i am working with an pageCollectionin silverlight ,i have some remove and addition work in to the pagedviewcollection's object
i was able to remove from collection as below
_pageCollection.RemoveAt(_index);
but i am not able add an item to the pageCollection .how to add an item to the _pageCollection. i feel it should be dealt with below code
_pageCollection.AddNew();
but i amnot able to get how to proceed?
If you use a PagedCollectionView you have to set a source IEnumerable. If you add it to this collection it will work (assuming that your PCV is working with a list of Products which have an id).
myPagedCollectionView = new PagedCollectionView(myCollection);
myCollection.Add(new Product(){Id=5});
If you work with AddNew you have to do it like this :
var obj = (Product)myPagedCollectionView.AddNew();
obj.Id = 5;
Hope this is what you needed.
Related
Why there is no .Net interface for ICollectionView<T>? Looking at ICollectionView it seems quite obvious to expect for ICollectionView<T>.
Am I missing something?
The ICollectionView is only implemented by the CollectionView class. The MSDN-documentation points out that the CollectionView should not even be instantiated in your code, but instead make use of the CollectionViewSource-object to get your collection view.
If you want to have your own collection of T returned in a CollectionView, you need to add your own collection (implementing IEnumerable) to the CollectionViewSource-object and get the CollectionView from there, for instance:
List<MyClass> listToView = new List<MyClass>();
MyClass x1 = new MyClass() { Name = "Fictive Name 1", Description = "Description...", Date = DateTime.Now};
MyClass x2 = new MyClass() { Name = "Fictive Name 2", Description = "Description...", Date = DateTime.Now};
MyClass x3 = new MyClass() { Name = "Fictive Name 3", Description = "Description...", Date = DateTime.Now};
listToView.Add(x1);
listToView.Add(x2);
listToView.Add(x3);
CollectionViewSource collectionViewSource = new CollectionViewSource();
collectionViewSource.Source = listToView;
ICollectionView collectionView = collectionViewSource.View;
The reason why there is no ICollectionView of T is probably because its not designed that way. The documentation points out that the CollectionView has been designed to give a different view on a collection without changing it:
You can think of a collection view as a layer on top of a binding
source collection that allows you to navigate and display the
collection based on sort, filter, and group queries, all without
having to manipulate the underlying source collection itself.
In that regard it makes sense that you can only view the collection, hence the name 'ViewCollection'.
I think it's not so obvious to expect ICollectionView of T as CollectionView's are not even meant to be instantiated in the first place (see the interesting warning below by the way, after adding some sorting abilities).
System.Windows.Data Warning: 52 : Using CollectionView directly is not
fully supported. The basic features work, although with some
inefficiencies, but advanced features may encounter known bugs.
Consider using a derived class to avoid these problems.
I think the architecture has been designed to work on a 'read-only' based level without changing its underlying datasources, as that is what grouping, filtering and navigating a data collection's is mainly focused on.
However, if you want to know exactly why, you'd probably have to speak with someone from Microsoft that worked on this part of the framework.
I create some RibbonButtons dynamically and add them to a group according to an xml file. The follwoing function is carried out as often as entries found in the xml file.
private void ExtAppsWalk(ExternalAppsXml p, AppsWalkEventArgs args)
{
RibbonButton rBtn = new RibbonButton();
rBtn.Name = args.Name;
Binding cmdBinding = new Binding("ExtAppCommand");
rBtn.SetBinding(RibbonButton.CommandProperty, cmdBinding);
Binding tagBinding = new Binding("UrlTag");
tagBinding.Mode = BindingMode.OneWayToSource;
rBtn.SetBinding(RibbonButton.TagProperty, tagBinding);
rBtn.Label = args.Haed;
rBtn.Tag = args.Url;
rBtn.Margin = new Thickness(15, 0, 0, 0);
MyHost.ribGrpExtern.Items.Add(rBtn);
}
I tried to use the Tag property to store the Url's to be started when the respective button is clicked. Unfortunately the binding to the Tag property gives me the last inserted Url only.
What would be the best way to figure out which button is hit or to update the Tag property.
The datacontext is by default the context of the Viewmodel. The RibbonGroup to which the Buttons are added is created in the xaml file at designtime. I use that construct:
MyHost.ribGrpExtern.Items.Add(rBtn);
to add the buttons. It maight not really be conform with the mvvm pattern. May be someone else has a better idea to carry that out.
I foud a solution for my problem here and use the RelayCommand class. So I can pass objects (my Url) to the CommandHandler.
RibbonButton rBtn = new RibbonButton();
rBtn.Name = args.Name;
Binding cmdBinding = new Binding("ExtAppCommand");
rBtn.SetBinding(RibbonButton.CommandProperty, cmdBinding);
rBtn.CommandParameter = (object)args.Url;
private void ExtAppFuncExecute(object parameter)
{
if (parameter.ToString().....//myUrl
I am working on a WPF app using the MVVM patterm, which I am learning. It uses EF4. I am trying to use a similar tabbed document interface style; several combo boxes on these tabs have the same items sources (from a sql db). Since this data almost never changes, it seemed like a good idea to make a repository object to get them when the app starts, and just reuse them for each viewmodel. For whatever reason though, even though I use new in the constructors, the lists are connected.
If I set a bound combo box on one tab, it gets set on another (or set when a new tab is created). I don't want this to happen, but I don't know why does.
The repository object is initialized before anything else, and just holds public lists. The views simply use items source binding onto the ObservableCollection. I am using the ViewModelBase class from the article. Here is the Viewmodel and model code.
ViewModel
TicketModel _ticket;
public TicketViewModel(TableRepository repository)
{
_ticket = new TicketModel(repository);
}
public ObservableCollection<Customer> CustomerList
{
get { return _ticket.CustomerList; }
set
{
if (value == _ticket.CustomerList)
return;
_ticket.CustomerList = value;
//base.OnPropertyChanged("CustomerList");
}
}
Model
public ObservableCollection<Customer> CustomerList { get; set; }
public TicketModel(TableRepository repository)
{
CustomerList = new ObservableCollection<Customer>(repository.Customers);
}
EDIT: I am sure this is the wrong way to do this, I am still working on it. Here is the new model code:
public TicketModel(TableRepository repository)
{
CustomerList = new ObservableCollection<Customer>((from x in repository.Customers
select
new Customer
{
CM_CUSTOMER_ID = x.CM_CUSTOMER_ID,
CM_FULL_NAME = x.CM_FULL_NAME,
CM_COMPANY_ID = x.CM_COMPANY_ID
}).ToList());
}
This causes a new problem. Whenever you change tabs, the selection on the combo box is cleared.
MORE EDITS: This question I ran into when uses Rachels answer indicates that a static repository is bad practice because it leaves the DB connection open for the life of the program. I confirmed a connection remains open, but it looks like one remains open for non-static classes too. Here is the repository code:
using (BT8_Entity db = new BT8_Entity())
{
_companies = (from x in db.Companies where x.CO_INACTIVE == 0 select x).ToList();
_customers = (from x in db.Customers where x.CM_INACTIVE == 0 orderby x.CM_FULL_NAME select x).ToList();
_locations = (from x in db.Locations where x.LC_INACTIVE == 0 select x).ToList();
_departments = (from x in db.Departments where x.DP_INACTIVE == 0 select x).ToList();
_users = (from x in db.Users where x.US_INACTIVE == 0 select x).ToList();
}
_companies.Add(new Company { CO_COMPANY_ID = 0, CO_COMPANY_NAME = "" });
_companies.OrderBy(x => x.CO_COMPANY_NAME);
_departments.Add(new Department { DP_DEPARTMENT_ID = 0, DP_DEPARTMENT_NAME = "" });
_locations.Add(new Location { LC_LOCATION_ID = 0, LC_LOCATION_NAME = "" });
However, now I am back to the ugly code above which does not seem a good solution to copying the collection, as the Customer object needs to be manually recreated property by property in any code that needs its. It seems like this should be a very common thing to do, re-using lists, I feel like it should have a solution.
Custom objects, such as Customer get passed around by reference, not value. So even though you're creating a new ObservableCollection, it is still filled with the Customer objects that exist in your Repository. To make a truly new collection you'll need to create a new copy of each Customer object for your collection.
If you are creating multiple copies of the CustomerList because you want to filter the collection depending on your needs, you can use a CollectionViewSource instead of an ObservableCollection. This allows you to return a filtered view of a collection instead of the full collection itself.
EDIT
If not, have you considered using a static list for your ComboBox items, and just storing the SelectedItem in your model?
For example,
<ComboBox ItemsSource="{Binding Source={x:Static local:Lists.CustomerList}}"
SelectedItem="{Binding Customer}" />
This would fill the ComboBox with the ObservableCollection<Customer> CustomerList property that is found on the Static class Lists, and would bind the SelectedItem to the Model.Customer property
If the SelectedItem does not directly reference an item in the ComboBox's ItemsSource, you need to overwrite the Equals() of the item class to make the two values equal the same if their values are the same. Otherwise, it will compare the hash code of the two objects and decide that the two objects are not equal, even if the data they contain are the same. As an alternative, you can also bind SelectedValue and SelectedValuePath properties on the ComboBox instead of SelectedItem.
I have a problem with Linq and ObservableCollections in my WPF application.
Context of the problem:
I've created a very simple SQL database with two tables: User and BankAccounts.
The User Table has an one-to-many relationship with the BankAccounts Table. Next I've created Linq-to-SQL dataclasses, which worked fine ==> the assosiation between the two tables was detected as well.
Next I've created a function to retreive all Users which works fine:
DataClassesDataContext dc = new DataClassesDataContext
var query = from u in dc.Users
select u;
Now suppose I want to add a new BankAccount to each user (not very likely but still).
I could add the following code
for each(User u in query)
{
u.BankAccounts.Add(New BankAccount());
}
The above works all fine. The BankAccounts property is automaticly part of the User class, due to the assosiation in the database and Linq DataClasses.
However, in my application I first add the query results to an ObservableCollection. Hereby I could use all sorts off databinding and changenotification. This is accomplished by the following code;
ObservableCollection<User> oUsers = new ObservableCollection<User>(query);
Problem: Within the ObservableCollection I can't do anyting with the users BankAccounts property because it is now of type EntitySet<>. So I can't do the following statement anymore.
for each(User u in oUsers)
{
u.BankAccounts.Add(New BankAccount());
}
Somehow, when queryresults are added to an observablecollection It is not possible to acces the user.BankAccounts properties anymore. However, it is possible to bind the BankAccounts Property to any control, like a listbox, and it contains the correct data.
Does someone now how I can create an observableCollction (or similar collection) from wich I can access these "assosiated" properties? I'm realy looking forward for to a solution.
Thanks in advance!
Best regards,
Bas Zweeris
E: Bas.Zweeris#Capgemini.com
Keep track of the original query which will implement IQueryable, you can run any further queries you need against that.
The ObservableCollection should just be for WPF to have something to bind to - its very useful if you want to add a new collection item but not have it pushed to the database before the user has had chance to edit it.
eg.
// Create a new blank client type
var ct = new ClientType()
{
IsArchived = false,
Description = "<new client type>",
Code = "CT000",
CanLoginOnline = true
};
// Tell the data source to keep track of this object
db.ClientTypes.InsertOnSubmit(ct);
// Also add the object to the observable collection so that it can immediately be shown in the UI and editted without hitting the db
clienttypes.Add(ct);
I have a grid bound to a BindingSource which is bound to DataContext table, like this:
myBindingSource.DataSource = myDataContext.MyTable;
myGrid.DataSource = myBindingSource;
I couldn't refresh BindingSource after insert. This didn't work:
myDataContext.Refresh(RefreshMode.OverwriteCurrentValues, myBindingSource);
myBindingSource.ResetBinding(false);
Neither this:
myDataContext.Refresh(RefreshMode.OverwriteCurrentValues, myDataContext.MyTable);
myBindingSource.ResetBinding(false);
What should I do?
I have solved the problem but not in a way I wanted.
Turns out that DataContext and Linq To SQL is best for unit-of-work operations. Means you create a DataContext, get your job done, discard it. If you need another operation, create another one.
For this problem only thing I had to do was recreate my DataContext like this.dx = new MyDataContext();. If you don't do this you always get stale/cached data. From what I've read from various blog/forum posts that DataContext is lightweight and doing this A-OK. This was the only way I've found after searching for a day.
And finally one more working solution.
This solution works fine and do not require recreating DataContext.
You need to reset internal Table cache.
for this you need change private property cachedList of Table using reflection.
You can use following utility code:
public static class LinqDataTableExtension
{
public static void ResetTableCache(this ITable table)
{
table.InternalSetNonPublicFieldValue("cachedList", null);
}
public static void ResetTableCache(this IListSource source)
{
source.InternalSetNonPublicFieldValue("cachedList", null);
}
public static void InternalSetNonPublicFieldValue(this object entity, string propertyName, object value)
{
if (entity == null)
throw new ArgumentNullException("entity");
if(string.IsNullOrEmpty(propertyName))
throw new ArgumentNullException("propertyName");
var type = entity.GetType();
var prop = type.GetField(propertyName, BindingFlags.NonPublic | BindingFlags.Instance);
if (prop != null)
prop.SetValue(entity, value);
// add any exception code here if property was not found :)
}
}
using something like:
var dSource = Db.GetTable(...)
dSource.ResetTableCache();
You need to reset your BindingSource using something like:
_BindingSource.DataSource = new List();
_BindingSource.DataSource = dSource;
// hack - refresh binding list
Enjoy :)
Grid Data Source Referesh by new query instead just Contest.Table.
Simple Solution < But Working.
Whre is eg.
!!!!! Thanks - Problem Solved after no of days !!! but with so simple way ..
CrmDemoContext.CrmDemoDataContext Context = new CrmDemoContext.CrmDemoDataContext();
var query = from it in Context.Companies select it;
// initial connection
dataGridView1.DataSource = query;
after changes or add in data
Context.SubmitChanges();
//call here again
dataGridView1.DataSource = query;
I have the same problem. I was using a form to create rows in my table without saving the context each time. Luckily I had multiple forms doing this and one updated the grid properly and one didn't.
The only difference?
I bound one to the entity similarly (not using the bindingSource) to what you did:
myGrid.DataSource = myDataContext.MyTable;
The second I bound:
myGrid.DataSource = myDataContext.MyTable.ToList();
The second way worked.
I think you should also refresh/update datagrid. You need to force redraw of grid.
Not sure how you insert rows. I had same problem when used DataContext.InsertOnSubmit(row), but when I just inserted rows into BindingSource instead BindingSource.Insert(Bindingsource.Count, row)
and used DataContext only to DataContext.SubmitChanges() and DataContext.GetChangeSet(). BindingSource inserts rows into both grid and context.
the answer from Atomosk helped me to solve a similar problem -
thanks a lot Atomosk!
I updated my database by the following two lines of code, but the DataGridView did not show the changes (it did not add a new row):
this.dataContext.MyTable.InsertOnSubmit(newDataset);
this.dataContext.SubmitChanges();
Where this.dataContext.MyTable was set to the DataSource property of a BindingSource object, which was set to the DataSource property of a DataGridView object.
In code it does looks like this:
DataGridView dgv = new DataGridView();
BindingSource bs = new BindingSource();
bs.DataSource = this.dataContext.MyTable; // Table<T> object type
dgv.DataSource = bs;
Setting bs.DataSource equals null and after that back to this.dataContext.MyTable did not help to update the DataGridView either.
The only way to update the DataGridView with the new entry was a complete different approach by adding it to the BindingSource instead of the corresponding table of the DataContext, as Atomosk mentioned.
this.bs.Add(newDataset);
this.dataContext.SubmitChanges();
Without doing so bs.Count; returned a smaller number as this.dataContext.MyTable.Count();
This does not make sense and seems to be a bug in the binding model in my opinion.