WPF controls have certain properties (UserControl.Resources, UserControl.CommandBindings) that can have items added to them from the XAML of a user control declaration. Example:
<UserControl ... >
<UserControl.CommandBindings>
...
</UserControl.CommandBindings>
<UserControl.Resources>
...
</UserControl.Resources>
</UserControl>
I have a new list property defined in my user control:
public partial class ArchetypeControl : UserControl {
...
public List<Object> UICommands { get; set; }
I want to add items to this list like I can with resources and CommandBindings, but when I do this:
<c:ArchetypeControl.UICommands>
</c:ArchetypeControl.UICommands>
I get the error "Error 4 The attachable property 'UICommands' was not found in type 'ArchetypeControl'. "
Suggestions?
-
Given the comments, I've created a test control to show the entire code and reproduce the problem. I'm using visual studio 2010.
<UserControl x:Class="ArchetypesUI.TestControl"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:c="clr-namespace:ArchetypesUI"
mc:Ignorable="d"
d:DesignHeight="300" d:DesignWidth="300">
<c:TestControl.TestObject>
</c:TestControl.TestObject>
<Grid>
</Grid>
</UserControl>
-
namespace ArchetypesUI
{
/// <summary>
/// Interaction logic for TestControl.xaml
/// </summary>
public partial class TestControl : UserControl
{
public Object TestObject { get; set; }
public TestControl()
{
InitializeComponent();
}
}
}
Now the error I get is "Error 2 The attached property 'TestControl.TestObject' is not defined on 'UserControl' or one of its base classes."
Take a look at your XAML:
<UserControl>
^^^^^^^^^^^
<c:TestControl.TestObject>
^^^^^^^^^^^
</c:TestControl.TestObject>
</UserControl>
Here, you are declaring a UserControl, and then trying to set a TestControl property on it. Since UserControl doesn't have the TestControl.TestObject property, WPF that it can't set that property on the UserControl object. You may say, "But I'm declaring a UserControl of type TestControl. My UserControl is a TestControl!" But that's not quite the case. The above declaration is declaring the TestControl class: it's not creating an instance of TestControl, so it can't have instance properties set on it.
Rather, the TestObject property is there for users of TestControl to set on individual instances of TestControl:
<local:TestControl>
<local:TestControl.TestObject> <!-- Now it will work -->
</local:TestControl.TestObject>
</local:TestControl>
If you want to set a default / initial value for the TestObject property, then you can do so either in the TestControl constructor, or (if TestObject is a dependency property) through the TestControl default style (though this is more for custom controls than for user controls).
I'm not quite able to recreate your issue... the case I've created seems to work. I did have to initialize the list in the constructor.
However, from your example I wonder a more appropriate place for your list source would be on a ViewModel object of some sort. If you're exposing commands, having an IEnumerable of some sort of a ICommand wrapper which also encapsulates the display elements you need (e.g. Caption, Icon URI, etc).
ViewModels are certainly not a panacea, but in this case I think it would let you put all the knowledge of the commands you want to use in the same place (e.g. which are available and what they do).
Related
Okay, i have to ask this question. I searched a lot but i have 2 problems, and i only find solutions so solfe one of it, but never both.
so what do i have:
i have a UserControl
<UserControl
x:Class="Project.UserControls.UserDetailsControl"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:prism="http://www.codeplex.com/prism"
d:DesignHeight="450"
d:DesignWidth="800"
prism:ViewModelLocator.AutoWireViewModel="True"
mc:Ignorable="d">Some Controls in here</UserControl>
as you see, i am using prism. and i use also Dependency Injection with prism.Dryloc
the Code Behind:
using Project.Assistant.Common.Models;
using Project.GraphQL.Client;
using System.Windows;
using System.Windows.Controls;
namespace Project.Assistant.UserControls;
/// <summary>
/// Interaktionslogik für UserDetailsControl.xaml
/// </summary>
public partial class UserDetailsControl : UserControl
{
public User CurrentUser { get; set; }
public static readonly DependencyProperty SomeNumberProperty= DependencyProperty.Register(nameof(CurrentUser),typeof(User),typeof(UserDetailsControl));
public UserDetailsControl()
{
InitializeComponent();
}
}
These UserControl is then used like a normal Control. And in oder to get the Data into this Control, i Bind the CurrentUser like so:
<controls:UserDetailsControl Grid.Row="1" CurrentUser="{Binding CurrentUser}" />
What do i want to do:
i want to open a new Dialog out of this UserControl.
in order to open a new dialog, i want to use the IDialogService from Prism.
But when i add this to the Contructor, it simply crashes when i want to access the Usercontrol because it cannot Inject this dependency.
problem number too:
if i would simply just use a VieweModel and ViewModelLocator.AutoWireViewModel="True"
i dont know how i could implement my DependencyProperty.
here i read stuff like: "not everything needs a view model" (would solve the DependencyProperty)
and stuff like: "use viewmodels even for Usercontrols" (would solve the dependency injection, but cause problems with DependencyProperty)
what could i do?
I have a custom control which will have properties that can be set which will affect the logic of how the control is handled. How should this be handled in MVVM?
Currently I'm stuck trying to pass a DependencyProperty to the ViewModel.
Example code:
CustomControl.xaml
<UserControl x:Name="Root" ...>
<UserControl.DataContext>
<local:CustomControlViewModel SetDefaultValue="{Binding ElementName=Root, Path=SetDefaultValue, Mode=TwoWay}"/>
</UserControl.DataContext>
...
</UserControl>
CustomControl.xaml.cs
...
public static readonly DependencyProperty SetDefaultValueProperty = DependencyProperty
.Register("SetDefaultValue",
typeof(bool),
typeof(CustomControl),
new FrameworkPropertyMetadata(false));
public string SetDefaultValue
{
get { return (string)GetValue(SetDefaultValueProperty ); }
set { SetValue(SetDefaultValueProperty , value); }
}
...
CustomControlViewModel.cs
...
private bool setDefaultValue;
public bool SetDefaultValue
{
get { return setDefaultValue; }
set
{
if (setDefaultValue!= value)
{
setDefaultValue= value;
OnPropertyChanged("SetDefaultValue"); // INotifyPropertyChanged
}
}
}
...
My goal with this property specifically is to be able to set a default value (getting the default value requires running business logic). So in another view I would use this control like this:
<local:CustomControl SetDefaultValue="True"/>
(Before I answer I want to point out that what you have here is actually a user control, not a custom control. That's not nit-picking on my part; A user control is something derived from the UserControl class and it typically has an associated XAML file. A custom control just derives from the Control class and has no associated XAML file. A custom control requires you set to a control template. Custom controls can be styled. User controls cannot.)
The thing about UserControl is that sometimes we create one assuming one specific DataContext, of one type and then we make all of its XAML bind to that object type. This is good for big, main pages of an application that are not meant to be re-used in too many places
But another approach -- that you have started to do here -- is to give our user controls their own dependency properties. So in this case, why not dispense with the need for this control to have any specific DataContext altogether? This is the first step to making user controls truly re-usable in many places.
Unless this control is huge, there's a good chance that When you are laying out its XAML, it can get everything that XAML needs to bind to in just a few properties. So why not make all those properties into dependency properties and make the control's XAML bind to itself?
Make the class be its own DataContext. Set that property on the root UI element of the control's layout and then every Binding should work well.
To illustrate, I've renamed your control class MyUserControl I've renamed your "SetDefaultValue" property to just be "BoolOption" Let's assume that all it needs to show is a checkbox, representing the bool value and a string label on the checkbox. We can do this with just two dependency properties. (In effect, this entire control is now just a pointless, glorified CheckBox control but please ignore that)
MyUserControl.xaml.cs
public static readonly DependencyProperty BoolOptionProperty =
DependencyProperty.Register(nameof(BoolOption),
typeof(bool),
typeof(MyUserControl),
new FrameworkPropertyMetadata(false));
public string BoolOption
{
get { return (string)GetValue(BoolOptionProperty ); }
set { SetValue(BoolOptionProperty , value); }
}
public static readonly DependencyProperty CheckBoxLabelProperty =
DependencyProperty.Register(nameof(CheckBoxLabel),
typeof(string),
typeof(MyUserControl),
new FrameworkPropertyMetadata(string.Empty));
public string CheckBoxLabel
{
get { return (string)GetValue(CheckBoxLabelProperty ); }
set { SetValue(CheckBoxLabelProperty , value); }
}
// Constructor. Here we set the control to be its own UI's DataContext
public MyUserControl()
{
InitializeComponent();
// Make us be the UI's DataContext. Note that I've set the
// x:Name property root Grid in XAML to be "RootUiElement"
RootUiElement.DataContext = this;
}
MyUserControl.xaml
<UserControl x:Class="MyCompany.MyApp.MyUserControl"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:MyCompany.MyApp.Controls"
x:Name="Root"
d:DesignHeight="450"
d:DesignWidth="800"
d:DataContext="{d:DesignInstance {x:Type local:MyUserControl}}"
mc:Ignorable="d">
<Grid x:Name="RootUiElement">
<CheckBox IsChecked="{Binding BoolOption}"
Content="{Binding CheckBoxLabel"
/>
</Grid>
</UserControl>
Finally you could use the control anywhere you wanted, no matter what your current DataContext is, like this
<local:MyUserControl BoolOption="True" CheckBoxLabel="Is Option A enabled?"/>
<local:MyUserControl BoolOption="False" CheckBoxLabel="Is Option B?"/>
Or even bind it to some other DataContext where you're using it like this. Suppose my current DataContext is a view-model that has a boolean UserBoolOptionC property
<local:MyUserControl BoolOption="{Binding UseBoolOptionC}" "Is Option C enabled?"/>
I'm creating a UserControl in WPF, that is able to work for any object of type IMyNode. Basically, it receives an ObservableCollection through a dependency property, register to it and do some stuff.
In one of my usecase, I use in a control that uses(and need), an ObservableCollection of SomeSpecificNode. SomeSpecificNode is an implementation of IMyNode.
Currently, I've a binding error:
System.Windows.Data Error: 1 : Cannot create default converter to perform 'one-way' conversions between types 'System.Collections.ObjectModel.ObservableCollection`1[SomeSpecificNode]' and 'System.Collections.ObjectModel.ObservableCollection`1[IMyNode]'.
I understand why it happens, it doesn't know how to convert automatically an ObservableCollection<SomeSpecificNode> to ObservableCollection<IMyNode>.
What would be the correct approach to do this?
Using a converter would break the NotifyPropertyChange. Using a ObservableCollection<IMyNode> in my parent ViewModel would not work for the other control in the same page.
Thank you!
Here some pseudo code:
public class SomeSpecificNode: IMyNode{
}
public interface IMyNode{
}
public class ParentViewModel {
public ObservableCollection<SomeSpecificNode> SelectedNodes {get;}=> new ObservableCollection<SomeSpecificNode>()
}
<UserControl x:Class="ParentView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:local="clr-namespace:ch.VibroMeter.Xms.Configurators.Controls.ActionBar"
xmlns:dxb="http://schemas.devexpress.com/winfx/2008/xaml/bars"
mc:Ignorable="d"
d:DesignHeight="450" d:DesignWidth="800">
<UserControl.DataContext>
<ParentViewModel/>
</UserControl.DataContext>
<StackPanel Orientation="Horizontal" Name="RootContainer">
<SomeChildControl Nodes="{Binding SelectedNodes}" /><!-- This binding will fail !-->
</StackPanel
</UserControl>
public partial class ParentView : UserControl
{
public static readonly DependencyProperty NodesProperty = DependencyProperty.Register(
nameof(Nodes), typeof(ObservableCollection<IMyNode>), typeof(ParentView), new PropertyMetadata(default(ObservableCollection<IMyNode>), OnNodesChanged));
private static void OnNodesChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
//...
}
public ObservableCollection<IMyNode> Nodes
{
get { return (ObservableCollection<IMyNode>)GetValue(NodesProperty); }
set { SetValue(NodesProperty, value); }
}
}
You should change the type of the dependency property to a compatible type such as IEnumerable<IMyNode>.
You cannot set an ObservableCollection<IMyNode> property to anything else than an ObservableCollection<IMyNode> or null.
An ObservableCollection<SomeSpecificNode> is not an ObservableCollection<IMyNode> but it is an IEnumerable<IMyNode> assuming that SomeSpecificNode implements IMyNode.
So this compiles just fine;
IEnumerable<IMyNode> collection = new ObservableCollection<SomeSpecificNode>();
But this doesn't:
ObservableCollection<IMyNode> collection = new ObservableCollection<SomeSpecificNode>(); //Cannot implictly convert type...
The difference is that IEnumerable<T> is covariant. Please refer to the docs for more information.
Is it possible to call a custom dependency property in the XAML of the element in which it is defined?
I mean, i have the following simple code for my mainWindow:
Code
public partial class MainWindow : Window
{
public static readonly DependencyProperty SpecialToProperty = DependencyProperty.Register("SpecialTo", typeof(double), typeof(MainWindow));
public MainWindow()
{
InitializeComponent();
}
public double SpecialTo
{
get
{
return (double)GetValue(SpecialToProperty);
}
set
{
SetValue(DoubleAnimation.ToProperty, value);
}
}
}
How can i use that dependency property from the XAML partial code of the MainWindow class?
I mean something like:
<Window x:Class="WpfAnimationTEst.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525"
SpecialTo=200>
I know it can be done using attached dependency properties, but is it the only way? Is it not possible to call a dependency property defined in the code-behind?
Thank you and sorry if the question is some kind of stupid, i'm just learning and trying to understand WPF.
I found the answer after I initially posted a wrong answer:
The problem really lies in circular dependencies if you use andreask's answer. I had to create a BaseClass for all windows:
1) Create a new Window Base Class:
public class BaseWindow : Window {
public BaseWindow() { }
public static readonly DependencyProperty SpecialToProperty = DependencyProperty.Register("SpecialTo", typeof(double), typeof(BaseWindow));
public double SpecialTo {
get {
return (double)GetValue(SpecialToProperty);
}
set {
SetValue(SpecialToProperty, value);
}
}
}
This will be the new baseclass for all your windows.
2) Modify your MainWindow xaml: (Change YOURNAMESPACE (2x) to your namespace name)
<local:BaseWindow x:Class="YOURNAMESPACE.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:YOURNAMESPACE"
Title="MainWindow" Height="350" Width="525" SpecialTo="100">
<Grid>
</Grid>
</local:BaseWindow>
3) And you also need to modify your partial MainWindow.cs:
public partial class MainWindow : BaseWindow {
public MainWindow() {
InitializeComponent();
}
}
That worked for me, however, you will always need to use the extra xaml markup in your window declaration.
I'm answering my own question because there seems to be many ways to solve it correctly. I've upvoted the answers that best helped me, but i can't set any as the correct answer since all are correct.
So i'll just post a conclusion. If you think that i'm mistaken, please post a comment and i will correct my mind.
The main answer to my question is no, it is not possible to directly call a custom dependency property defined at code-behind from its "linked" XAML file. It is mandatory to instantiate the control in which the property is defined to call it.
To me, the best workarrounds to use a custom dependency property in XAML, defined in the code-behind are the posted by #Clemens and #Noel Widmer. This and this
You can use custom dependency properties in XAML, but only if you instantiate the control in XAML. For example, take a customized TextBox element:
public class MyTextBox : TextBox
{
public static readonly DependencyProperty SpecialToProperty = DependencyProperty.Register("SpecialTo", typeof(double), typeof(MyTextBox));
public double SpecialTo
{
get
{
return (double)GetValue(SpecialToProperty);
}
set
{
SetValue(DoubleAnimation.ToProperty, value);
}
}
}
You can of course create an instance of MyTextBox in XAML and assign the SpecialTo property there:
<custom:MyTextBox SpecialTo="1.0" />
In your case, however, you're not instantiating the custom class MainWindow, but you create a new instance of class Window, and the Window class isn't aware of the custom dependency property (the SpecialTo property is not even available in Window, since you declared it within the MainWindow class).
For the dependency property to be recognized, you'd need to instantiate MainWindow directly:
<custom:MainWindow
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525"
SpecialTo=200>
However, this means you need to omit the x:class directive that used to combine XAML and codebehind of your window (otherwise you'd run into circular dependencies), and I'm not sure if this correctly initalizes your window...
Yes, it is possible. Dependency properties are used to bind within XAML. If you want to bind to property defined in the code behind window you need to reference this window as XAML element, i.e. add tag for your main window x:Name="mainWindow", and next in the binding expression refer it as ElementName=mainWindow
Let's say I have a custom control which wraps another control (for example MyCustomButton). I expose a property Content, which wraps the inner control:
public object Content
{
get { return innerControl.Content; }
set { innerControl.Content = value; }
}
In order for a consumer to bind to this property, I need to define a DependencyProperty for it:
public static DependencyProperty ContentProperty = DependencyProperty.Register("Content", typeof (object), typeof (MyCustomButton));
but now I need my property definition to use GetValue/SetValue:
public object Content
{
get { return GetValue(ContentProperty); }
set { SetValue(ContentProperty, value); }
}
so I'm not wrapping the value of the inner control anymore.
I can define PropertyMetadata to handle the PropertyChanged event of the DependencyProperty, but then I need a bunch of plumbing code to keep the values in sync and prevent infinite loopbacks on changed.
UPDATE: I can't just derive from Button because my UserControl has various other concerns.
Is there a better way to do this?
Well, depending on the particulars of why you're wrapping a button with a user control, you could define a custom control that inherits from button. Then, instead of wrapping the button and exposing the wrapped methods and properties that you want, you can simply override methods and properties whose behavior you want to define the custom control. This way, you'll get all of the functionality of button without the need to reinvent the wheel.
Here's a google link that walks you through it (one of the first that I found - there are plenty): http://knol.google.com/k/creating-custom-controls-with-c-net#
If the user control has other concerns, this may not be an option for you, but I'm offering this answer because the only purpose that you've mentioned for it is wrapping the button. I'd personally favor creating a custom control and inheriting rather than a user control and wrapping if the control in question is simply meant to be a more specific kind of wrapped/inherited control (i.e. button in your case).
Edit: In light of updated question...
You could do something along these lines. Here is the XAML of the client of your user control:
<Grid>
<local:MyControl ButtonContent="Click Me!"/>
</Grid>
</Window>
Here is the XAML for the user control itself:
<UserControl x:Class="GuiScratch.MyControl"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:local="clr-namespace:GuiScratch"
mc:Ignorable="d"
d:DesignHeight="300" d:DesignWidth="300">
<Grid>
<StackPanel>
<ContentControl Content="Asdf"/>
<Button Content="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type local:MyControl}},Path=ButtonContent}"/>
</StackPanel>
</Grid>
</UserControl>
And, here is the code behind:
public partial class MyControl : UserControl
{
public static readonly DependencyProperty ButtonContentProperty =
DependencyProperty.Register("ButtonContent", typeof(object), typeof(MyControl),
new FrameworkPropertyMetadata(null, FrameworkPropertyMetadataOptions.AffectsRender));
public object ButtonContent
{
get { return (object)GetValue(ButtonContentProperty); }
set { SetValue(ButtonContentProperty, value); }
}
public MyControl()
{
InitializeComponent();
}
}
So, you don't need to handle the binding at all through code. Your client XAML binds to your dependency property, as does the XAML of the user control itself. In this fashion, they share the dependency property setting. I ran this in my little scratchpad, and the result is (at least my understanding of) what you're looking for. The main window displays the user control as a stack panel with the text "Asdf" and then a button with the text "Click Me!"