I'm new to both Caliburn and WPF, so excuse me if it is a rather trivial question.
The scenario is the following:
I have multiple controls (like buttons and textboxes - the latter is the important part).
Their state (Enabled/Disabled) are dependent on a boolean property.
The first suggested method I tried was using the Can[FunctionName] convention and NotifyOfPropertyChange(() => Can[FunctionName]). It worked well with the button, but it did not work with the textbox.
How do I bind IsEnabled property to a state without using the code-behind of the View?
The code I tried in the ViewModel didn't work for the textbox:
private bool _buttonEnableState = true;
public bool ButtonEnableState
{
get
{
return _buttonEnableState;
}
set
{
_buttonEnableState = value;
NotifyOfPropertyChange(() => CanTheButton);
NotifyOfPropertyChange(() => CanTheTextBox);
}
}
public bool CanTheButton
{
get
{
return ButtonEnableState;
}
}
public void TheButton()
{
}
public bool CanTheTextBox
{
get
{
return ButtonEnableState;
}
}
From the View:
<Button x:Name="TheButton" Content="This is the button" ... />
<TextBox x:Name="TheTextBox" ... />
Thanks in advance!
Have you tried the obvious?:
<Button Content="This is the button" IsEnabled="{Binding ButtonEnableState}" />
<TextBox x:Name="TheTextBox" IsEnabled="{Binding ButtonEnableState}" />
UPDATE >>>
So, continuing the conversation from the comments... now you have a public property in your AppViewModel class and an instance of that class is set as the DataContext of your view that contains the Button and TextBox controls?
Let's see if the Binding is really working or not... try changing your code to this:
<Button Content="{Binding ButtonEnableState}" />
If the Button.Content is set then the Binding works just fine and you have a different problem.
UPDATE 2 >>>
As #Charleh mentioned, you also need to make sure that you have notified the INotifyPropertyChanged interface of the change of property value:
NotifyOfPropertyChange(() => ButtonEnableState);
I don't think what I'm about to suggest is necessarily the correct way of doing things, but it may give you the result you're after.
In order to get the control to be disabled based on a Can<name> property, you need to confirm to the conventions that Caliburn uses, so in this case, supplying a function <name> should work:
public void TheTextBox()
{
}
As a result of the default conventions, I believe this will be called every time the KeyDown event is fired.
That said, you probably want to bind your text content to something, and you'll want to use the x:Name property convention to choose which property, that means you'll have to attach the TheTextBox() function in a different way, you should be able to do that using the Message.Attach property in the Caliburn namespace.
So your TextBox could look like this (where you've added the following namespace xmlns:cal="http://www.caliburnproject.org"):
<TextBox cal:Message.Attach="TheTextBox" Name="SomeTextProperty" />
Backing that up in your ViewModel, you'd have:
// Your Enabled Property (using your existing code).
public bool CanTheTextBox
{
get
{
return ButtonEnableState;
}
}
// Your dummy function
public void TheTextBox()
{
}
// Some text property (Just for demo, you'd probably want to have more complex logic in the get/set
public string SomeTextProperty
{
get; set;
}
You should then see the Enabled/Disabled behaviour, and be use the SomeTextProperty.
I'm not entirely sure I like this way of doing things, I just had a quick play to see if it worked. The following answer might be a cleaner solution, and establishes a new re-usable convention:
Adding a convention for IsEnabled to Caliburn.Micro
As a slight aside (not a direct answer), depending on how complicated your control/form is, you could investigate using multiple Views for the same ViewModel, in the past I've set up a ReadOnly and Editable view, and used a single property on the ViewModel to toggle between the two (essentially setting the entire state of the ViewModel). There are already default conventions so you can use multiple views with relative ease.
Related
In my code, I have an UIElement variable I set with certain button presses.
Now, I have this variable:
public UIElement currentMenu;
Set to this value:
currentMenu = (UIElement)Resources["Home"];
I get it from the Resources so I don't have to manage it messily in the code-behind, I will export the Resources to a seperate ResourceDictionary once I get this problem solved.
My SplitView looks like this:
<SplitView x:Name="NavPane" OpenPaneLength="250" CompactPaneLength="50" Content="{x:Bind currentMenu}" DisplayMode="CompactOverlay" IsPaneOpen="False" PaneClosing="NavPane_PaneClosing">
The prblem comes in at this point, the Binding crashes the entire application with an unhndled win32 exception. I get no description and the error code changes every time. I have checked with break points whether this behaviour is actually caused by the binding, and it is.
If you have any suggestions on what might be going wrong here, please post an answer. I will supply any additional information needed (if reasonable, I'm not going to send you my entire project files)
Any help is appreciated!
Your problem that you are using a variable, not a property.
private UIElement currentMenu;
public string CurrentMenu
{
get { return currentMenu; }
set {
currentMenu=value);
OnPropertyChanged("CurrentMenu");
}
}
So the basic rules to bind Control to a "varaible":
Variable should be a property, not a field.
it should be public.
Either a notifying property (suitable for model classes) or a dependency property (suitable for view classes)
To notify UI you should implement INotifyPropertyChanged:
public event PropertyChangedEventHandler PropertyChanged;
public void OnPropertyChanged(string propertyName)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
Update:
Your Bidning should looks like:
<SplitView x:Name="NavPane" OpenPaneLength="250" CompactPaneLength="50"
Content="{Binding CurrentMenu}" DisplayMode="CompactOverlay" IsPaneOpen="False"
PaneClosing="NavPane_PaneClosing">
I have found the answer to my question!
Namely, this was not the way to do it. Instead, I declared a Frame inside the Content of the SplitView:
<SplitView.Content>
<Frame x:Name="activeMenu"/>
</SplitView.Content>
Then, I use the Frame.Navigate() function to load my menus into the Frame:
public MainPage()
{
DataContext = this;
this.InitializeComponent();
SetMenu(0);
}
private void SetMenu(int key)
{
switch (key)
{
case 0:
activeMenu.Navigate(typeof(HomeMenu));
break;
//You can add in as many cases as you need
}
}
What you then need is to set all the menus you want as separate Pages within your project files. in this example, HomeMenu.xaml contains the grid for the menu people see upon starting up the app.
This solved the problem, but thank you to everyone (StepUp) who contributed to the original (unfortunately unsuccessful) solution!
I'm trying to create a game editor in C#/WPF. The editor consists of a user control that shows the scene (rendered in OpenGL using SharpGL) as well as many controls for editing the current scene and objects. Objects consist of components whose properties can be edited in the editor (kind of like in Unity game engine). I already have a "component editor" view which uses reflection to find all properties on the component and creates a property editor (for example, a slider) per each property. However, I'm not sure how to bind the properties between UI and code.
The problem is, I want these properties to be updated in the UI when they change in code, as well as updated in code when they're changed in the UI. If I want to bind the editor controls (such as a slider that changes a property) to the component properties, they would have to implement NotifyPropertyChanged, which would be quite cumbersome. I guess the other way is doing dirty-checking, but I'm not sure if that's a good idea either.
Can anybody give me pointers on how this property updating between UI/Code should be handled? I want it to work pretty much like it does in Unity, where you don't need to write anything extra into your component class to make properties editable.
EDIT: To make more clear what I'm trying to achieve and already have, here is a part of the "component editor" user control. It's datacontext is a Component instance (model). PropertiesConverter returns it's properties (through component.GetType().GetProperties()). ComponentPropertyTemplateSelector decides on the property editor user control (for example, for a double property it would select a "number editor" that has a textbox for editing the value). The problem that I'm interested in solving is how to two-way bind a Component's property to an editor control.
<ItemsControl x:Name="ComponentProperties" Grid.Row="1" ItemTemplateSelector="{StaticResource ComponentPropertyTemplateSelector}">
<ItemsControl.ItemsSource>
<Binding Converter="{StaticResource PropertiesConverter}"/>
</ItemsControl.ItemsSource>
</ItemsControl>
I would say you probably want to follow the MVVM pattern which does use the INotifyPropertyChanged interface. If you do a Google search on MVVM there are some good articles that come up right away. There are also some existing tools out there already to help get you started. From what you describe in your question the MVVM pattern essentially works that way. It decouples the UI and the code but still maintains that connection. The real quick version is that you implement the INotifyPropertyChanged on a class and then you set an instance of that class to the DataContext of the control you want to setup the binding for. Probably easier to see an example:
Xaml:
<StackPanel>
<Slider Value="{Binding SliderValue, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />
<TextBox Text="{Binding MyText, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>
<TextBox Text="{Binding MyText, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>
<Slider Value="{Binding SliderValue, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />
</StackPanel>
I created a view model base to save on some code writing:
class ViewModelBase : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
var handler = this.PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
}
An example view model class:
class MyViewModel : ViewModelBase
{
private int sliderValue;
private string myText;
public int SliderValue
{
get { return this.sliderValue; }
set
{
this.sliderValue = value;
this.OnPropertyChanged();
}
}
public string MyText
{
get { return this.myText; }
set
{
this.myText = value;
this.OnPropertyChanged();
}
}
}
How to hook up the binding (in this case the code behind of the control):
public MainWindow()
{
InitializeComponent();
this.DataContext = new MyViewModel();
}
As you can see there is some work involved in setting up the view models and xaml. Compared to other solutions I think this is pretty good as far as the amount of "work" you have to put in. I don't know if there is any way to get around it though and have it work like "magic". It might be worth checking into what MVVM tools exist, there may be stuff out there that can make things even more simple.
You can add IPropertyChangeNotification support automatically using either Castle Dynamic Proxy (which wraps the classes in a proxy) or Fody (which modifies the IL in a post-build step).
I have a simple use case which I am struggling with in Caliburn.Micro. I can get this to work easily with traditional bindings, but I'd like to use the framework properly.
In short, this is an MDI style app with a single top level toolbar of which I'd like to bind the context to the Conductor.ActiveItem. Basically, the issue I'm seeing is that Calibun set up the Actions for the toolbar buttons for the first opened tab, but later when ActiveItem is changed, the connected actions continue to point to the first assigned ActiveItem and not the new one.
My main ViewModel is of type Conductor.Collection.OneActive.
public sealed class MainViewModel : Conductor<ITabPage>.Collection.OneActive
{
}
This view model contains a simple list of tabs each with public methods Save() and Undo() (along with bool property implementations for CanSave and CanUndo).
public interface ITabPage : IScreen, IDisposable
{
void Save();
void Undo();
bool CanSave { get; }
bool CanUndo { get; }
}
Now the view contains the top-level toolbar with buttons invoking the actions on the ActiveItem and a TabControl to display the conductor items.
<Window xmlns:cal="http://www.caliburnproject.org" ...>
<DockPanel>
<ToolBar DockPanel.Dock="Top" cal:Bind.Model="{Binding ActiveItem}">
<Button Name="Save">Save</Button>
<Button Name="Undo">Undo</Button>
</ToolBar>
<TabControl x:Name="Items">
</TabControl>
</DockPanel>
</Window>
Using normal binding and ICommands works fine, but I'd like to not fight the framework on this. Is there something I'm missing or misusing with cal:Bind.Model? Or perhaps a way to let it know to refresh? I've also tried calling Refresh() when ActiveItem is changed and I'm *absolutely" sure the CanSave and CanUndo are notifying properly (I've set break points and I've had success with normal bindings.)
Found a solution: I was misusing caliburn:Bind.Model.
The correct bind type is
caliburn:Bind.ModelWithoutContext="{Binding ... }"
Using that dependency property helper instead allows the Actions to be routed correctly to the ActiveItem as it changes.
In my MVVM test project I want to bind my textbox to the object from viewmodel:
public class ContactViewModel : BaseNotifyPropertyChanged
{
Contact _selectedItem;
public ContactViewModel()
{
ContactModel contactModel = new ContactModel();
_selectedItem = contactModel.ContactList[1]; // this contains first contact from the list;
}
}
public Contact SelectedContact
{
get
{
return _selectedItem;
}
}
in my Contact class I am overriding ToString Method in order to show first Contact's first name:
public override string ToString()
{
return _firstName.ToString();
}
And here is my XAML binding:
<TextBox Height="23" HorizontalAlignment="Left" Name="SelectedItemTextBox" Text="{Binding Path=SelectedContact}" VerticalAlignment="Top" Width="120" />
And for some reason this textbox is always empty. However, if I change
public String SelectedContact
{
get
{
return _selectedItem.LastName;
}
}
it works perfectly.
Stanislav, you did a mistake in other place. You try to bind to object, binding doesn't know what to show and apply ToString() to your Contact object. If you overrode ToString(), it had to show a returned value of this method. I created the test app, and it works in this way!
What I can see in your code, in ToString() you return FirstName, but in changed SelectedContact it is SecondName - did you fill first name before?
You wrote in comment that tried to access to first element, but in code you take second element of ContactList
Moreover, use binding in this way is incorrect. If you want to access to LastName use next way:
<TextBox Text="{Binding Path=SelectedContact.LastName, Mode=OneTime}" />
And remove ToString() overriding.
EDIT: Unlike to other controls where binding is OneWay by default in TextBox it is TwoWay by default. It was done because native behavior of TextBox is show and edit value (not only show as in other controls). Moreover if you don't plan to change value (you don't plan, because ContactModel doesn't implement INotifyPropertyChanged) it is recommended to use OneTime mode (for performance).
TwoWay has some restriction - you can't use it for read-only property (SelectedContact is read-only in your code). Because binding can't change the value in this case - make sense. It is strange that app lunched in your case and TextBox was empty, because in my case I get the error "A TwoWay or OneWayToSource binding cannot work on the read-only property 'SelectedContact' of type 'WpfApplication1.ContactViewModel'." until I changed binding mode in TextBox.
I guess you followed this Article on MSDN:
http://msdn.microsoft.com/en-us/library/ms742521%28v=vs.110%29.aspx
Alltough the article says, that the standard representation of a ListBox is a List of ToString representation of its contents, this is not the case for every other element.
I would highly recommend to create a DataBinding Template for you Contact class, it's a much cleaner way to implement this behaviour than overriding ToString.
Ah, found it, I just had to change my TextBox to the TextBlock and now everything works properly !
It seems like TextBlock does understand how to show objects, but TextBox doesn't.
I'm curious how this works, because I have a MainViewModel, which has Property say called SubViewModel which has a Property of ObservableCollection (we'll call it Property1.)
I've implemented INotifyChangedProperty on everything.
My Main Window
<Window ..
DataContext="{Binding MainViewModel}" />
...
<StackPanel DataContext="{Binding SubViewModel}">
<local:SomeControl DataContext="{Binding}" />
</StackPanel>
</Window>
And my UserControl
<UserControl Name="SomeControl">
<DataGrid Name="MyDataGrid" ItemSource="{Binding Property1, Mode=TwoWay}" CurrentCellChanged="TestMethod" />
...
</UserControl>
In my test method, just as a test to figure out why the changes are not propegating up to the main view model I do something like this
private void TestMethod()
{
var vm = this.DataContext as SubViewModel;
var itemSourceObservableCollection = MyDataGrid.ItemsSource as ObservableCollection<MyType>;
//I thought vm.Property1 would be equal to itemSourceObservableCollection
//but they are not, itemSourceObservableCollection shows the changes I've made
//vm.Property1 has not reflected any changes made, even though I though they were the same item
}
So I figured out that ItemSource must create a copy of the item you bind it to? I'm stuck here, how do manually notify the viewModel that this property has changed and it needs to update? I thought that was INotifyPropertyChanged's job?
I think part of my problem is I lack the understanding of how this kinda works internally. If anyone can point to a good blog post, or documentation to help me understand why my code isn't working the way I expected, that would be great.
1) No copy is made.
2) ObservableCollection will propogate changes made to the collection, not the items within the collection. So you'll see additions, deletions etc. but NOT property changes to items within the collection.
3) If you want to see changes made to individual items in the ObservableCollection, you need to implement INotifyPropertyChanged on those items.
There's actually TWO different issues here. What happens internally when you bind to a collection? AND why changes on the user surface are not propagated back to your View Model. Based upon what you wrote, the two issues are not connected, but let's take them one at a time...
For the first issue... When you bind a collection, the WPF binding engine creates a "CollectionView" class that mediates between your object store and the logical tree. You can, if needed, get a copy of the the "CollectionView" using a static method on CollectionViewSource...
var cvs = CollectionViewSource.GetDefaultView(MyCollectionOfThings);
There are several interesting properties in the result, and some of them contain write accessors which allow you to directory modify the CollectionView.
For the second issue... The business classes in your SubViewModel need to inherit from INotifyPropertyChanged such that changes are 'announced' via the WPF binding engine. Your VM should be a publisher, but can also be a subscriber. A property that participates in the INotifyPropertyChanged plumbing gets declared like this...
private string _name;
[Description("Name of the driver")]
public string Name
{
[DebuggerStepThrough]
get { return _name; }
[DebuggerStepThrough]
set
{
if (value != _name)
{
_name = value;
OnPropertyChanged("Name");
}
}
}
This code publishes changes, but can also subscribe to changes made on the user surface by setting the appropriate attributes in your Xaml.
Background reading: What is a CollectionView?
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