This is using BreezeJS and a Breeze controller through to an EF provider. I have a couple of related Entities, lets call them Customer, which has a Navigation Property called Orders which links to a set of Order Entities for that customer.
What I'd like to display on the UI is a summary of Order Counts for a set of customers who match a partial name search. I can do this through returning all the Order objects, but they're quite large objects and I don't really want to return 100's of them when I don't have to. The inlineCount() method seems to always give the count of the top-level entity (Customer) rather than of the sub-Entities, no matter where I place it in the statement.
var predicate = breeze.Predicate.create('displayName', 'contains', partialName);
return this.entityQuery.from('Customers')
.where(predicate)
.orderBy('displayName')
.using(this.manager)
.expand('Orders')
.execute();
The documentation suggests that you can chain the expand in some way, but I have yet to find a syntax which is valid.
Ideally, I'd like to apply a where to the Orders by a property on Order called Status of say 0 (incomplete) and then give me just the count of those matching Orders. ie, return me all the Customer entities, but have a matching order count for each (rather than the whole list of Order objects and filter client-side).
Would appreciate any pointers in the right direction if it's possible to achieve. My current thinking is that I'll have to create a custom method on the server-side controller and do the work there, but before I make assumptions about what OData can support, I thought I'd check here for some confirmation.
So far, this is my best approach (maybe someone can correct me if there's a better way).
On the server, add this method:
public IQueryable<object> CustomerSummaries()
{
return Context.Customers.Select(p => new
{
Customer = p,
ActiveOrderCount = p.Orders.Count(o => o.Status == 1)
});
}
Then on the client end:
var predicate = breeze.Predicate.create('customer.displayName', 'contains', partialName);
return this.entityQuery.from('CustomerSummaries')
.where(predicate)
.using(this.manager)
.execute();
Related
I have had to move queries off the main database in order to meet requirements for complex authorization - for example a user with a given authorization role can only view data for individuals in the same institution.
I am using the Breeze .net DocCode sample for guidance, and have copied the premise for the mapping of domain models to DTOs.
get { return ForCurrentUser(Context.Orders).Select(o => new Order {
OrderID = o.OrderID,
....
OrderDetails = o.OrderDetails.Select(od => new OrderDetail
{
ProductID = od.ProductID,
UnitPrice = od.UnitPrice
...
})
The problem is that which mapped properties to .include(entity framework method)/.expand (breeze method) is now a concern of the mapping function (for example, the above code will always return the OrderDetails collection, whether I want them or not). I would like to still only eagerly load/expand properties if the javascript client generated predicate has a .expand directive for that property.
Is this at all possible, or am I stuck with manually defining different mapping functions on the server, depending on what properties I want expanded? (I am happy to use tools such as automapper if that would solve or simplify the problem)
Thank you
You will need to use the ODataQueryOptions as a parameter to your controller method. This gives you the details of the query predicates in your server method, so that you can apply them as needed rather that having them applied automatically. This will let you expand, or not, based upon the query.
See this answer and this answer to see how it works.
We have controllers that read Entities with certain criteria and return a set of view models containing the data to the view. The view uses a Kendo Grid, but I don't think that makes a particular difference.
In each case, we have a Linq Query that gets the overall collection of entity rows and then a foreach loop that creates a model from each row.
Each entity has certain look ups as follows:
those with a 1:1 relationship, e.g. Assigned to (via a foreign key to a single person)
those with a 1:many relationship e.g. copy parties (to 0:many people - there are not many of these)
counts of other relationships (e.g. the number of linked orders)
any (e.g. whether any history exists)
If we do these in the model creation, the performance is not good as the queries must be run separately for each and every row.
We have also tried using includes to eager load the related entities but once you get more than two, this starts to deteriorate too.
I have seen that compiled queries and LoadProperty may be an option and I am particularly interested in the latter.
It would be great to understand best practice in these situations, so I can direct my investigations.
Thanks,
Chris.
Edit - sample code added. However, I'm looking for best practice.
public JsonResult ReadUsersEvents([DataSourceRequest]DataSourceRequest request, Guid userID)
{
var diaryEventModels = new List<DiaryEventModel>();
var events = UnitOfWork.EventRepository.All().Where(e => e.UserID == userID);
foreach (var eventItem in events)
{
var diaryModel = new DiaryEventModel(eventItem);
diaryEventModels.Add(diaryModel);
}
var result = diaryEventModels.ToDataSourceResult(request);
return Json(result, JsonRequestBehavior.AllowGet);
}
public DiaryEventModel(Event eventItem) {
// Regular property from Entity examples - no issue here as data retrived simply in original query
ID = eventItem.ID;
Start = eventItem.StartDateTime;
End = eventItem.EndDateTime;
EventDescription = eventItem.Description;
// One to one looked up Property example
eventModel.Creator = eventItem.Location.FullName;
// Calculation example based on 0 to many looked up properties, also use .Any in some cases
// This is a simplified example
eventModel.AttendeeCount = eventItem.EventAttendees.Count();
// 0 to Many looked up properties
EventAttendees = eventItem.EventAttendees.Select(e => new SelectListItem
{
Text = e.Person.FullName,
Value = e.Person.ID.ToString()
}).ToList();
}
I have a Users table of 76 users and UserGroups table.
Using MVC, OData, a generic repository and EF, I am trying to optimize data retrieval when filtering based on the user group:
/api/Users?$filter=USERGROUPS/any(usergroup: usergroup/ID eq 'Group1')
On the client side, I get the right number of users - 71 (as OData is filtering based on the result), however I want to limit the number of records being returned form the actual query - ie. I do not want to return all records then filter (not optimal for very large data sets).
My API controller method is as follows:
[Queryable(AllowedQueryOptions = AllowedQueryOptions.All)]
public IQueryable<USER> Get()
{
var unitOfWork = new ATMS.Repository.UnitOfWork(_dbContext);
var users = unitOfWork.Repository<USER>()
.Query()
.Include(u => u.USERGROUPS)
.Get()
.OrderBy(order => order.USERNAME);
unitOfWork.Save(); // includes Dispose()
return users.AsQueryable();
}
I read in this post that:
Entity framework takes care of building dynamic query based on the
request.
However, using a SQL Server profiler, the query executed is requesting all the records, rather than a filtered query.
Adding a .Take() to the query does not accomplish the desired result, as we also need the actual number of records returned for paging purposes.
I was thinking of using the grabbing some properties through ODataQueryOptions, but that doesn't seem quite right either.
Is my implementation of Unit of Work and Repository incorrect, in relation to what I am trying to accomplish, and if so, how can this be corrected?
Simple - Just set the Page size for the Queryable atrribute [Queryable(PageSize=10)]
http://www.asp.net/web-api/overview/odata-support-in-aspnet-web-api/supporting-odata-query-options#server-paging
If You'd tell the EF where to apply the options, it would work.
Like this :
//[Queryable(AllowedQueryOptions = AllowedQueryOptions.All)]
public IQueryable<USER> Get(ODataQueryOptions<USER> options)
{
var users = options.ApplyTo(_dbContext.Set<USER>()
.Query()
.Include(u => u.USERGROUPS)
.Get()
.OrderBy(order => order.USERNAME));
return users;
}
Your code didn't work, because it tried to apply the options onto the last line "users.AsQueryable()", so what actually happened, is that EF pull the FULL dataset, and then applied the query onto the last line (that being a in memory collection). And that's why You didn't see that "filter" not being passed to the SQL.
The mechanics are such, that EF tries to apply the Query, to the IQueryable collection that it finds in the code (there's still a question how does it find the correct line).
I'm still trying to get my feet on the ground with Silverlight and RIA Services, and of course starting with some of the more "fun" stuff like grids and intelligent paging. I can connect to RIA Services (using a home-grown ORM, not L2S or EF), get data on the grid, and connect to a DataPager. The domain service is working well with the home-grown ORM, at least for queries. (Still working on full CRUD.) However, there are still problems:
To support the user application, I need user-controlled sorting and filtering, in addition to smart paging (only run the query for the rows needed to display) and grouping.
So far, I've seen nothing in the DataGrid or DataPager to externalize these capabilities so that filtering, sorting, and paging parameters can be passed to the server to build the appropriate query.
The datasets are potentially quite large; my table I've chosen for prototyping work can have up to 35,000 entries at some customers, and I'm sure there are other tables far larger that I will have to deal with at some point. So the "smart paging" aspect is essential.
Ideas, suggestions, guidance, and nerf bricks are all welcome.
OK, I've spent a few days in the weeds with this one, and I think I've got a handle on it.
First, an important piece of magic. For paging to work properly, the pager has to know the total item count, no matter how many items were returned by the current query. If the query returns everything, the item count is obviously the number of items returned. For smart paging, the item count is still the total of available items, although the query returns only what gets displayed. With filtering, even the total of available items changes every time the filter changes.
The Silverlight Datapager control has a property called ItemCount. It is readonly and cannot be databound in XAML, or set directly in code. However, if the user control containing the pager has a DataContext that implements IPagedCollectionView, then the data context object must implement an ItemCount property with PropertyChanged notification, and the DataPager seems to pick this up automagically.
Second, I highly recommend Brad Abrams' excellent series of blog posts on RIA Services, especially this one on ViewModel. It contains most of what you need to make paging and filtering work, although it's missing the critical piece on managing the item count. His downloadable sample also contains a very good basic framework for implementing ModelViewViewModel (MVVM). Thank you, Brad!
So here's how to make the item count work. (This code refers to a custom ORM, while Brad's code uses Entity Framework; between the two you can figure you what you need in your environment.)
First, your ORM needs to support getting record counts, with and without your filter. Here's my domain service code that makes the counts available to RIA Services:
[Invoke]
public int GetExamCount()
{
return Context.Exams.Count();
}
[Invoke]
public int GetFilteredExamCount(string descriptionFilter)
{
return Context.Exams.GetFilteredCount(descriptionFilter);
}
Note the [Invoke] attribute. You need this for any DomainService method that doesn't return an Entity or an Entity collection.
Now for the ViewModel code. You need an ItemCount, of course. (This is from Brad's example.)
int itemCount;
public int ItemCount
{
get { return itemCount; }
set
{
if (itemCount != value)
{
itemCount = value;
RaisePropertyChanged(ItemCountChangedEventArgs);
}
}
}
Your LoadData method will run the query to get the current set of rows for display in the DataGrid. (This doesn't implement custom sorting yet, but that's an easy addition.)
EntityQuery<ExamEntity> query =
DomainContext.GetPagedExamsQuery(PageSize * PageIndex, PageSize, DescriptionFilterText);
DomainContext.Load(query, OnExamsLoaded, null);
The callback method then runs the query to get the counts. If no filter is being used, we get the count for all rows; if there's a filter, then we get the count for filtered rows.
private void OnExamsLoaded(LoadOperation<ExamEntity> loadOperation)
{
if (loadOperation.Error != null)
{
//raise an event...
ErrorRaising(this, new ErrorEventArgs(loadOperation.Error));
}
else
{
Exams.MoveCurrentToFirst();
if (string.IsNullOrEmpty(DescriptionFilterText))
{
DomainContext.GetExamCount(OnCountCompleted, null);
}
else
{
DomainContext.GetFilteredExamCount(DescriptionFilterText, OnCountCompleted, null);
}
IsLoading = false;
}
}
There's also a callback method for counts:
void OnCountCompleted(InvokeOperation<int> op)
{
ItemCount = op.Value;
TotalItemCount = op.Value;
}
With the ItemCount set, the Datapager control picks it up, and we have paging with filtering and a smart query that returns only the records to be displayed!
LINQ makes the query easy with .Skip() and .Take(). Doing this with raw ADO.NET is harder. I learned how to do this by taking apart a LINQ-generated query.
SELECT * FROM
(select ROW_NUMBER() OVER (ORDER BY Description) as rownum, *
FROM Exams as T0 WHERE T0.Description LIKE #description ) as T1
WHERE T1.rownum between #first AND #last ORDER BY rownum
The clause "select ROW_NUMBER() OVER (ORDER BY Description) as rownum" is the interesting part, because not many people use "OVER" yet. This clause sorts the table on Description before assigning row numbers, and the filter is also applied before row numbers are assigned. This allows the outer SELECT to filter on row numbers, after sorting and filtering.
So there it is, smart paging with filtering, in RIA Services and Silverlight!
Here's the quick and dirty solution (that I went for):
Just move your DomainDataSource to your ViewModel! Done!
May not exactly be great for testability and probably some other limitations I haven't discovered yet, but personally I don't care about that until something better comes along.
Inside your ViewModel just instantiate the data source :
// Feedback DataSource
_dsFeedback = new DomainDataSource();
_dsFeedback.DomainContext = _razorSiteDomainContext;
_dsFeedback.QueryName = "GetOrderedFeedbacks";
_dsFeedback.PageSize = 10;
_dsFeedback.Load();
and provide a bindable property :
private DomainDataSource _dsFeedback { get; set; }
public DomainDataSource Feedback
{
get
{
return _dsFeedback;
}
}
And add your DataPager to your XAML:
<data:DataPager Grid.Row="1"
HorizontalAlignment="Stretch"
Source="{Binding Feedback.Data}"
Margin="0,0,0,5" />
<data:DataGrid ItemsSource="{Binding Feedback.Data}">
PS. Thanks to 'Francois' from the above linked page. I didn't even realize I could take the DomainDataSource out of the XAML until I saw your comment!
This is an interesting article from May 2010 about the possible future support for this type of feature in the framework.
http://www.riaservicesblog.net/Blog/post/WCF-RIA-Services-Speculation-EntityCollectionView.aspx
Ok, so let me explain a little of what I am trying to do.
I have a table called WebsitePage that contains all of the pages on my site with some information about them. Then, I have a Customer table for all of my customers. Then I have another table called CustomerWebsitePage that stores customer values for some of the columns in the WebsitePage table.
So, using the entity framework, I imported these three tables. What I want to be able to do is return a strongly typed WebsitePage list that has any values from CustomerWebsitePage if there are any values for it. So, for example, say one of my customers added a CustomerWebsitePageName for one of my website pages. I want to return a list of WebsitePages that contains the CustomerWebsitePageName instead of the WebsitePage Name in that case. But the original WebsitePage Name for everything else since it wasn't overridden.
The kicker here is that my WebsitePage table has a foreign key to itself for a Parent/Child relationship. So, I also want to return the child WebsitePages at the same time. I tried using a function import to get what I wanted, but then of course I lost the ChildPages.
I have tried just about everything to get what I want using the Entity framework and LINQ. But so far almost everything I try ends up with an exception being thrown. Here are a few:
The EntityCollection has already been initialized
The entity or complex type 'MyEntityModel.WebsitePage' cannot be constructed in a LINQ to Entities query.
I have one idea of how I can get around all this, and that would be to duplicate the ParentPageID into my WebsitePage table, but this really seems to violate a lot of principles and I really just don't want to add the maintenance headache related to this.
Anyone have any ideas how to accomplish this type of thing?
A simple DB diagram. http://images.tehone.com/screenshots/2009-08-17_013009.png
The object that you need to return is a CustomerWebsitePage and not a WebsitePage. The reason is that whatever object you return must know about the customer since the property will need it to determine which field (CustomerPage or WebsitePage) to use.
Considering that, you can have a function CustomerWebsitePage.GetAllPagesForCustomer(Customer c) that would return an enumeration of pages. However, to achieve the functionality you are looking for, you must implement some read-through properties in the CustomerWebsitePage. Let's take the example of Name. Here would be how to implement it in CustomerWebsitePage:
public string Name
{
get{ if( String.IsNullOrEmpty(CustomerWebsitePageName) )
return WebsitePage.Name;
return CustomerWebsitePageName; }
}
For the Children pages, you could have a property:
public IEnumerable<CustomerWebPage> Children
{
get
{
return WebsitePage.Children.Select( it => it.Customer.CustomerID == this.CustomerID ); }
}
Note that with this setup you couldn't run EF Linq queries on these new fields (because they exist only in the objects themselves, not in the database mapping). You can pepper the code with Load() if you want to seamlessly load all the children, but it will cost you in performance. To ensure that all the children are loaded, try the following loading function:
IEnumerable<CusomterWebPage> GetAllPagesForCustomer(Customer c)
{
return Context.CustomerWebPageSet.Include("WebsitePage").Where( it => it.Customer.CustomerID == c.CustomerID );
}