I am using dynamic linq to make a generic class for processing a generic JqGrid from MVC all works fine (searching, pagination etc) except for sorting on code properties. Sorting works fine when I am hitting the DB to sort the data, but as soon as it is a property I have made the sorting does not work eg
public partial class tblStockOrder
{
public string approved
{
get
{
return approved_id == null ? "" : "Approved";
}
}
}
I am running the following Dynamic Linq
items = items
.OrderBy(string.Format("{0} {1}", sidx, sord))
.Skip(pageIndex * pageSize)
.Take(pageSize);
Where sidx etc are strings passed in by jquery.
So basically what is the best solution for handling a case where some properties will be from the db while others will be code properties (not sure of the correct naming). I can handle all this in code using reflection but would obviously like the DB to handle as much of the searching / sorting as possible without pulling in thousands of records and sorting through them in code using reflection.
Computed class will of course not work, as you're trying to create record which is part in memory, part in database.
You can, however, compute the same on database by specifying the function in linq query, example:
items = items
.OrderBy(x=> x.approved_id != null )
.Skip(pageIndex * pageSize)
.Take(pageSize);
Related
I have a DbSet<Items> collection.
The primary key is a Guid. I don't want to order by this primary key. I want to order by an editable decimal property named "Order".
The code I have is very simple, and it works great until the user puts a "$top" parameter into the request:
public class ItemsController : ApiController
{
protected DbContext ctx = // ...
// GET api/documents
[EnableQuery()]
public IQueryable<Item> Get()
{
return ctx.Items.OrderBy(o => o.Order).AsQueryable();
}
When the user puts "$top" into the query string, the order gets all messed up (it presumably forces the ordering to be done by the primary key, for consistent paging results -- however, in my situation, this is having the opposite effect, it's preventing me from having consistent paging results).
I've tried moving .AsQueryable() to be earlier in the query (before the .OrderBy(...) clause), I've tried it without the .AsQueryable(), I've tried it with two AsQueryables, etc.
There are going to be a lot of items in this table, so it needs to be done via an IQueryable (enumerating all of the items on the web server via IEnumerable is not an option here).
The only thing that has worked so far is passing in "$orderby=Order" from the client, but I don't want to force that (seems like it will get forgotten easily).
1.) Is there anything I can do to make ordering by my Order property the default behavior here?
2.) Or failing that, is there anyway to trick WebApi / OData into thinking that a custom "$orderby=Order" clause was specified?
To override default sort order, you need to set property EnsureStableOrdering of EnableQueryAttribute to false, like describe here:
A true value indicates the original query should be modified when
necessary to guarantee a stable sort order. A false value indicates
the sort order can be considered stable without modifying the query.
Query providers that ensure a stable sort order should set this value
to false. The default value is true.
So in your code, changes the action attribute like this:
// GET api/documents
[EnableQuery(EnsureStableOrdering = false)]
public IQueryable<Item> Get()
{
return ctx.Items.OrderBy(o => o.Order).AsQueryable();
}
You can manually invoke the odata in your controller. This should create the proper sorted IQueryable and then apply the $top and any other odata like $filter and $skip. Now you don't have to return an IQueryable which was causing the problem because the actual query was being executed later in the pipeline.
public class ItemsController : ApiController
{
protected DbContext ctx = // ...
public IEnumerable<Item> Get(ODataQueryOptions<Item> odata)
{
var collection = ctx.Items.OrderBy(o => o.Order);
if (odata == null)
{
//return a default max size of 100
return collection.Take(100).ToList();
}
var results = odata.ApplyTo(collection.AsQueryable()) as List<Item>;
//still provide a max incase the $top wasn't specified.
//you could check the odata to see if $top is there or not.
return results.Take(100);
}
}
More information can be found in the WebApi documentation.
I am working on an MVC3 project whose model is designed using Code First approach. I am using EF4 for ORM and have a need where I need two thing -
1. Intercept the context.SaveChages method
2.Do my own custom update query for one specific entity type only.
I got the first part working by overriding the SaveChanges() method like -
public override int SaveChanges()
{
var modifiedItems = this.ChangeTracker.Entries().Where(e => e.State == System.Data.EntityState.Modified && e.Entity is myEntityName);
foreach (var item in modifiedItems)
{
//ToDo: Write UPDATE Sql Query here
}
return base.SaveChanges();
}
How can I write my update query?
Thanks!
This is not possible. You can only map custom stored procedures to be used instead of CUD operations (only with EDMX) generated by EF but still you will have single stored procedure call per each operation and entity instance.
I have a basic view that returns the same columns as a table (give or take 1 field)
in my DAL code, i am returning a list of MyTableObject, however in some cases, i will call the view to return the same data, but from different sources.
List<MyTableObject> tableObjects = new List<MyTableObject>();
if (case1)
tableObjects = entities.MyTableObjects.Where(criteria).ToList();
else
tableObjects = entities.MyViewObjects.Where(criteria).ToList(); // <-- This will obviously break
return tableObjects;
is there a way to Map view entities to be returned as table entities? (other than having table and view implement the same interface and return that interface) i would like to keep the return type as MyTableObject.
I came across Auto Mapper, but not sure if it would be suitable for this scenario..
Looks like i found a cool solution to this..
Initially I tried to implement interface approach and run into some casting issues (using interfaces alongside my predicate builder), and also with interfaces having to create partial classes for each entity that implement the interface..
the answer.. POCOs.
Iused Poco Template for EF, and than simply edited xxxPocoGenerator.Context.tt to return MyTable object from MyViews collection (one line).
public ObjectSet<Trade> v_Trade {
get { return _v_Trade ?? (_v_Trade = CreateObjectSet<Trade>("Trades")); }
}
nice and easy..
You can write a stored procedure (or CommandText in the model, without creating DB Object) that will simply call "Select * from View". Then create Function Import for this procedure and set the return type to MyTableObject.
I'm working on a project that groups data by a "customer id". When the user logs in, they're limited to that customer and that customer only.
I'm working with SubSonic3, and what I've got looks something like this:
public IEnumerable<Models.Foo> FindFoo(int userID, string searchText, int pageIndex, int pageSize)
{
return from item in Foo.GetPaged(pageIndex, pageSize)
where (item.Name.Contains(searchText) ||
item.Description.Contains(searchText)) &&
item.CustomerID == CurrentCustomerID()
select new Models.Foo(item);
}
What I'd like to do is abstract away the item.CustomerID line, because that's going to happen for every query, without fail, so it would be simpler (and more secure) to do it in one place and guarantee it'll happen everywhere.
So, my question is: can this be done, and if so, how?
As far as subsonic generated classes are partial you can add some interface to them... Just create you're interface with CustomerID property (for example name it ICusomerEntity) and make partial for any of generated classes that will apply this interface to them... then just use the generic subsonic methods to rerieve ICustomerEntity, not the specific class..
For example you can make generic method called GetCustomerEntity with constraint T:ICustomerEntity which will return IQueriable with a bascic query comparing CustomerId with the one of logged user..
Hope it helps...
I have an Extension method which is supposed to filter a Queryable object (IQueryable) based upon a collection of Ids....
Note that IQueryable is sourced from my database via a LinqToSql request
public static IQueryable<NewsItemSummary> WithID(this IQueryable<NewsItemSummary> qry, IQueryable<Guid> Ids)
{
return from newsItemSummary in qry
where Ids.Contains(newsItemSummary.ID)
select newsItemSummary;
}
If Ids are created from an array or list and passed in as a queryable list, it DOESNT work
For example...
GetNewsItemSummary().WithID(ids.AsQueryable<Guid>())
If Ids is composed form a LinqToSql request, it DOES work!!
This is known issue:
http://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=355026
My Ids collection cannot come from a LinqToSql request...
Note, if I change the function so that it consumes and IList rather than an IQueryable....
public static IQueryable<NewsItemSummary> WithID(this IQueryable<NewsItemSummary> qry, IList<Guid> Ids)
{
return from newsItemSummary in qry
where Ids.Contains(newsItemSummary.ID)
select newsItemSummary;
}
I now get the following exception:
Method 'Boolean Contains(System.Guid)' has no supported translation to SQL.
So... all I want to do is filter my collection of news based upon a list or array of Guids.... Ideas???
This will translate.
public static IQueryable<NewsItemSummary> WithID(
this IQueryable<NewsItemSummary> qry,
List<Guid> Ids
)
{
return from newsItemSummary in qry
where Ids.Contains(newsItemSummary.ID)
select newsItemSummary;
}
)
Translation of the Contains method against local collections was one of the last features added in the development of linq to sql for .net 3.5, so there are some cases that you would expect work that don't - such as translation of IList<T>.
Also, be aware that while LinqToSql will happily translate lists containing a vast number of items (I've seen it do over 50,000 elements), SQL Server will only accept 2,100 parameters for a single query.