I'm just getting started with silverlight.
Basically I have a silverlight user control that has various dataGrids and a combobox, their item sources set to the properties of a custom plain c# object.
My problem is that I have a dropdown list that when a user selects an item from the list a new row should appear in one of the grids.
All I'm doing is handling the SelectionChanged event and adding a new item to to a list in my custom object and setting the itemsource for the grid again. This doesnt seem to work; no row is added to the dataGrid
I have no idea how to force my grid to "rebind" to this property.
I've been reading about dependency properties, are these what I need?
Any pointers would be really appreciated.
The list you are binding against should be of the type ObservableCollection. Then the datagrid should display the new item automatically .
The problem is that when you assign the same List to the ItemsSource the DataGrid knows its the same List so it does nothing.
As Henrik points out you should expose an Observable<T> not a List<T> for properties that are to be bound to ItemsSource properties of multi-item controls such as DataGrid, ListBox etc.
In addition your "plain c# objects" should implement the INotifyPropertyChanged interface if you want changes made by code to these properties to automatically appear in the UI.
What you probably want to do is update the binding source - which is relatively easily done.
private void ComboBox_SelectionChanged(object sender, RoutedEventArgs e)
{
this.dataGrid.GetBindingExpression(DataGrid.ItemsSource).UpdateSource();
}
This is a tad hack-y but will do what you need it to do. Implementing INotifyPropertyChanged is another great suggestion.
Silverlight show have some great info on INotifyPropertyChanged here
Related
How can I get multiple instances of a usercontrol without the viewmodel being shared? Each usercontrol (and thus viewmodel) should be an instance of its own.
I have read a solution in this question: MVVMLight UserControl View Model-Create new Instance of User control for each view but I cannot get it to work!
I have a listview and a tabcontrol. When I click an item of the listview a new tab must be created with as content the usercontrol which holds information from the selected listitem. The problem is that when selecting multiple items all the items contain the information from the last selected item.
This is my viewmodellocator:
public DossierDetailViewModel DossierDetail
{
get
{
return new DossierDetailViewModel();
}
}
And I call the new usercontrol like this:
DossierDetailViewModel newDossier = new DossierDetailViewModel();
newDossier.TabName = SelectedDossier.Omschrijving;
this.OpenDossiers.Add(newDossier);
Messenger.Default.Send<DTO.Dossier.Dossier>(SelectedDossier, "SetDossier");
EDIT:
Is there no one who can help me or put me in the right direction? :(
The answer of this problem can be found here: https://mvvmlight.codeplex.com/discussions/577555
I have a user control with 2 grids on it. Now I want to be able to retrieve the grid that has the focus and expose it to my view model. How can I do this in WPF?
I want to fill a property in my view model with the name of the Grid that has focus. It seems not to be easy.
Can anyone help?
Thx!
You really should reconsider your design if you are exposing UI elements or specific parts to your viewmodel. Usually your viewmodel should not know of any specific ui element. What exactly do you want to do with the name of the ui element? You could listen to a GotFocus event on your two grids
like
<Grid x:Name="Grid1" GotFocus="OnGridGotFocus"/>
<Grid x:Name="Grid2" GotFocus="OnGridGotFocus"/>
and add this method to your UserControl, in this method you could retrieve it via
private static void OnGridGotFocus(object aSender, RoutedEventArgs aE)
{
string name = (string)(aSender as DependencyObject).GetValue(NameProperty);
}
the name could now be written into a DependencyProperty which you bind to your view model. But again, i still think you should not do this.
If you explain what exactly you are trying to achieve, maybe we can help you better.
Hi i am having some troube with DataTables. So What i need is to detect whenever i change any cell in the DataGrid of the DataTable that is binded.
How to do it? With INotifyPropertyChanged or with INotifyCollectionChanged?
Note: I am trying with INotifyPropertyChanged but it only detects when i set some value in the DataTable, and never when i change any value of any cell in the DataGrid, i already have tried OneWay and TwoWay but nothing happens.
Thanks in advance!
The datagrid would be bound to a list of objects. If you want the grid to update when individual object properties change, than each contained object must implement the INotifyPropertyChanged interface.
The INotifyCollectionChanged is an interface that the collection should implement, and are for notifications of addition and removal events.
See the section "How to implement collections" on this page.
Here's a way to approach your problem:
Create a new class that exposes the properties currently held in each DataRow. On this class implement INotifyPropertyChanged.
Instead of a DataTable, use an ObservableCollection<T> or your new class.
ObservableCollection already implements INotifyCollectionChanged, so this saves you the effort of implementing it yourself.
if you set the itemssource of your datagrid to a datatable then wpf create a IBindingListView wich is bound to the datagrid.
what you can do now is edit,add and delete items to your datatable via datagrid. if you wanna know when a cell in your datatable is changed you can subscribe to DataTable.ColumnChanged event.
why do you want do know when a cell is changed?
The answer to the title of your question is : Neither. Actually you do not need to bind a DataTable to a DataGrid. You bind a DataView. "The ADO.NET DataView implements the IBindingList interface, which provides change notifications that the binding engine listens for."(Binding Sources Overview)
One answer to your question is :
You modify the datagrid cell with a TextBox (usually). Do this with a new textbox inheriting from TextBox and override the OnGotFocus and OnLostFocus methods of it.
I have user control to which I bind a viewmodel, this implements the INotifyPropertyChanged, thru the datacontext, this has a property that is a IList that I bind to the itemsdatasource of a grid, then on the code, in another class I add some values to the list, but the UI doesn't reflect this change although in debug I can see that the datagrid has this items added but they don't appear in the UI, can anybody help me, I can't see what is the problem.
ObservableCollection<T> is your friend. It implements INotifyCollectionChanged, saving you the trouble.
I want to display a bunch of Objects i have created in a ListBox. My objects implement the INotifyPropertyChanged Interface.
I tried to use an ObservableCollection, which i have bound to a listbox Control (listbox1.DataContext = MyCollection)
But this does not exactly what i want to do, because the Listbox is not refreshed when one of the properties of one of my objects in MyCollection changes.
I have found this blogposting: http://sweux.com/blogs/psampaio/index.php/2009/04/13/creating-a-custom-observable-collection-in-wpf
is this realy the easyiest/only way to keep track of several objects?
I'm not sure, but have you tried using a datatemplate for your listbox items? like, a textbox that explicitly sets it's text to the appropriate binding.