = _context.People.Where(p => p.Id == assistedPersonId)
.Include(a => a.Assistants)
.FirstOrDefault();
return assistedPerson.Assistants.FirstOrDefault(a => a.Id == assistantId);
}
How would I achieve that with one LINQ call? In pseudo-code, I'm looking for something like:
public Person GetAssistant(int assistedPersonId, int assistantId)
{
return = _context.People.Where(
PERSONID == assistedPersonId AND
PERSON HAS AN ASSISTANT WITH assistantId)
;
}
Since an assistant is also a person, we can load it directly without having to get it via the AssistantTo row.
The query simply becomes:
_context.People.FirstOrDefault(p => p.Id == assistantId);
However, since we're also including business logic (that we want to make sure this assistant is actually an assistant to the correct person) - we can restrict the query:
_context.People.FirstOrDefault(p => p.Id == assistantId &&
p.AssistantTo.Any(pa => pa.Id == assistedPersonId));
I'm using MVC5 EF6 and Identity 2.1.
I have two classes:
public class Incident
{
public int IncidentId {get; set;}
...//Title, Description, etc
public virtual ICollection<FollowedIncident> FollowedIncidents { get; set; }
public virtual ApplicationUser User { get; set; }
}
public class FollowedIncident
{
public int FollowedIncidentId { get; set; }
public string UserId { get; set; }
public int IncidentId { get; set; }
public virtual Incident Incident { get; set; }
public virtual ApplicationUser User { get; set; }
}
So, the users will have the ability to follow an incident. (For starters, I'm not entirely sure if I need the ICollection and public virtual relationship references, but added them just in case for the time being.)
I'm trying to create the query that will show users the results of their followed incidents. In my controller, my query starts like this (I'm using Troy Goode's paging package... i.e. listUnpaged):
IQueryable<Incident> listUnpaged = db.Incidents.OrderByDescending(d => d.IncidentDate);
Then I want to filter by followed incidents. So, I want to show incidents where userId (parameter I pass to it) is equal to UserId in FollowedIncident. I've tried like this (error about conversion to bool from IEnumerable):
listUnpaged = listUnpaged.Where(s => s.FollowedIncidents.Where(t => t.UserId == userId));
And this (no error, but doesn't filter at all):
listUnpaged = listUnpaged.Where(s => s.FollowedIncidents.All(t => t.UserId == userId));
To me, it seems it should be as simple as this:
listUnpaged = listUnpaged.Where(s => s.FollowedIncidents.UserId == userId));
But, the linq extensions don't seem to like related data child properties? (I apologize for my programming terminology as I haven't quite pieced together all the names for everything yet.)
Anyone know how to accomplish this? It seems I may not even be thinking about it correct? (...since in the past, I've always used related data to supplement or add properties to a result. This will be the first time I want to narrow results by related data.)
Thank you.
Actually you're going about getting the Incidents the wrong way.. since Incident is a navigation property of FollowedIncident you should just use
IQueryable<Incident> listUnpaged = db.FollowedIncidents
.Where(a => a.UserId == userid)
.Select(a => a.Incident)
.OrderByDescending(d => d.IncidentDate);
Another option is to use Any()
IQueryable<Incident> listUnpaged = db.Incidents
.Where(a => a.FollowedIncidents.Any(b => b.UserId == userid)
.OrderByDescending(d => d.IncidentDate);
which would be like saying
Select *
From Incidents
Where Id IN (Select IncidentId
From FollowedIncident
Where UserId = #UserId)