I made a main window that displays various user controls in a content control. In this window, I have the user controls and their accompanying view models in the XAML as DataTemplate Resources. This window has a button that needs to display the user control in the contentcontrol and instantiate the view model for it. How can i pass the resource to my RelayCommand, so that i can tell the command which user control and view model to use? I figured out how to pass a hard-coded string as the command parameter, but now I'm wanting to pass the x:Name so i can reuse this command etc for more than one View-ViewModel.
Main Window's XAML snippets:
<Window.Resources>
<!--User Controls and Accompanying View Models-->
<DataTemplate DataType="{x:Type EmployerSetupVM:EmployerSetupVM}" x:Key="EmployerSetup" x:Name="EmployerSetup">
<EmployerSetupView:EmployerSetupView />
</DataTemplate>
<DataTemplate DataType="{x:Type VendorSetupVM:VendorSetupVM}">
<VendorSetupView:VendorSetupView />
</DataTemplate>
</Window.Resources>
<Button Style="{StaticResource LinkButton}" Command="{Binding ShowCommand}" CommandParameter="{StaticResource EmployerSetup}">
...
In the Main Window's ViewModel, here relevant code so far:
public RelayCommand<DataTemplate> ShowCommand
{
get;
private set;
}
ShowCommand = new RelayCommand<string>((s) => ShowExecuted(s));
private void ShowExecuted(DataTemplate s)
{
var fred = (s.DataType); //how do i get the actual name here, i see it when i hover with intellisense, but i can't access it!
if (!PageViewModels.Contains(EmployerSetupVM))
{
EmployerSetupVM = new EmployerSetupVM();
PageViewModels.Add(EmployerSetupVM);
}
int i = PageViewModels.IndexOf(EmployerSetupVM);
ChangeViewModel(PageViewModels[i]);
}
...
in other words, how do i get the name of the my DataTemplate w/ x:Key="EmployerSetup" in the XAML? If it matters, I'm using MVVMLight too
Try using the Name property of the class Type:
private void ShowExecuted(DataTemplate s) {
var typeName = s.DataType as Type;
if (typeName == null)
return;
var className = typeName.Name; // className will be EmployerSetupVM or VendorSetupVM
...
}
I'd still say passing the DataTemplate to the VM just seems strange. I'd just have two commands and switch the command used in the Button.Style according to the conditions you got.
If you "have" to use a single RelayCommand or the world might end, I'd tend to use a static enum that you can reference from xaml for CommandParameter than pass the whole DataTemplate object.
Related
I'm writing WPF application with MVVM structure using MVVM Light.
I have class Foo in the Model:
class Foo: ObservableObject
{
private string _propA = String.Empty;
public string PropA
{
get => _propA ;
set
{
if (_propA == value)
{
return;
}
_propA = value;
RaisePropertyChanged("PropA");
}
}
// same for property PropB, PropC, PropD, etc.
}
And I have some collection of Foo objects in the Model:
class FooCollection: ObservableObject
{
private ObservableCollection<Foo> _items = null;
public IEnumerable<Foo> Items
{
get { ... }
set { ... }
}
public string Name { get; set; }
// ...
// and other methods, properties and fields
}
Now I have a ViewModel where this list is populated via some injected provider:
class MainWindowModel: ViewModelBase
{
private FooCollection _fooList;
public FooList
{
get => _fooList;
set
{
_fooList = value;
RaisePropertyChangedEvent(FooList);
}
}
public MainWindowModel(IFooListProvider provider)
{
FooList = provider.GetFooList();
}
}
And the View, with MainWindowModel as data context:
<TextBlock Text={Binding FooList.Name} />
<ItemsControl ItemsSource="{Binding FooList.Items}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<TextBlock Text={Binding PropA} />
<Button Content={Binding PropB} />
<!-- other controls with bindings -->
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
Everything works fine, I can delete and add new items, edit them and etc. All changes in View reflects automatically in ViewModel and Model via bindings and observable objects, and vice versa.
But now I need to add ToggleButton to data template of ItemsControl, which controls visibility of particular item in other part of window. I need IsChecked value in ViewModel, because control in other part of window is Windows Forms control and I can't bind IsChecked directly without ViewModel.
But I don't want to add new property (Visibility, for example) in model classes (Foo, FooCollection), because it is just an interface thing and it doesn't need to be saved or passed somewhere outside ViewModel.
So my question: what is the best way to add new property to Model collection in ViewModel?
I could create new collection of wrappers in ViewModel (some sort of class Wrapper { Foo item, bool Visibility }) and bind it to ItemsControl. But in this case I have to control adding, removing and editing manually and transfer all changes from List<Wrapper> to FooList.Items, so I don't like this solution. Is there any more simple way to achieve this?
Edition to clarify the question. Now I have:
<ItemsControl ItemsSource="{Binding FooList.Items}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<TextBlock Text={Binding PropA} />
<Button Content={Binding PropB} />
<ToggleButton IsChecked={Binding ????????????} />
<!-- other controls with bindings -->
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
I have no field in class to bind IsChecked and I don't want to add it to class, because it's only interface thing and not data model field. How can I, for example, create another collection of bools and bind it to this ItemControl alongside with FooList.Items?
The best place to add the property is of course in the Foo class.
Creating another collection of some other type, add an object per Foo object in the current collection to this one, and then bind to some property of this new object seems like a really bad solution compared to simply adding a property to your current class.
Foo is not an "interface thing", or at least it shouldn't be. It is view model that is supposed to contain properties that the view binds to. There is nothing wrong with adding an IsChecked property to it. This certainly sounds like the best solution in your case.
I'm not sure if I understand why you would need to add a property in the model.
Can't you just use the command property or add an EventTrigger to your toggle button?
(See Sega and Arseny answer for both examples Executing a command on Checkbox.Checked or Unchecked )
This way, when you check the toggleButton, there is a method in your viewModel which enable or disable the visibility property of your Winform control.
To change the visibility of your control from a command in your viewModel, you could use the messenger functionnality of MVVM LIGHT
MVVM Light Messenger - Sending and Registering Objects
The ViewModel sends a message to you're Windows Forms and this one handles the visibility of your control.
First of all, I'm newbie in WPF and specially in MVVM. I have a window with diferent tabs and a very large ViewModel with the business logic of the content of every tab. I know it is not right, so now I'm trying to do it more elegant:
As I see googling, an idea is to do a collection of a "base" viewmodel from wich inherit the sub-viewmodels of every tab, and a collection on this "base" viewmodel in the viewmodel of the window.
TabBaseViewModel
Tab1ViewModel inherits TabBaseViewModel
Tab2ViewModel inherits TabBaseViewModel
MainWindow ViewModel --> Collection of TabBaseViewModel
The contents the tabs do not have anything in common along each other.
How I have to proceed?
You should consider using an MVVM framework if you're using MVVM. With Caliburn.Micro for example, you can define your main view as:
<TabControl x:Name="Items">
<TabControl.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding DisplayName}" />
</DataTemplate>
</TabControl.ItemTemplate>
</TabControl>
Where the data context is a Conductor type that has a collection. The Items property will expose a collection of your view models:
public class MainViewModel : Conductor<IScreen>.Collection.OneActive
{
private OneOfMyViewModels oneOfMyViewModels;
private AnotherViewModel anotherViewModel;
protected override void OnInitialise()
{
// Better to use constructor injection here
this.oneOfMyViewModels = new OneOfMyViewModels();
this.anotherViewModel = new AnotherViewModel();
this.Items.Add(this.oneOfMyViewModels);
this.Items.Add(this.anotherViewModel);
}
protected override void OnActivate()
{
base.OnActivate();
this.ActivateItem(this.oneOfMyViewModels);
}
}
public class OneOfMyViewModels : Screen
{
public OneOfMyViewModels()
{
this.DisplayName = "My First Screen";
}
}
I posted an answer to a different question which shows how to do exactly this: How to Get a Reference to a ViewModel
It's a very simple example, but hopefully should get you started along the right track.
I have a custom UserControl called SongDescription:
<UserControl x:Class="DPTestAp.SongDescription" ...>
<Grid x:Name="LayoutRoot">
<DockPanel Height="50">
<TextBlock x:Name="title" Text="{Binding name}" Width="100" Height="30"/>
<TextBox x:Name="lyrics"/>
</DockPanel>
</Grid>
</UserControl>
I added DependencyProperty to it:
public partial class SongDescription : UserControl
{
public static readonly DependencyProperty SongProperty = DependencyProperty.Register("Song", typeof(Song), typeof(SongDescription));
public Song Song
{
get
{
return (Song)GetValue(SongProperty);
}
set
{
SetValue(SongProperty, value);
updateLyrics()
}
}
private void updateLyrics()
{
lyrics.Text = Song.lyrics;
}
public SongDescription()
{
InitializeComponent();
}
}
The question is: how to bind something to this SongProperty?
I use SongDescription in my main window like this:
<local:SongDescription x:Name="songDescription" Song="{Binding DataContext}"/>
I cannot make my TextBox lyrics show lyrics. In main window I tried to set DataContext to songDescription, like this:
songDescription.DataContext = new Song() { name="Home", lyrics="Hold on, to me as we go" };
or to window itself like this:
DataContext = new Song() { name="Home", lyrics="Hold on, to me as we go" };
I even tried to make Song a resource and bind it to SongProperty like this:
<Window.Resources>
<local:Song x:Key="res" name="Home" lyrics="Hold on, to me as we go"/>
</Window.Resources>
<Grid>
<local:SongDescription x:Name="songDescription" Song="{StaticResource res}"/>
</Grid>
Nothing helped. TextBlock title binds song name fine. But I can't make updateLyrics() method be called. (In real life this method is more complicated, so I can't use Binding like with name).
Thank you!
Yup, so that's a gotcha with dependency properties. You never ever put validation code inside of the accessor methods (get/set) because dependency properties are stored by WPF in a table that it itself manages. This is why you have to register dependency properties, it essentially creates entries on this table for storing the values associated with each property, and when you use 'GetValue' / 'SetValue' you are updating the entries on this table (which by the way relates to how WPF is able to manage data bindings in general).
The upshot of this though is that WPF can (and will) completely bypass your property accessors because it has direct access to the real data. Why should it use your accessors if it can just go to the data directly. Instead you need to implement a 'PropertyChanged' callback function or some WPF sanctioned method of doing validation, but never ever do it in your accessors.
See:
http://msdn.microsoft.com/en-us/library/ms752914.aspx
In addition to sircodesalot's answer, you are not bound on your lyrics textbox. Also, since the song your bound to is a class, you will need to specify the paths fully for the properties you want to show in the boxes such as "Path=Song.Lyrics".
Another thing to consider is that with dependency properties; your mode will be oneway by default so making the text field editable would be moot really unless you change it.
Third, if you're using MVVM you only need your main window context to be set to the view model and have a matching Song property to bind against.
I have several UserControls that should display the same data. Each UserControl has a different layout of the data that is to be presented. The ContentPresenter can bind to any one of the UserControls by using a DataTemplate in my Resources and by binding the Content to a StyleViewModel. Each UserControl is associated with a ViewModel as defined in the DataType of the DataTemplate. The ViewModels associated with any given UserControl all inherit from the StyleViewModel. The UserControls should get their data from a SettingsViewModel. The UserControls appear in the main Window.
The problem is that I can't figure out how to make the data from the SettingsViewModel accessible to the UserControls.
Is it possible to pass a reference to a SettingsViewModel to the constructor of one of these UserControls that are displayed using a ContentPresenter?
Is there another way to easily switch between different views of the data (i.e. my UserControls) without using a ContentPresenter? If so, how would I make the data accessible to the UserControls?
The following is code from my SingleLineViewModel.cs:
public class SingleLineViewModel : StyleViewModel
{
public SingleLineViewModel() { }
}
The other ViewModels are similar. They are essentially empty classes that inherit from StyleViewModel, so that I can bind to a Style property which is of type StyleViewModel in my SettingsViewModel. The StyleViewModel is also an essentially empty class that inherits from ViewModelBase.
The following is code from my Resources.xaml:
<ResourceDictionary <!--other code here-->
xmlns:vm="clr-namespace:MyProject.ViewModel"
<!--other code here-->
<DataTemplate DataType="{x:Type vm:SingleLineViewModel}">
<vw:ucSingleLine/>
</DataTemplate>
<DataTemplate DataType="{x:Type vm:SeparateLinesViewModel}">
<vw:ucSeparateLines/>
</DataTemplate>
<!--other code here-->
</ResourceDictionary>
The following is code from SettingsViewModel.cs:
public class SettingsViewModel : ViewModelBase
{
// other code here
private StyleViewModel _style;
public StyleViewModel Style
{
get { return _style; }
set
{
if (value != _style && value != null)
{
_style = value;
OnPropertyChanged("Style");
}
}
}
// other code here
public SettingsViewModel()
{
_style = new SingleLineViewModel();
}
// other code here
}
The following is code from my MainView.xaml:
<ContentPresenter Name="MainContent" Content="{Binding SettingsVM.Style}"/>
You might find that you are trying to do much at once. Consider how you might test this scenario? Or how would you walk the data in a Debugger to check its state? Good practice recommends that your data is separate from your UI elements. An MVVM pattern such as you are trying to use normally provides the view models to help transition the data from it's simple data into forms that the UI can use.
With that in mind, I would recommend that you try do develop a ViewModel tier that presents all the data without the UI holding it together, i.e. instead of trying to inject the additional SettingsViewModel into your controls you should make your viewmodels hold everything they need.
It looks like you are off to a good start, your SettingsViewModel lets you get hold of a Style, but your style doesn't seem to have any data. So why not pass it in the constructor.
public SettingsViewModel()
{
_style = new SingleLineViewModel(WhatINeedForStyle);
}
I am binding my entities to an edit form in WPF. Within a DataTemplate, I want to be able to set the background color of the root container within a DataTemplate to show it has been changed and these changes have not yet been submitted to the database.
Here's a very simple sample that demonstrates what I'm talking about (forgive errors):
<Page ...>
<Page.DataContext>
<vm:MyPageViewModel /> <!-- Holds reference to the DataContext -->
</Page.DataContext>
<ItemsControl
ItemsSource = {Binding Items}>
<ItemsControl.Resources>
<DataTemplate
DataType="Lol.Models.Item"> <!-- Item is L2S entity -->
<!-- In real life, I use styles to set the background color -->
<TextBlock Text="{Binding IsDirty, StringFormat='Am I dirty? /{0/}'}"/>
</DataTemplate>
</ItemsControl.Resources>
</ItemsControl>
</Page>
The example just prints out "Am I dirty? yes" or "Am I dirty? no", but you get the idea.
To do this, I'll need to add a public property to my Item (partial class, simple) that can determine if the entity is dirty or not. This is the tough bit.
public partial class Item
{
public bool IsDirty
{
get
{
throw new NotImplementedException("hurf durf");
}
}
}
Outside of the entity, it's pretty simple (as long as you have the DataContext the entity is attached to). Inside, not so much.
What are my options here?
Edit: I don't think there's one good solution here, so suggestions for workarounds are welcome.
(Okay, similar questions exist, but they are all about how to determine this from outside of the entity itself and use the DataContext the entity is attached to.)
If you are using the dbml generated classes, you should be able to implement a couple of partial methods like this:
public partial class SampleEntity
{
partial void OnCreated()
{
this.IsDirty = true;
}
partial void OnLoaded()
{
this.PropertyChanged += (s, e) => this.IsDirty = true;
this.IsDirty = false;
}
public bool IsDirty { get; private set; }
}