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.
Related
I'm developing a client app that uses breezejs and Entity Framework 6 on the back end. I've got a statement like this:
var country = 'Mexico';
var customers = EntityQuery.from('customers')
.where('country', '==', country)
.expand('order')
I want to use There may be hundreds of orders that each customer has made. For the purposes of performance, I only want to retrieve the latest order for each customer. This will be based on the created date for the order. In SQL, I could write something like this:
SELECT c.customerId, companyName, ContactName, City, Country, max(o.OrderDate) as LatestOrder FROM Customers c
inner join Orders o on c.CustomerID = o.CustomerID
group by c.customerId, companyName, ContactName, City, Country
If this was run against the northwind database, only the most recent order row is returned for each customer.
How can I write a similar query in breeze, so that it runs on the server side and therefore returns less data to the client. I know I could handle this all on the client but writing some javascript in a querysucceeded method that could be run by the client - but that's not the goal here.
thanks
For a case like this, you should create a special endpoint method that will perform your query.
Then you can use an Entity Framework query to do what you want, using the LINQ syntax.
Here are two Web API examples:
[HttpGet]
public IQueryable<Object> CustomersLatestOrderEntities()
{
// IQueryable<Object> containing Customer and Order entity
var entities = ContextProvider.Context.Customers.Select(c => new { Customer = c, LatestOrder = c.Orders.OrderByDescending(o => o.OrderDate).FirstOrDefault() });
return entities;
}
[HttpGet]
public IQueryable<Object> CustomersLatestOrderProjections()
{
// IQueryable<Object> containing Customer and Order entity
var entities = ContextProvider.Context.Customers.Select(c => new { Customer = c, LatestOrder = c.Orders.OrderByDescending(o => o.OrderDate).FirstOrDefault() });
// IQueryable<Object> containing just data fields, no entities
var projections = entities.Select(e => new { e.Customer.CustomerID, e.Customer.ContactName, e.LatestOrder.OrderDate });
return projections;
}
Note that you have a choice here. You can return actual entities, or you can return just some data fields. Which is right for you depends upon how you are going to use them on the client. If they are just for display in a
non-editable list, you can just return the plain data (CustomersLatestOrderProjections above). If they can potentially
be edited, then return the object containing the entities (CustomersLatestOrderEntities). Breeze will merge the entities
into its cache, even though they are contained inside this anonymous object.
Either way, because it returns IQueryable, you can use the Breeze filtering syntax from the client to further qualify the query.
var projectionQuery = breeze.EntityQuery.from("CustomersLatestOrderProjections")
.skip(20)
.take(10);
var entityQuery = breeze.EntityQuery.from("CustomersLatestOrderEntities")
.where('customer.countryName', 'startsWith', 'C');
.take(10);
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.
I've set up a many-to-many association between two tables based on a third table that just holds a pair of key values. Now I'd like to do a query that groups the right tables key values by the lefts without needing other data.
LeftTable { LeftID, LeftField1, LeftField2 }
JoinTable { LeftID, RightID}
RightTable { RightID, RightField1, RightField2 }
Is there any way to essentially just query the JoinTable and get all the 'RightIDs' grouped by the 'LeftIDs' without the SQL trying to fetch the fields from either side?
The JoinTable is not an entity in its own right in the model, but is mapped to the association.
I've experimented a bit with both using ObjectQuery and EntityCommand (ESQL) and both seem to still load in the other fields by joining to RightTable which I don't need.
My ESQL looks something like:
SELECT lt.LeftID, (SELECT rt.RightID
FROM NAVIGATE(lt, MyModel.LeftToRightAssoc, RightTable) as rt)
FROM MyEntities.LeftTable as lt;
but the generated SQL is still fetching in RightField1 and RightField2.
Surely there must be a simpler way to do this?
Assuming that your class Left has a navigation property Rights (a collection of Right entities) you could try this:
var list = context.Lefts.Select(l => new
{
LeftId = l.LeftId,
RightIds = l.Rights.Select(r => r.RightId)
});
foreach (var item in list)
{
Console.WriteLine("LeftId = {0}", item.LeftId);
foreach (var rightId in item.RightIds)
{
Console.WriteLine("RightId = {0}", rightId);
}
}
You would get a collection of anonymous type objects where each element has the LeftId and a collection of corresponding RightIds. This query should not touch the other fields like RightField1, etc. Instead of an anonymous type you could also create your own custom type and then project into this type in the query above.
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.