Using entity framework, I'm trying to get back a customer with order details but I want to filter out those Orders that are active.
Customer is our EntityObject which has a collection of Order EntityObjects. CustomerDetails is our ObjectContext.
The code below will attach all orders but I want to filter and only attach those that are active. (Order.active == true). How can I do this?
I know Include builds up a nested query statement (I can observe by using .ToTraceString().) I was hoping to attach a Where clause to this nested select statement or the Include.
Customer cust;
CustomerDetails custTable = new CustomerDetails();
cust = custTable.Customer
.Where("it.cust_id = " + id)
.Include("Order") // But we only want Order.active == true!!!
.ToList().First();
Untested, but might work?
var temp = custTable.Customer.Where("it.cust_id = " + id).Include("Order");
cust = (from t in temp
where t.Order.active == true
select t).ToList().First();
Related
But updation works with below code snippet
Department department= departmentRepository.findOne(300L);
department.setName("rajiv");
departmentRepository.saveAndFlush(department);
but then this scenario being onetone mapping it could be a case where i would end up hitting 3 queries which include 2 select queries and one one update query .
To optimize the way i update it i'm trying to use this approach which is not getting updated thought executeUpdate() returns affected row as 1 .
There is a small mistake in your query.
You have used the = operator instead you should have used the like operator
You can also take help of #NamedNativeQueries
Example
DepartmentRepository.java
#Query(nativeQuery = true)
public List<Department> update(Long id);
Department.java
#SqlResultSetMapping(name="updateResult", columns = { #ColumnResult(name = "count")})
#NamedNativeQueries({
#NamedNativeQuery(
name = "Department.update",
query = "UPDATE departmemnt SET name like 'rajiv' WHERE id = ?",
resultSetMapping = "updateResult")
})
NativeQueries works more faster than normal Hibernate Queries
Yeah may this would help , in case of spring data i found a way to make it updatable and since they insist to use #transactional and extend the functionality of jparepository and now it hits only one line of statement
#Modifying(clearAutomatically = true)
#Transactional(readOnly=false)
#Query("update Department d set d.name =:name where d.id=:id")
int update(#Param("name")String name,#Param("id")Long id);
in case if i choose to for nativeQuery
#Modifying(clearAutomatically = true)
#Transactional(readOnly=false)
#Query(value="update Department d set d.name =:name where d.id=:id",nativeQuery=true)
int update(#Param("name")String name,#Param("id")Long id);
Im trying to call a stored procedure using Entity framework.
If I go direcly to the web api method it works fine, but when calling it from breeze it causes an exception on the metadata method.
The error is :
"Could not find the CLR type for...".
Anyone know how to fix this?
I had the very same issue, but thank God I figured out a solution. Instead of using a stored procedure, you should use a view, as Breeze recognizes views as DbSet<T>, just like tables. Say you have a SQL server table that contains two tables Customers and Orders.
Customers (**CustomerId**, FirstName, LastName)
Orders (OrderId, #CustomerId, OrderDate, OrderTotal)
Now, say you want a query that returns orders by CustomerId. Usually, you would do that in a stored procedure, but as I said, you need to use a view instead. So the query will look like this in the view.
Select o.OrderId, c.CustomerId, o.OrderDate, o.OrderTotal
from dbo.Orders o inner join dbo.Customers c on c.CustomerId = o.CustomerId
Notice there is no filtering (where ...). So:
i. Create a [general] view that includes the filtering key(s) and name it, say, OrdersByCustomers
ii. Add the OrdersByCustomers view to the entity model in your VS project
iii. Add the entity to the Breeze controller, as such:
public IQueryable<OrdersByCustomers> OrdersByCustomerId(int id)
{
return _contextProvider.Context.OrdersByCustomers
.Where(r => r.CustomerId == id);
}
Notice the .Where(r => r.CustomerId == id) filter. We could do it in the data service file, but because we want the user to see only his personal data, we need to filter from the server so it only returns his data.
iv. Now, that the entity is set in the controller, you may invoke it in the data service file, as such:
var getOrdersByCustomerId = function(orderObservable, id)
{
var query = breeze.EntityQuery.from('OrdersByCustomerId')
.WithParameters({ CustomerId: id });
return manager.executeQuery(query)
.then(function(data) {
if (orderObservable) orderObservable(data.results);
}
.fail(function(e) {
logError('Retrieve Data Failed');
}
}
v. You probably know what to do next from here.
Hope it helps.
I have a statement:
var items = from e in db.Elements
join a in db.LookUp
on e.ID equals a.ElementID
where e.Something == something
select new Element
{
ID = e.ID,
LookUpID = a.ID
// some other data get populated here as well
};
As you can see, all I need is a collection of Element objects with data from both tables - Elements and LookUp. This works fine. But then I need to know the number of elements selected:
int count = items.Count();
... this call throws System.NotSupportedException:
"The entity or complex type 'Database.Element' cannot be constructed in a LINQ to Entities query."
How am I supposed to select values from multiple tables into one object in Entity Framework? Thanks for any help!
You are not allowed to create an Entity class in your projection, you have to either project to a new class or an anonymous type
select new
{
ID = e.ID,
LookUpID = a.ID
// some other data get populated here as well
};
Your code doesn't work at all. The part you think worked has never been executed. The first time you executed it was when you called Count.
As exception says you cannot construct mapped entity in projection. Projection can be made only to anonymous or non mapped types. Also it is not clear why you even need this. If your class is correctly mapped you should simply call:
var items = from e in db.Elements
where e.Something == something
select e;
If LookupID is mapped property of your Element class it will be filled. If it is not mapped property you will not be able to load it with single query to Element.
Say I have two entities with about 20 properties per entity and a Many-to-Many relationship like so:
User (Id int,Name string, .......)
Issue (Id int,Name string, .......)
IssueAssignment (UserId,RoleId)
I want to create a new Issue and assign it to a number of existing Users. If I have code like so:
foreach(var userId in existingUserIds)
{
int id = userId
var user = _db.Users.First(r => r.Id == id);
issue.AssignedUsers.add(user);
}
_db.Users.AddObject(user);
_db.SaveChanges();
I noticed it seems terrribly inefficient when I run it against my SQL Database. If I look at
the SQL Profiler it's doing the following:
SELECT TOP(1) * FROM User WHERE UserId = userId
SELECT * FROM IssueAssignment ON User.Id = userId
INSERT INTO User ....
INSERT INTO IssueAssignment
My questions are:
(a) why do (1) and (2) have to happen at all?
(b) Both (1) and (2) bring back all fields do I need to do a object projection to limit the
fields, seems like unnecessary work too.
Thanks for the help
I have some possible clues for you:
This is how EF behaves. _db.Users is actaully a query and calling First on the query means executing the query in database.
I guess you are using EFv4 with T4 template and lazy loading is turned on. T4 templates create 'clever' objects which are able to fixup their navigation properties so once you add a User to an Issue it internally triggers fixup and tries to add the Issue to the User as well. This in turns triggers lazy loading of all issues related to the user.
So the trick is using dummy objects instead of real user. You know the id and you only want to create realtion between new issue and existing user. Try this (works with EFv4+ and POCOs):
foreach(var userId in existingUserIds)
{
var user = new User { Id = userId };
var _db.Users.Attach(user); // User with this Id mustn't be already loaded
issue.AssignedUsers.Add(user);
}
context.Issues.AddObject(issue);
context.SaveChanges();
I have a table AccountSecurity which is a many-to-many table that relates Account entities and Securities. When I write the query below it returns all Securities that satisfy the where clause. However each Security instance in the list no longer has the reference to the AccountSecurity it came from. So when I do list[0].AccountSecurity it is empty. Is there anyway to include that information? I know I can rewrite the query to return AccountSecurities instead and use .Include("Security") on that, but I wonder if it can be done another way.
var list = (from acctSec in base.context.AccountSecurities
where acctSec.AccountId == accountId
select acctSec.Security).ToList();
UPDATE
Of course if I do two queries the graph gets populated properly, there has to be a way to do this in one shot.
var securities = (from acctSec in base.context.AccountSecurities
where acctSec.AccountId == accountId
select acctSec.Security).ToList();
//this query populates the AccountSecurities references within Security instances returned by query above
var xref = (from acctSec in base.context.AccountSecurities
where acctSec.AccountId == accountId
select acctSec).ToList();
var list = (from sec in base.context.Securities
.Include("AccountSecurity")
where sec.AccountSecurities.Any(as => as.AccountId == accountId)
select sec).ToList();
Try this:
var list = (from acctSec in base.context.AccountSecurities.Include("Security")
where acctSec.AccountId == accountId
select acctSec).ToList();
Then simply use the Security property as needed, and since it's read at the same time AccountSecurities is (single SQL with join), it will be very efficient.