Using EF Core code-first, and I want to find any record with a similar list of a foreign entities to the entity I already have.
public class ClownModel {
public int Id { get; set; }
public List<CarModel> Cars { get; set; }
}
public class CarModel {
public int Id { get; set; }
}
var MyClown = new ClownModel() { /*add properties*/ }
//or maybe an existing record selected from database, just some ClownModel instance
Basically, "Select all the ClownModels where they have any Cars.Id that are in my MyClown.Cars"
Assuming that ClownModel has unique CarModel Id's, you can use the following query:
Matches All Ids
var ids = MyClown.Cars.Select(c => c.Id).ToList();
var query =
from cm in ctx.ClownModel
where cm.Cars.Where(c => ids.Contains(c.Id)).Count() == ids.Count
select cm;
Matches Any Ids
var ids = MyClown.Cars.Select(c => c.Id).ToList();
var query =
from cm in ctx.ClownModel
where cm.Cars.Where(c => ids.Contains(c.Id)).Any()
select cm;
Related
I have an one-to-many relation in my entities:
public class Header
{
public Header()
{
Items = new List<Item>
}
public int Id {get; set;}
public virtual ICollection<Item> Items {get; set;}
// other properties
}
public class Item
{
public int Id {get; set;}
public virtual Header Header { get; set; }
public string Title { get; set; }
public DateTime CreationDate { get; set; }
public int Weight { get; set; }
}
I want to load Header and some of its Items, so I wrote this linq to entity query(EF6):
using(var ctx = new MyContext())
{
var result = ctx.Headers.Where(someConditions)
.AsNoTracking()
.Select(header => new {
HeaderId = header.Id,
//fetch other header properties here
LastItemCreationDate = header.Items.OrderByDescending(item => item.CreationDate)
.Select(item => item.Title)
.FirstOrDefault(),
LastItemTitle = header.Items.OrderByDescending(item => item.CreationDate)
.Select(item => item.CreationDate)
.FirstOrDefault(),
LastItemWeight = header.Items.OrderByDescending(item => item.CreationDate)
.Select(item => item.Weight)
.FirstOrDefault()
}).ToList();
}
This query generate a sql script with 3 times join Header and Item tables, is there any more efficent way to write this query to join Header and Item tables one time?
Since you are using Select, you don't need AsNoTracking since the resulting query will not load any entities. The key performance impacts in your case would be indexes in the Header table suitability for your Where clause, then also whether there is a Descending Index available on the CreationDate in the Items table.
Another improvement would be to alter the projection slightly:
var result = ctx.Headers.Where(someConditions)
.Select(header => new {
HeaderId = header.Id,
LatestItem = header.Items
.OrderByDescending(item => item.CreatedDate)
.Select(item => new
{
Title = item.Title,
CreationDate = item.CreationDate,
Weight = item.Weight
}).FirstOrDefault()
}).ToList();
This will change the resulting anonymous type structure a bit, but should result in a nicer, single join.
You will get a result.HeaderId, then a null-able result.LastestItem containing the latest item's properties. So result.LatestItem?.Title instead of result.Title.
Using EF Core 2.2.2, I have a table in my database which is used to store notes for many other tables. In other words, it's sortof like a detail table in a master-detail relationship, but with multiple master tables. Consider this simplified EF Model:
public class Person
{
public Guid PersonID { get; set; }
public string Name { set; set; }
}
public class InvoiceItem
{
public Guid InvoiceItemID { get; set; }
public Guid InvoiceID { get; set; }
public string Description { get; set; }
}
public class Invoice
{
public Guid InvoiceID { get; set; }
public int InvoiceNumber { get; set; }
public List<Item> Items { get; set; }
}
public class Notes
{
public Guid NoteID { get; set; }
public Guid NoteParentID { get; set; }
public DateTime NoteDate { get; set; }
public string Note { get; set; }
}
In this case, Notes can store Person notes or Invoice notes (or InvoiceItem notes, though let's just say that the UI doesn't support that).
I have query methods set up like this:
public IQueryable<PersonDTO> GetPersonQuery()
{
return from p in Context.People
select new PersonDTO
{
PersonID = p.PersonID,
Name = p.Name
};
}
public List<PersonDTO> GetPeople()
{
return (from p in GetPersonQuery()
return p).ToList();
}
public IQueryable<InvoiceDTO> GetInvoiceQuery()
{
return from p in Context.Invoices
select new InvoiceDTO
{
InvoiceID = p.InvoiceID,
InvoiceNumber = p.InvoiceNumber
};
}
public List<InvoiceDTO> GetInvoices()
{
return (from i in GetInvoiceQuery()
return i).ToList();
}
These all work as expected. Now, let's say I add InvoiceItems to the Invoice query, like this:
public IQueryable<InvoiceDTO> GetInvoiceQuery()
{
return from p in Context.Invoices
select new InvoiceDTO
{
InvoiceID = p.InvoiceID,
InvoiceNumber = p.InvoiceNumber,
Items = (from ii in p.Items
select new ItemDTO
{
ItemID = ii.ItemID,
Description = ii.Description
}).ToList()
};
}
That also works great, and issues just a couple queries. However, the following:
public IQueryable<InvoiceDTO> GetInvoiceQuery()
{
return from p in Context.Invoices
select new InvoiceDTO
{
InvoiceID = p.InvoiceID,
InvoiceNumber = p.InvoiceNumber,
Items = (from ii in p.Items
select new ItemDTO
{
ItemID = ii.ItemID,
Description = ii.Description
}).ToList(),
Notes = (from n in Context.Notes
where i.InvoiceID = n.NoteParentID
select new NoteDTO
{
NoteID = n.NoteID,
Note = n.Note
}).ToList(),
};
}
sends a separate query to the Note table for each Invoice row in the Invoice table. So, if there are 1,000 invoices in the Invoice table, this is sending something like 1,001 queries to the database.
It appears that the Items subquery does not have the same issue because there is an explicit relationship between Invoices and Items, whereas there isn't a specific relationship between Invoices and Notes (because not all notes are related to invoices).
Is there a way to rewrite that final query, such that it will not send a separate note query for every invoice in the table?
The problem is indeed the correlated subquery versus collection navigation property. EF Core query translator still has issues processing such subqueries, which are in fact logical collection navigation properties and should have been processed in a similar fashion.
Interestingly, simulating collection navigation property with intermediate projection (let operator in LINQ query syntax) seems to fix the issue:
var query =
from i in Context.Invoices
let i_Notes = Context.Notes.Where(n => i.InvoiceID == n.NoteParentID) // <--
select new InvoiceDTO
{
InvoiceID = i.InvoiceID,
InvoiceNumber = i.InvoiceNumber,
Items = (from ii in i.Items
select new ItemDTO
{
ItemID = ii.ItemID,
Description = ii.Description
}).ToList(),
Notes = (from n in i_Notes // <--
select new NoteDTO
{
NoteID = n.NoteID,
Note = n.Note
}).ToList(),
};
LINQ Query not populating
Model extract is as follows
public class ServiceBulletin
{
[Key]
public int Id { get; set; }
public virtual ICollection<ServiceBulletinProducts> ApplicableProducts { get; set; }
}
public class ServiceBulletinProducts
{
[Key]
public int Id { get; set; }
public int ServiceBulletinId { get; set; }
public virtual Product Product{ get; set; }
}
I'm using the following code at the moment to populate a collection
var x = from m in _dc.ServiceBulletins.Include(p => p.ApplicableProducts)
.Include(m => m.Manufacturer)
where m.DeleteStatus == DeleteStatus.Active
select m;
var x1 = new List<ServiceBulletin>();
foreach (var item in x)
{
var p = from m1 in _dc.ServiceBulletinsProducts.Include(p2=>p2.Product)
where m1.Product.DeleteStatus == DeleteStatus.Active &&
m1.ServiceBulletinId == item.Id
select m1;
var p99 = p.ToList();
item.ApplicableProducts = p99;
x1.Add(item);
};
So this is intended to have a Parent Child relationship and I’m trying to do a query which populates a collection of ServiceBulletins with a ApplicableProducts item with a fully populated collection of ServiceBulletinProducts for the ServiceBulletin with the values of the Product populated
The collection is populated but the ServiceBulletinProducts are always set to null and I can’t seem to add an Include such as .Include(p => p.ApplicableProducts.Products) to try and populate the product details – which is resulting in me iterating around the collection to populate the items.
Am I missing something to enable the population on the 1st query for the Include statement or do I need to do the query in a different way ?
Figured out the following should do the trick.
var x = from m in _dc.ServiceBulletins.Include(p => p.ApplicableProducts.Select(p2=>p2.Product))
.Include(m => m.Manufacturer)
where m.DeleteStatus == DeleteStatus.Active
select m;
I've written a LINQ query shown below :
List<Actions> actions = resourceActions.Actions.Select(s => s.ActionName).ToList();
How do I give for selecting multiple columns here ? ie I want to add columns s.ActionId and s.IsActive. I'm unable to apply it.
Make a class to represent the data you want:
public class ResourceAction
{
public int Id {get;set;}
public string Name {get; set; }
}
Select a list of those instead:
List<ResourceAction> actions = resourceActions.Actions
.Select(s => new ResourceAction() { Id = s.Id, Name = s.ActionName}).ToList();
I believe this is what your looking for. However you need to change the output to an anonymous type.
var actions = resourceActions.Actions.Select(s => new { s.ActionName, s.ActionId, s.IsActive } ).ToList();
You can use a anonymous type for this, for example
var actions = resourceActions.Actions.Select(s =>
new { Id = s.Id, Name = s.ActionName, Active = s.IsActive).ToList();
but a better way would be to create a class like
public class ActionWithId
{
public int Id { get; set; }
public string Name { get; set; }
public bool Active { get; set; }
}
List<ActionWithId> actions = resourceActions.Actions.Select(s =>
new ActionWithId() { Id = s.Id, Name = s.ActionName, Active = s.IsActive }).ToList();
I'm sure this has to have been asked before, but I couldn't find a good way to search on it.
I have a class like the following
public class Vendor
{
public int VendorId { get; set; }
public string Name { get; set; }
public int ProductCount { get; set; }
}
I have a configuration class setup like
public class VendorConfiguration : EntityTypeConfiguration<Vendor>
{
public VendorConfiguration()
{
Property(p => p.Name).IsRequired().HasMaxLength(128);
Ignore(v => v.ProductCount);
}
}
Here is the query i use to grab the vendors.
public Vendor[] GetVendors()
{
using (var db = new UbidContext())
{
var query = (from vendor in db.Vendors
select vendor);
return query.ToArray();
}
}
How could I populate ProductCount with a subquery that would look similar to
ProductCount = (from vend in db.VendorProducts
where vend.VendorId == id
select vend).Count()
Is there a way I can add that to the main query, so I'm only making 1 call to the db?
Thanks,
Andrew
I would try it this way:
public Vendor[] GetVendors()
{
using (var db = new UbidContext())
{
var query = from vendor in db.Vendors
join vp in db.VendorProducts
on vendor.VendorId equals vp.VendorId
into vendorProducts
select new
{
Vendor = vendor,
ProductCount = vendorProducts.Count()
};
foreach (var item in query)
item.Vendor.ProductCount = item.ProductCount;
return query.Select(a => a.Vendor).ToArray();
}
}
Problem is that you must project into a non-entity type (anonymous in the example above) and then copy the projected ProductCount value into the projected Vendor item by item before you return it.