I have a WPF window that has a datagrid and a user control for a form for the fields in that datagrid. The user control and the WPF window have view models.
The user control's DataContext is bound to one of the window's view model's member field, whose value changes during the data grid's Selection Changed event.
I'm not sure if this is the right way to do it because I am unable to create references from the inner view model to the outer view model for some reason. Constructor injection won't work because I'm required to use default constructor only, and I can't seem to put a property injector in the right place (always getting null reference when I try to use it).
I am also unable to get my property change notification to work properly in the inner view model.
Is there a better way to wire my view models so that they automatically change the values in the user control when a new row is selected in the datagrid? I have a feeling that binding to the control's DataContext is not the way to go.
This doesn't seems a complex/nested scenario. Looks like pretty much a normal master details scenario. Suppose you want to edit Customer data, I would have an ObservableCollection instance bind to the DataGrid, and there will be a SelectedCustomer property in the VM also. In the DataGrid you can set SelectedItem twoway bind to the SelectedCustomer property which makes SelectedCustomer always updated with your selection. Since the usercontrol has the same instance of customer as in the DataGrid row, whenever you change anything in the UC those data will get reflected in the grid. Ofcourse all those properties should fire NotifypropertyChanged.
Related
i have a datagrid bound to a property. In this grid i have columns which consists of cells which are like hyperlink i mean when user clicks on the cell value based on these values another gird will get populated. i want to know how to get the cell value and pass it to some method so that other grid will get populated.
The best way to do this is in your viewmodel.
You should bind the SelectedItem of your datagrid to a new property in your ViewModel. In the set method of this new Property, call a new method to populate a new ObservableCollection/List/whatever...
Finally, bind your "other grid" ItemsSource to this new observable collection from your ViewModel.
Edit:
If you need to load one thing or another depending on the column you are going to use the code behind, take a look at this:
Silverlight DataGrid how to get cell value from a selected item?
I have a UserControl that has a DataGrid in it filled with members. The DataGrid.ItemsSource is bound to an ObservableCollection on the model. The DataGrid.SelectedItem is bound to the SelectedMember field on the model. The SelectedMember._set calls NotifyPropertyChanged and the event calls SetValue() for the exposed DependencyProperty.
This UserControl is on a page. That page has a viewmodel too. I'm trying to bind the UserControl.CurrentMember to the viewmodel.SelectedMember but it's not changing. I can bind the CurrentMember.MemberName to a textbox and the box fills with the member name so it looks like the UserControl is exposing the DependencyProperty correctly. But if I bind to the model it doesn't update.
I can't find any cross bindings. The bind to the TextBox works fine. The field on the page model is new so there's nothing bound to it.
What could be the problem? Does the field on the page model need to be a DependencyProperty? The compiler would give me an error if that were the case.
I'll try and get a code sample but it's so ingrained I can't just post a couple of lines of code.
Tom P.
After combing the code and trying to replicate the problem in a new project I found the problem.
In the UserControl I set the DataContext to the Model. But the UserControl.DataContext gets overwritten when I put it on the page. What i needed to do was name the MainGrid and set the DataContext of the MainGrid to the UserControlModel. MainGrid, being private to the UserControl, won't get overwritten. Now it works wonderfully.
I have a View with a dataGrid. This datagrid bind a property in the ViewModel that is an ObservableCollection.
I edit some data in the dataGrid, and a field is updated by code, because it depends on some operations. Well, if I check the item in the observable collection, I can see that all the data is correct, but the info in the dataGrid is no refresh.
I want to force the refresh because I know that the observableCollection only raise the change property event when I add o remove items, but not if I edit one of them.
Because I am use Entity Framework 4.1, really the ItemsSource of the dataGrid is the local of the DbSet, so I don't know how to implement the notifyPorpertyChanged in the classes of the model edmx, and I am looking for an alternative, like to force refresh the dataGrid.
Because the property of the ViewModel that I use to bing the ItemsSource of the dataGrid is a reference to the local, I mean that to set the property I do myProperty = myContext.MyTable.Local and that raise the event PropertyChanged that I implement in my ViewModel, I try to do myProperty = myContext.MyTable.Local again to try to raise the event and force the refresh of the dataGrid, but it does not work.
What alternatives do I have?
Make sure that you have the Binding Mode set to TwoWay. Implement in the set portion of your property OnPropertyChanged and the rest should take care of itself.
I have a silverlight datagrid to which I am binding an observable collection from the viewmodel. There is a detail view page which will display different properties of the object in the collection when user selects a row of the datagrid. My requirement is when user updates any properties in the detail view; the data should be updated in the data grid also. How to implement this functionality?
Well, the answer is simply to bind both the datagrid row and the control displaying the selected object. The simplest way is to use a ICollectionView (returned by a CollectionViewSource from the original ObservableCollection), bind the grid's ItemsSource to that, and then bind the control's DataContext to the ICollectionView's CurrentItem. That way, when the grid's selected item changes, the CurrentItem of the ICollectionView is updated, and that item is displayed in the detail view.
I think it's quite easy but if you need additional details or sample source code I'll elaborate.
Kind of an odd question- if I'm thinking of this the wrong way please let me know. I am using an infragistics dock manager, which manages tabs as well. So I can create a TabGroupPane, and then add multiple ContentPanes, each of which has its own tab.
In each content pane, I set my viewmodel:
<ContentPane>
<viewmodels:MyViewModelForTab1 />
</ContentPane>
So here's the problem- while using a mediator pattern for communication, my viewmodels have no idea if they are on the visible tab or not, so they are always working even if hidden. The TabGroupPane does have a SelectedTab property, as well as each ContentPane having an IsActive property.
So the question is how do I set that information in my ViewModel? Making my VM a dependency object seems like a bad idea since I already implement INotifyPropertyChanged. Using a CLR prop in my VM also doesnt work, since you cannot bind to it.
How can I get my VM to know if it is the datacontext of an active tab?
Thanks!
I would put an IsSelected property on my ViewModel and bind it to the TabItem's IsSelected dependency property.
This should allow you to hook into when it is updated and perform whatever you need. You don't need a mediator pattern here since you are communicatining from the View to the ViewModel.
Make sure your ViewModel is bound to the DataContext property of the view (specifically, that the Tab's DataContext is the ViewModel). The way you have it now, your ViewModel is the content of the element, not bound to the DataContext, as it should be:
<Tab.Resources>
<viewmodels:MyViewModelForTab1 x:Key="Tab1ViewModel" />
</Tab.Resources>
<ContentPane DataContext="{StaticResource Tab1ViewModel}" />
Or something like that...
I don't know the Infragistics model, so my apologies if this is inapposite, but here's how I implement this with regular items controls - tab control, list box, whatever.
Create a container view model class that includes an observable collection of items and exposes a SelectedItem property. Make the container class the data context of the items control. Bind the items control's SelectedItem property to the container class's.
Hook the item objects up to the PropertyChanged event of the container. So now when the selected item in the UI changes, the container view model notifies all of the items that SelectedItem has changed. Each item object's event handler can determine for itself whether or not it's now the selected item.
The item objects thus don't know any implementation details of the UI - you can unit test your classes outside of a UI and the logic will still work correctly.