I'm new to ReactiveUI and I'm trying to add bits of it to my Xamarin Forms application. We have a service method that returns an IObservable.
IObservable<List<DiningArea>> diningAreaObservable = _tableService.GetAllDiningAreas();
This works and previously we've subscribed to this and mapped the results into an ObservableCollection. I'd like to replace this and start using Dynamic Data. So I've setup some global's with the XAML collection view's binding source being DiningAreas.
private SourceCache<DiningArea, int> _diningAreas = new SourceCache<DiningArea, int>(x => x.Id);
private ReadOnlyObservableCollection<DiningArea> _diningAreaCollection;
public ReadOnlyObservableCollection<DiningArea> DiningAreas => _diningAreaCollection;
Now in my ViewModel I call the service, get back an observable but how do I add the observable to the SourceCache. I can see how to convert it to an IChangeSet but I want it to be apart of _diningAreas.
IObservable<List<DiningArea>> diningAreaObservable = _tableService.GetAllDiningAreas();
IObservable<IChangeSet<DiningArea, int>> diningAreaChangeSet = diningAreaObservable.ToObservableChangeSet(t => t.Id);
_diningAreas.AddOrUpdate(new DiningArea { Id = 0, Name = "All", Position = 0 });
var diningAreaDisposable = _diningAreas.Connect()
.Sort(SortExpressionComparer<DiningArea>.Ascending(z => z.Position))
.Bind(out _diningAreaCollection)
.Subscribe();
Am I understanding this correctly or am I doing something backwards?
Related
I have implemented group observable collection like below.
Grouped Property
private ObservableCollection<Grouping<String, Request>> _groupedList = null;
public ObservableCollection<Grouping<String, Request>> GroupedList {
get {
return _groupedList;
}
set {
_groupedList = value;
RaisePropertyChanged(() => GroupedList);
}
}
Creating List
var list = new List<Request>();
var grouped = from Model in list
group Model by Model.Done into Group
select new Grouping<string, Request>(Group.Key, Group);
GroupedList = new ObservableCollection<Grouping<string, TModel>>(grouped);
Now i need to update one item in the list without reloading full list for performance.
i did tried like this , mylist.FirstOrDefault(i => i.Id== mymodel.Id); Not worked for me.
I need to pick that particular item and edit and update into the list again using linq or something but i stuck here for group observable collection no efficient details to do this., anybody having idea about this help please.
And finally i get updated single item, but i need to do that without
GroupedList = new ObservableCollection<Grouping<string, TModel>>(grouped);
Because everytime it create new list and bind into my view.Thats again big performance though.
Thanks in advance.
What I understand from your question is that you want to push an updated group without overwriting the entire ObservableCollection.
To do that:
var targetGroup = GroupedList.FirstOrDefault(i => i.Id == mymodel.Id);
var targetIndex = GroupedList.IndexOf(targetGroup);
var modifiedGroup = ... //Do whatever you want to do
GroupedList[targetIndex] = modifiedGroup;
This will trigger a 'replace' operation of the target grouping.
I am using ReactiveUI 4.1. I use a ReactiveCollection of selectable items (having IsSelected flag) as a source for another derived reactive collection that uses filter to view only items that have IsSelected == true. If the source collection is pre-populated with some un/selected items before creating the derived collection, the view filter seems to work, but when later on items in the source collection go from selected to unselected state these items do not "disappear" within the derived collection. I do set ChangeTrackingEnabled flag to true on all of the collection, but it does not seem to help. Attaching my code snippet:
private readonly ReactiveCollection<string> _sourceItems = new ReactiveCollection<string>();
private readonly ReactiveCollection<SelectableDataItem<string>> _selectableItemsView = null;
private readonly ReactiveCollection<SelectableDataItem<string>> _selectedItemsView = null;
private readonly ReactiveCollection<string> _selectedDataView = null;
///....
this._sourceItems.ChangeTrackingEnabled = true;
this._selectableItemsView =
this.SourceItems.CreateDerivedCollection<string, SelectableDataItem<string>>(i => new SelectableDataItem<string>(i) { IsSelected = true, });
this._selectableItemsView.ChangeTrackingEnabled = true;
this._selectedItemsView =
this._selectableItemsView.CreateDerivedCollection<SelectableDataItem<string>, SelectableDataItem<string>>(
i => i,
f => f.IsSelected,
(i1, i2) => 0
);
this._selectedItemsView.ChangeTrackingEnabled = true;
this._selectedDataView =
this._selectableItemsView.CreateDerivedCollection<SelectableDataItem<string>, string>(i => i.Data, f => f.IsSelected, (i1, i2) => 0);
this._selectedDataView.ChangeTrackingEnabled = true;
Hmmm, looks like a bug - can you do one of the following:
Create a sample app that hits this bug, then create an issue
(Even better) Create a pull request against ReactiveUI with a test that fails
I have this bit of code that does not work because Entity Framework doesn't recognize the CreateItemDC method. CreateItemDC is a modular private method that creates a data contract for the given Item entity. I use CreateItemDC all throughout my service whenever I need to return an Item data contract, but I can't use it here. I can realize the sequence of ProjectItems into an array or enumerable because I would have to do this to all ProjectItem entities in my database as the query criteria is specified on the client and I don't have access to it here. Do I have any better options here? It seems that RIA Services is not worth the trouble. I'm really wishing I had used plain WCF with this project.
[Query]
public IQueryable<ProjectItemDC> GetProjectItems()
{
return from projectItem in ObjectContext.ProjectItems
select new ProjectItemDC
{
ID = projectItem.ID,
LibraryItem = CreateItemDC(projectItem.LibraryItem),
LibraryItemID = projectItem.LibraryItemID,
ProjectID = projectItem.ProjectID,
Quantity = projectItem.Quantity,
Width = projectItem.Width,
Height = projectItem.Height,
Depth = projectItem.Depth,
SheetMaterialID = projectItem.SheetMaterialID,
BandingMaterialID = projectItem.BandingMaterialID,
MaterialVolume = projectItem.MaterialVolume,
MaterialWeight = projectItem.MaterialWeight
};
}
P.S. I do love LINQ and E.F. though. :)
Well, if you want to go with plain WCF, you can, no problem, just change the code to
[Query(IsComposable=false)]
public IEnumerable<ProjectItemDC> GetProjectItems(string myParm1, string myParm2)
{
return from projectItem in ObjectContext.ProjectItems
select new ProjectItemDC
{
ID = projectItem.ID,
LibraryItem = CreateItemDC(projectItem.LibraryItem),
LibraryItemID = projectItem.LibraryItemID,
ProjectID = projectItem.ProjectID,
Quantity = projectItem.Quantity,
Width = projectItem.Width,
Height = projectItem.Height,
Depth = projectItem.Depth,
SheetMaterialID = projectItem.SheetMaterialID,
BandingMaterialID = projectItem.BandingMaterialID,
MaterialVolume = projectItem.MaterialVolume,
MaterialWeight = projectItem.MaterialWeight
}.ToArray();
}
write your own filtering/sorting logic and you're done.
Yes, you've lost WCF Ria Services dynamic query capabilities, but this is pretty much what you get with plain old WCF, isnt'it ?
If you instead need WCF Ria dynamic sorting/filtering/grouping you must take some additional steps, involving the visit of the Expression that WCF Ria Services create for you.
HTH
You can call ToArray() against ObjectContext.ProjectItems to force EF to load all the items, however, your query will no longer be composable on the client.
[Query]
public IQueryable<ProjectItemDC> GetProjectItems()
{
return from projectItem in ObjectContext.ProjectItems.ToArray()
select new ProjectItemDC
{
ID = projectItem.ID,
LibraryItem = CreateItemDC(projectItem.LibraryItem),
LibraryItemID = projectItem.LibraryItemID,
ProjectID = projectItem.ProjectID,
Quantity = projectItem.Quantity,
Width = projectItem.Width,
Height = projectItem.Height,
Depth = projectItem.Depth,
SheetMaterialID = projectItem.SheetMaterialID,
BandingMaterialID = projectItem.BandingMaterialID,
MaterialVolume = projectItem.MaterialVolume,
MaterialWeight = projectItem.MaterialWeight
};
}
Edit:
As mentioned in your comment, it gets all of the data out of the database at once which is not ideal. In order to create the LibraryItem with your private method, you cannot compose the query on the client. Instead, you should filter within the query method and then create the array.
[Query]
public IQueryable<ProjectItemDC> GetProjectItems(int id, string filter, object blah)
{
var projectItems = ObjectContext.ProjectItems.Where(...).ToArray();
return projectItems.Select(projectItem => new ProjectItemDC{...};
}
I'm trying to project parts of a Display and its list of locations from a WCF Data service into a custom type. Is this doable in WCF Data Services in a Silverlight client? There is some help here, but it doesn't show getting a list back as well as simple strings.
Currently I'm getting "NotSupportedException: Constructing or initializing instances of the type UserQuery+Info with the expression d.Base.Title is not supported.".
It would be a bonus if you could tell me how to do Expand on Locations in this syntax (I know about Displays.Expand("Locations")) or if I need it.
LINQPad snippet
var displays = from d in Displays.Where(d => d.Id == 3136)
select new Info
{
Name = d.Base.Title,
};
displays.Dump();
}
public class Info
{
private string name;
public string Name
{
get
{
return this.name;
}
set
{
this.name = value;
}
}
public IEnumerable<Location> locations;
public IEnumerable<Location> Locations
{
get{ return this.locations;}
set{ this.locations = value;}
}
The problem is that you are effectively asking your WCF server to construct some type it has no knowledge about. Since it is unable to do so, you have to it yourself on your computer:
Displays
.Where(d => d.Id == 3136)
.AsEnumerable()
.Select(d => new Info { Name = d.Base.Title })
This will run the Where() on the server, but the Select() on your computer.
As already noted by svick you can't ask the server for types it doesn't understand (at least not using OData that is). But you can still only ask for properties you want and nothing more.
Since I don't have your service available the below sample uses the demo service on odata.org:
DemoService ctx = new DemoService(new Uri("http://services.odata.org/OData/OData.svc/"));
var q =
ctx.Products
.Where(p => p.ID == 1)
.Select(p =>
new Product
{
Category = new Category
{
Name = p.Category.Name
}
});
var r =
q.AsEnumerable()
.Select(p =>
new
{
CategoryName = p.Category.Name
});
The first query "q" will run compoletely on server (except for creation of the client side objects) and it will only get the Name of the category (and metadata about all the entities in question). It will translate to URL like /Products(1)?$expand=Category&$select=Category/Name.
The second query starts with the AsEnumerable, which effectively executes the first query and then it just performs a simple transform into an anonymous type. This is done completely on the client (no server interaction).
I use EF code-first 4.1. in my application. Now I want to get entities through WCF services using generic types.
I'm trying to reflect generic type and invoke the method ToList of DbSet Object.
Here is my code:
public string GetAllEntries(string objectType)
{
try
{
var mdc =
Globals.DbConnection.Create(#"some_db_connection", true);
// Getting assembly for types
var asob = Assembly.GetAssembly(typeof(CrmObject));
// getting requested object type from assembly
var genericType = asob.GetType(objectType, true, true);
if (genericType.BaseType == typeof(CrmObject))
{
// Getting Set<T> method
var method = mdc.GetType().GetMember("Set").Cast<MethodInfo>().Where(x => x.IsGenericMethodDefinition).FirstOrDefault();
// Making Set<SomeRealCrmObject>() method
var genericMethod = method.MakeGenericMethod(genericType);
// invoking Setmethod into invokeSet
var invokeSet = genericMethod.Invoke(mdc, null);
// invoking ToList method from Set<> invokeSet
var invokeToList = invokeSet.GetType().GetMember("ToList").Cast<MethodInfo>().FirstOrDefault();
//this return not referenced object as result
return invokeToList.ToString();
}
return null;
}
catch (Exception ex)
{
return ex.Message + Environment.NewLine + ex.StackTrace;
}
}
In fact then I write the code like return mdc.Set<SomeRealCrmObject>().ToList() - works fine for me! But then I use the generic types I cannot find the method ToList in object DbSet<SomeRealCrmObject>().
Eranga is correct, but this is an easier usage:
dynamic invokeSet = genericMethod.Invoke(mdc, null);
var list = Enumerable.ToList(invokeSet);
C# 4's dynamic takes care of the cumbersome generic reflection for you.
ToLIst() is not a member of DbSet/ObjectSet but is an extension method.
You can try this instead
var method = typeof(Enumerable).GetMethod("ToList");
var generic = method.MakeGenericMethod(genericType);
generic.Invoke(invokeSet, null);
I had a similar situation where I needed a way to dynamically load values for dropdown lists used for search criteria on a page allowing users to run adhoc queries against a given table. I wanted to do this dynamically so there would be no code change on the front or backend when new fields were added. So using a dynamic type and some basic reflection, it solved my problem.
What I needed to do was invoke a DbSet property on a DbContext based on the generic type for the DbSet. So for instance the type might be called County and the DbSet property is called Counties. The load method below would load objects of type T (the County) and return an array of T objects (list of County objects) by invoking the DbSet property called Counties. EntityList is just a decorator object that takes a list of lookup items and adds additional properties needed for the grid on the front-end.
public T[] Load<T>() where T : class
{
var dbProperty = typeof(Data.BmpDB).GetProperties().FirstOrDefault(
x => x.GetMethod.ReturnType.GenericTypeArguments[0].FullName == typeof(T).FullName);
if (dbProperty == null)
return null;
dynamic data = dbProperty.GetMethod.Invoke(BmpDb, null);
var list = Enumerable.ToList(data) as List<T>;
var entityList = new Data.EntityList<T>(list);
return entityList.Results;
}