I'm trying to page a data set in a WPF application.
My service method looks like this:
public ObservableCollection<MyModel> GetPageOfModels(int projectId, int numSkip, int numResults)
{
this.db.Set<MyModel>()
.Where(x => x.Project.Id == projectId)
.OrderBy(x => x.Name)
.Skip(numSkip)
.Take(numResults)
.Load();
return this.db.Set<MyModel>().Local;
}
This works great the first time it is hit. But when I move to a different page, Load() is adding the next page to the set, rather than replacing it.
If I recreate the data context before each call to GetPageOfModels it works, but I need to keep the same data context. Is there any way to achieve this?
If you must keep the context then you could detach everything before getting the next page.
foreach(var entity in db.Set<MyModel>().Local.ToList())
db.Entry(entity).State = EntityState.Detached;
Related
I have a many-to-many structure mapped to entity framework. This is a sample of what it looks like:
User UserTag Tag
------- -------- -------
IdUser(PK) IdUserTag(PK) IdTag(PK)
Name IdUser(FK) TagName
Desc IdTag(FK) Active
Now, I needed to exclude from any request of any method the viewing of Tags that were Active=false.
First, I tried doing it manually in every method, like:
public User GetById(int id)
{
var item = UserRepository.GetById(id); //This is just a repository that calls the EF context
//EF automatically maps it to the *UserTags* property
foreach(var tag in item.UserTags)
{
if(tag.Tag.Active == false)
item.UserTags.Remove(tag);
}
}
But it throws the following exception:
The relationship could not be changed because one or more of the foreign-key properties is non-nullable
So, I wanted to know if there's a way to conditionaly filter every request made to a specific table, whether it is select or a join request.
Try this in your GetById method:
var user.UserTags = dbContext.Entry(user)
.Collection(u => u.UserTags)
.Query()
.Where(ut => ut.Active == true)
.ToList();
The supplied code fails because it is attempting to remove items from the data entities not the list. If you want to pass the data entity around instead of the data model, you need to not use Remove. Something like the below (untested should work).
tags = item.UserTags.Where((ut) => ut.Active).ToList();
This line will get you a list of data entities that are active. However, you should really map all of this into a data model (see AutoMapper) and then you would not be removing items from the database.
I've two controllers one is "Upload" which deals with images uploads and other is "Page" whid deals with the creation of pages of CMS now if in my "Upload" controller I load both the models i.e 'image_m' which deals with image upload and "page_m" which deals with the pages creation I've highlighted the relevant code my problem is if I access the variables in the view
$this->data['images'] = $this->image_m->get(); sent by this I can access in foreach loop as "$images->image_title, $images->image_path" etc
But the variable sent by this line ***$this->data['get_with_images'] = $this->page_m->get_no_parents();*** as $get_with_images->page_name, $get_with_images->page_id etc produces given error
A PHP Error was encountered
Severity: Notice
Message: Trying to get property of non-object
Filename: upload/index.php
Line Number: 20
what is the difference between these two access levels one for $image & other for $get_with_images because I can only access its values as $get_with_images
class Upload extends Admin_Controller {
public function __construct() {
parent::__construct();
***$this->load->model('image_m');
$this->load->model('page_m');***
}
public function index($id = NULL) {
//var_dump($this->data['images'] = $this->image_m->get_with_images());
//$this->data['images'] = $this->image_m->get_with_images();
***$this->data['images'] = $this->image_m->get();***
$this->data['subview'] = 'admin/upload/index';
if ($id) {
$this->data['image'] = $this->image_m->get($id);
count($this->data['image']) || $this->data['errors'][] = 'Page Could not be found';
}
$id == NULL || $this->data['image'] = $this->image_m->get($id);
/*this calls the page_m model function to load all the pages from pages table*/
***$this->data['get_with_images'] = $this->page_m->get_no_parents();***
You are not posting all your code so its hard to tell but is it because you used $this-> in the controller, but you haven't done the same thing in the view?
In this case i would recommend not using $this-> because its not necessary. Also its much better to check for errors etc when you call the model so do something like
if ( ! $data['images'] = $this->image_m->get($id) ) {
// Failure -- show an appropriate view for not getting any images
// am showing $data in case you have other values that are getting passed
$this->load->view( 'sadview', $data ); }
else {
// Success -- show a view to display images
$this->load->view( 'awesomeview', $data ); }
so we are saying if nothing came back - the ! is a negative - then show the failure view. Else $data['images'] came back, and it will be passed to the view. note i have not had to use $this-> for anything and it won't be needed in the view.
Would also suggest using separate methods - have one method to show all images and a separate method like returnimage($id) to show an image based on a specific validated $id.
====== Edit
You can access as many models as you want and pass that data to the View. You have a different issue - the problem is that you are waiting until the View to find out - and then it makes it more difficult to figure out what is wrong.
Look at this page and make sure you understand the differences between query results
http://ellislab.com/codeigniter/user-guide/database/results.html
When you have problems like this the first thing to do is make a simple view, and echo out directly from the model method that is giving you problems. Its probably something very simple but you are having to look through so much code that its difficult to discover.
The next thing is that for every method you write, you need to ask yourself 'what if it doesn't return anything?' and then deal with those conditions as part of your code. Always validate any input coming in to your methods (even links) and always have fallbacks for any method connecting to a database.
On your view do a var_dump($get_with_images) The error being given is that you are trying to use/access $get_with_images as an object but it is not an object.
or better yet on your controller do a
echo '<pre>';
var_dump($this->page_m->get_no_parents());
exit();
maybe your model is not returning anything or is returning something but the data is not an object , maybe an array of object that you still need to loop through in some cases.
I am having some difficulty with ordering an observable collection in my ViewModel.
Here is my situation:
In my view model, I have the following list:
public List<TicketModel> Tickets
{
get { return _Tickets.Value; }
set
{
{
this.RaiseAndSetIfChanged(c => c.Tickets, value);
}
}
}
private ObservableAsPropertyHelper<List<TicketModel>> _Tickets;
This list is populated using a ReactiveAsyncCommand:
LoadTickets.RegisterAsyncFunction(x => loadTickets())
.ToProperty(this, x => x.Tickets);
All works so far.
I have another command, SortByCommand which gets called whenever the user wants to sort a collection. The command looks like this:
SortByCommand = new ReactiveCommand(this.WhenAny(c => c.Tickets, ((tickets) => tickets.Value != null && tickets.Value.Count > 0)));
SortByCommand.Subscribe(c => sortTickets((SortByModel)c));
The command also calls a function that orders the collection using an order by clause:
private void sortTickets(SortByModel model)
{
Tickets = Tickets.OrderBy(model.Selector).ToList();
}
Whenever the sortTickets function is called, there is an exception thrown which says:
Unable to cast object of type 'ReactiveUI.ObservableAsPropertyHelper`1[System.Collections.Generic.List`1[Bugmine.Modules.MyPage.Models.TicketModel]]' to type 'System.Collections.Generic.List`1[Bugmine.Modules.MyPage.Models.TicketModel]'.
I have several questions:
1) Why can't I set directly the Tickets model? Do I need to first convert the result of the OrderBy to some sort of observable collection?
2) Is there a better way of doing this?
EDIT: Clarification
The approach I am taking right now is:
The Tickets collection gets reset every x seconds.
As soon as the sortTickets function is called, I will sort and reset this collection by:
Tickets = Tickets.OrderBy(c => c.Name).ToList(); //for example
When the Tickets collection is loaded again, I will check if it should be sorted and sort it before setting the Tickets property.
This feels a bit hacky because I am basically setting the collection at two points - upon loading and upon sorting. Moreover, upon loading I am using the ReactiveUI helper -> ToProperty:
LoadTickets.RegisterAsyncFunction(x => loadTickets())
.ToProperty(this, x => x.Tickets);
Whereas, upon sorting I am doing that myself:
Tickets = Tickets.OrderBy(model.Selector).ToList();
I am wondering if there is a better way to do the sorting using the ReactiveUI approach which I already use upon loading.
Thanks in advance!
Another way to solve this is via CreateDerivedCollection:
SortedTickets = Tickets.CreateDerivedCollection(
x => new TicketViewModel(x),
orderer: (l,r) => SortModel.Selector(l, r), // Returns CompareTo() result
signalReset: this.WhenAny(x => x.SortModel, x => x.Value)); // Reorder on SortModel change
Note that this breaks down if Tickets is set repeatedly (which in this case it is) - you might change your model to initializing Tickets in the ctor, then Clearing and Adding all the items, i.e.
LoadTickets.RegisterAsyncFunction(x => loadTickets())
.Subscribe(x => {
// TODO: Make sure Tickets is a ReactiveCollection
Tickets.Clear();
Tickets.AddRange(x); // Will trigger resorting of SortedTickets
});
Just had a look on Ana's blog http://blog.paulbetts.org/index.php/2010/07/05/reactivexaml-series-implementing-search-with-observableaspropertyhelper/
//
// This is the canonical way to make a read-only property whose value
// is backed by an IObservable
//
ObservableAsPropertyHelper<List<FlickrPhoto>> _Photos;
I think the read-only is the important point there.
Instead you could try using a normal observable where you can use OnNext to push in the new value
private Observable<List<TicketModel>> _Tickets = new Observable<Lis<TicketModel>>();
_Tickets.OnNext(newValue);
Or use a ObservableForProperty<> and just use the property normally
public List<TicketModel> _Tickets { get;set;}
private Observable<List<TicketModel>> _ticketsObservable= ObservableForProperty<..>(x=>x.Tickets);
Both of these methods expose an Observable which we can use later in the sort.
Why not try handling the two inputs into your sort in the same way, then it wont feel so hacky. That way you'll also have an
public SortModel SortModel {get;set;}
Your sort command implementation becomes
SortByCommand.Subscribe(c => _Sort = c));
but then you subsribe to both ticket changes AND sort criteria changes in one, see http://rxwiki.wikidot.com/101samples#toc44 for CombineLatest
new ObservableForProperty<..>(x=>x.SortModel)
.CombineLatest(_ticketsObservable)
.Subscribe( (x,y)=>
{
//Refactor to SortMethod
_tickets = y.OrderBy(x.Selector);
});
I'm pretty sure that the result of OrderBy(..) is an IEnumerable instead of an ObservableCollection. Fortunately though, it has a constructor that can do the conversion, i.e.
Tickets = new ObservableCollection<...>(Tickets.OrderBy(...));
"Better" can be very subjective measure. Firstly you haven't explained the full lifespan of the Tickets collection and the tickets it contains, so we can't really tell.
You might consider using a SortedTickets field/property instead of overwriting your tickets property which you might find you wouldn't need to be an observable collection as you would know when it needs to NotfyProperryChanged from the Tickets observable. It all depends on how frequently your tickets is likely to change.
P.S. Also make sure you have tested what happens to your sorted list when you add another ticket as you can't just
I make this async webrequest call mutliple times(can be twice or thrice or even 6 times depending on conditions)
var request = HttpWebRequest.CreateHttp(url);
var observableRequest = Observable.FromAsyncPattern<WebResponse>(
request.BeginGetResponse, request.EndGetResponse);
Observable.Timeout(observableRequest.Invoke(), TimeSpan.FromSeconds(120)).
Subscribe(response => { HandleListResult(response); },
exception => { HandleListResultTimeOut(exception); });
I have a Collection (List) in the ViewModel which has a Binding to a LisBox and i would like to keep adding to the collection after each response returns.
What is the best practice to make this happen using Reactive Extensions ? Would be great if someone can show me some sample code !
Thanks in advance
You can translate url flow directly into streams:
public static IObservable<Stream> RequestToStream(
this IObservable<string> source, TimeSpan timeout)
{
return
from wc in source.Select(WebRequest.Create)
from s in Observable
.FromAsyncPattern<WebResponse>(wc.BeginGetResponse,
wc.EndGetResponse)()
.Timeout(timeout, Observable.Empty<WebResponse>())
.Catch(Observable.Empty<WebResponse>())
select s.GetResponseStream();
}
And then you need to observe your responces on UI, you need to use .ObserveOnDispatcher(), f.e.:
Observable
.Return("www.msdn.com")
.RequestToStream(TimeSpan.FromSeconds(1))
.ObserveOnDispatcher()
.Subscribe(request => UpdateUI(Request));
In ReactiveUI, this is done via CreateCollection()
IObservable<string> source; // Maybe this is a Subject<string> or whatever
myBoundCollection = source
.SelectMany(webServiceCall) // This is your FromAsyncPattern func
.CreateCollection(); // Pipe the Observable to a Collection
ReactiveUI handles all of the ObserveOn stuff to make sure it's synchronized and on the right threads, etc. This call returns immediately with an Empty list, then as results come in, the collection gets populated.
When adding a rows to a grid, and then clicking on it, it gets selected (and highlighted). Then, clicking elsewhere but the new row remains highlighted (so now there are to highlighted rows).
Please, does anyone know what the problem could be? How to make it behave normally, i.e. clicking a row deselects (de-highlights) the other one?
After I reload the page (so the new row is not new anymore), everything works as expected.
Edit: Here's the code for adding rows:
var rec = new store.recordType({
test: 'test'
});
store.add(rec);
Edit 2: The problem seems to be listful: true. If false, it works! But I need it to be true so I'm looking at this further... It looks like as if the IDs went somehow wrong... If the ID would change (I first create the record and then the server returns proper ID, that would also confuse the row selector, no?)
(Note, correct as ExtJS 3.3.1)
First of all, this is my quick and dirty hack. Coincidentally I have my CheckboxSelectionModel extended in my system:-
Kore.ux.grid.CheckboxSelectionModel = Ext.extend(Ext.grid.CheckboxSelectionModel, {
clearSelections : function(fast){
if(this.isLocked()){
return;
}
if(fast !== true){
var ds = this.grid.store,
s = this.selections;
s.each(function(r){
//Hack, ds.indexOfId(r.id) is not correct.
//Inherited problem from Store.reader.realize function
this.deselectRow(ds.indexOf(r));
//this.deselectRow(ds.indexOfId(r.id));
}, this);
s.clear();
}else{
this.selections.clear();
}
this.last = false;
}
});
And this is the place where the clearSelections fails. They try to deselect rows by using ds.indexOfId(r.id) and it will returns -1 because we do not have the index defined remapped.
And this is why we can't find the id:-
http://imageshack.us/photo/my-images/864/ssstore.gif/
Note that the first item in the image is not properly "remapped". This is because we have a problem in the "reMap" function in our Ext.data.Store, read as follow:-
// remap record ids in MixedCollection after records have been realized. #see Store#onCreateRecords, #see DataReader#realize
reMap : function(record) {
if (Ext.isArray(record)) {
for (var i = 0, len = record.length; i < len; i++) {
this.reMap(record[i]);
}
} else {
delete this.data.map[record._phid];
this.data.map[record.id] = record;
var index = this.data.keys.indexOf(record._phid);
this.data.keys.splice(index, 1, record.id);
delete record._phid;
}
}
Apparently, this method fails to get fired (or buggy). Traced further up, this method is called by Ext.data.Store.onCreateRecords
....
this.reader.realize(rs, data);
this.reMap(rs);
....
It does look fine on the first look, but when I trace rs and data, these data magically set to undefined after this.reader.realize function, and hence reMap could not map the phantom record back to the normal record.
I don't know what is wrong with this function, and I don't know how should I overwrite this function in my JsonReader. If any of you happen to be free, do help us trace up further for the culprit that causes this problem
Cheers
Lionel
Looks like to have multi select enabled for you grid. You can configure the selection model of the grid by using the Ext.grid.RowSelectionModel.
Set your selection model to single select by configuring the sm (selection model) in grid panel as show below:
sm: new Ext.grid.RowSelectionModel({singleSelect:true})
Update:
Try reloading the grid using the load method or loadData method of the grid's store. Are you updating the grid on the client side? then maybe you can use loadData method. If you are using to get data from remote.. you can use load method. I use load method to update my grid with new records (after some user actions like add,refresh etc). Or you could simply reload as follows:
grid.getStore().reload();