I have a Control class named MyControl and it has direct bool property AccessDirectProperty and an Object MyControlSettings
public class MyControl : Control
{
public bool AccessDirectProperty
{
get; set;
}
public MyControlSettings ControlSettings
{
get;set;
}
}
Please find the MyControlSettings class details
public class MyControlSettings
{
public bool AccessIndirectProperty
{
get;set;
}
}
Direct property AccessDirectProperty can be accessible from XAML without any error.
<Window>
<Grid>
<local:MyControl AccessDirectProperty="True"/>
</Grid>
</Window>
But I cannot access the property AccessIndirectProperty from the object ControlSettings in XAML. The below code fails to do that.
<Window>
<Grid>
<local:MyControl AccessDirectProperty="True" ControlSettings.AccessIndirectProperty=""/>
</Grid>
</Window>
Can anyone help me on this?
I'm afraid that XAML does not support accessing "nested" properties.
You could, however, make ControlSettings an independent class with attached properties:
public class ControlSettings : DependencyObject
{
public static readonly DependencyProperty AccessIndirectPropertyProperty =
DependencyProperty.RegisterAttached(
"AccessIndirectProperty", typeof(bool), typeof(ControlSettings),
new PropertyMetadata(false));
public static bool GetAccessIndirectProperty(DependencyObject d)
{
return (bool) d.GetValue(AccessIndirectPropertyProperty);
}
public static void SetAccessIndirectProperty(DependencyObject d, bool value)
{
d.SetValue(AccessIndirectPropertyProperty, value);
}
}
Then,
<local:MyControl x:Name="myControl"
AccessDirectProperty="True"
ControlSettings.AccessIndirectProperty="True" />
would set a value which could be accessed via
var p = ControlSettings.GetAccessIndirectProperty(myControl); // yields True
Now, on a technical level, the following is not useful to modify a property of an existing MyControlSettings instance provided through MyControl.ControlSettings. However, if your use case allows creating and assigning an entirely new MyControlSettings instance to MyControl.ControlSettings, you can do so in XAML:
<local:MyControl>
<ControlSettings>
<local:MyControlSettings AccessIndirectProperty="true" />
</ControlSettings>
</local:MyControl>
A side note: The term "ControlSettings" suggest to me that you want to kind of "package" control settings/properties in some kind of MyControlSettings "container". Now, i don't know why and what the motivation for this is, but keep in mind that choosing this approach can make it very hard or even impossible to use data bindings in a meaningful way where such a settings property is supposed to be the binding target. If you want to be able to use individual settings as binding target (like AccessIndirectProperty="{Binding Path=Source}"), i would rather suggest your MyControl exposes those settings individually as DependencyProperties.
Related
I have a data model (not really a view model; it does not directly contain dependency properties, and I want to keep it that way), which structurally looks something like this:
public class Foo
{
public Bar Data { get; set; }
// other properties
}
public class Bar
{
public string Text { get; set; }
// other properties
}
And a custom UserControl that looks somewhat like this:
<MyUserControl ...>
<Grid>
<TextBox Text="{Binding ???}">
</Grid>
</MyUserControl>
The code-behind of the user control contains a reference to an instance of Foo.
How would I go about binding the Text value of the TextBox inside the MyUserControl to the Data.Text property of the Foo object referenced in the control?
Note:
I would like to avoid declaring a bunch of DPs inside the MyUserControl class as Foo references multiple other types, which respectively contain properties with the same name. So to stay consistent in naming the DPs, I would have to prefix every single one with something showing the nested property they belong to.
So far, I have tried attaching DependencyPropertys to my data model using a helper class with static Get/Set methods as follows:
using DP = System.Windows.DependencyProperty;
static class PropertyProvider
{
public static readonly DP TextProperty = DP.RegisterAttached (
"Text",
typeof (string),
typeof (Bar),
new UIPropertyMetadata ("")
);
public static string GetText (DependencyObject obj) => (string)obj.GetValue (TextProperty);
public static void SetText (DependencyObject obj, string value) => obj.SetValue (TextProperty, value);
}
This results in an XAML Binding Failure and also - after some reasearch - seems to be the wrong approach; I understood it thus far, DPs are supposed to be attached to the control instead instead of the data/view model.
That however leaves me questioning how the data from the control is supposed to be written to/read from the context object, if the DP were attached to the control.
Another thing I attempted, was to simply set the Foo instance as the MyUserControl's DataContext, and declaring the binding like this: Text="{Binding Data.Text}", which seemed to work here.
This also resulted in an XAML Binding Failure, because "Text property not found on object of type Foo".
I have a simple class and I want to simply create instances of my class via xaml. But I'm still getting errors like: "'Test' member is not valid because it does not have a qualifying type name."
UserControl1.xaml.cs:
namespace WpfTestApplication1
{
public class UserControl1 : UserControl
{
public string Test { get; set; }
public UserControl1()
{
}
}
}
UserControl1.xaml:
<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:WpfTestApplication1">
<local:UserControl1>
<Setter Property="Test" Value="aaaa" />
</local:UserControl1>
</ResourceDictionary>
Please, help.
The way you have set the Property on your UserControl is not valid. You have set the Content of your UserControl by putting Setter inside the nodes.
First define Test as DependencyProperty if you want it to be binding target and then set it directly on UserControl as
<local:UserControl1 Test="aaaa"/>
Try to use DependencyProperty instead of default property.
As #us3r said...DependencyProperty is what you are looking for.
What you have to do is:
// Dependency Property
public static readonly DependencyProperty TestProperty =
DependencyProperty.Register( "Test", typeof(string),
typeof(UserControl1 ));
// .NET Property wrapper
public string Test
{
get { return GetValue(TestProperty ).; }
set { SetValue(TestProperty , value); }
}
Finally I found it out.
I defined the control in xaml as
<local:UserControl1 x:Key="xxx" Test="aaaa"/>
Without using setter and property statements, just by directly defining the property.
Thanks for help!
I am working on a DependencyProperty for my Avalon dock controller. Here is some sample code which i have currently working on.
Requirement is: Create all dependency properties in one single class and access the property in View. Something like this.
<Button isPaneVisible="true"> or <Button isPaneVisible="{Staticresource path=name, Mode=twoway">
Could you please help me to reslove this issue?
namespace Avatar.UI.ViewModel
{
internal class DependencyPropertyClass : DependencyObject
{
public static readonly DependencyProperty IsPaneVisibleProperty =
DependencyProperty.RegisterAttached("IsPaneVisible", typeof(bool), typeof(DependencyPropertyClass),
new FrameworkPropertyMetadata(true, FrameworkPropertyMetadataOptions.BindsTwoWayByDefault, IsPaneVisible_PropertyChanged));
private static void IsPaneVisible_PropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
}
/// <summary>
/// Sets the IsPaneVisible for an element.
/// </summary>
public bool IsPaneVisible
{
get { return (bool)GetValue(IsPaneVisibleProperty); }
set
{
SetValue(IsPaneVisibleProperty, value);
}
}
}
}
<UserControl x:Class="Avatar.UI.View.ContentView"
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"
mc:Ignorable="d"
xmlns:avalonDock="http://avalondock.codeplex.com"
xmlns:local="clr-namespace:Avatar.UI.ViewModel"
d:DesignHeight="300" d:DesignWidth="300">
<Button IsPaneVisible="true"></Button
</UserControl>
Defining an attached dependency property also requires the definition of static get and set accessor methods. See Custom Attached Properties for more information. Note also that your class does not necessarily need to be derived from DependencyObject as long as it only defines attached properties. But it is always a good idea to define such properties in a public class.
public class DependencyPropertyClass
{
public static readonly DependencyProperty IsPaneVisibleProperty =
DependencyProperty.RegisterAttached("IsPaneVisible", typeof(bool), typeof(DependencyPropertyClass),
new FrameworkPropertyMetadata(true, FrameworkPropertyMetadataOptions.BindsTwoWayByDefault, IsPaneVisible_PropertyChanged));
private static void IsPaneVisible_PropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
}
public static bool GetIsPaneVisible(DependencyObject obj)
{
return (bool)obj.GetValue(IsPaneVisibleProperty);
}
public static void SetIsPaneVisible(DependencyObject obj, bool value)
{
obj.SetValue(IsPaneVisibleProperty, value);
}
}
And as Cyborgx37 has pointed out, you would use an attached property in XAML like this:
<Button local:DependencyPropertyClass.IsPaneVisible="True" />
I could be wrong, but I think you are looking for this:
<Button local:DependencyPropertyClass.IsPaneVisible="true"></Button>
You have to specify the namespace, since IsPaneVisible is not part of the "http://schemas.microsoft.com/winfx/2006/xaml/presentation" namespace.
See: Attached Properties Overview
EDIT
It's been a while since I've done this, so things are slowly coming back to me as I scan your code. For an attached property, you cannot use an instance property to get/set the property. You must create static Get<PropertyName> and Set<PropertyName> functions:
public static void SetIsPaneVisible(DependenyObject target, Boolean value)
{
target.SetValue(IsPaneVisibleProperty, value);
}
public static bool GetIsPaneVisible(DependenyObject target)
{
return (bool)target.GetValue(IsPaneVisibleProperty);
}
Seriously... please read the linked article. It's all explained there.
The dependency property should derive the base calss for which you are going to create dependency property. for example, if you are going to create dependency property for button, then derive the base class button to your class.
This is how I have resolved my issue.
Consider the following Xaml
<Grid>
<TextBox>Text</TextBox>
<Button>Content</Button>
</Grid>
It will set the
Text Property of a TextBox (only WPF)
Content Property of a Button
Children Property of a Grid
But how is this specified? How do you specify which Property that goes between the opening and closing tag in Xaml?
Is this set by some metadata in the Dependency Property or what?
Thanks
There is a ContentPropertyAttribute that is applied to a class. WPF/Silverlight will use reflection to determine which property to use.
If you want to do this with a custom class, you can do it like so:
[ContentProperty("Bar")]
public class Foo : Control
{
public static DependencyProperty BarProperty = DependencyProperty.Register(
"Bar",
typeof(int),
typeof(Foo),
new FrameworkPropertyMetaData(0));
public int Bar
{
get { return (int)GetValue(BarProperty); }
set { SetValue(BarProperty, value); }
}
}
Then you could specify it in XAML like so:
<lcl:Foo>12</lcl:Foo>
Update
Since it is using reflection, you don't really need to do a DependencyProperty. For instance, this will also work:
[ContentProperty("Bar")]
public class Foo : Control
{
public int Bar { get; set; }
}
I'm fairly new to WPF and I have some problems getting databinding to work as I want. I've written a user control which contains a TextBox whose Text-Property I want to bind to a property of my UserControl, which I want to bind again to something else.
What am I missing?
XAML
<!-- User Control -->
<TextBox Text="{Binding Path=TheText}" />
<!-- Window -->
<WpfApplication1:SomeControl TheText="{Binding Path=MyStringProp}" />
C#
// User Control ----
public partial class SomeControl : UserControl
{
public DependencyProperty TheTextProperty = DependencyProperty
.Register("TheText", typeof (string), typeof (SomeControl));
public string TheText
{
get
{
return (string)GetValue(TheTextProperty);
}
set
{
SetValue(TheTextProperty, value);
}
}
public SomeControl()
{
InitializeComponent();
DataContext = this;
}
}
// Window ----
public partial class Window1 : Window
{
private readonly MyClass _myClass;
public Window1()
{
InitializeComponent();
_myClass = new MyClass();
_myClass.MyStringProp = "Hallo Welt";
DataContext = _myClass;
}
}
public class MyClass// : DependencyObject
{
// public static DependencyProperty MyStringPropProperty = DependencyProperty
// .Register("MyStringProp", typeof (string), typeof (MyClass));
public string MyStringProp { get; set; }
// {
// get { return (string)GetValue(MyStringPropProperty); }
// set { SetValue(MyStringPropProperty, value); }
// }
}
Best RegardsOliver Hanappi
PS: I've tried to implement the INotifyPropertyChanged interface on my user control, but it did not help.
You want to bind the Text property of your TextBox back to the TheText property of the UserControl it lives in, right? So you need to tell the binding where the property lives. There's a couple of ways to do this (you can do it with a RelativeSource using FindAncestor) but the easiest way is to give the UserControl a "name" in the XAML and bind using element binding:
<UserControl ...
x:Name="me" />
<TextBox Text="{Binding TheText,ElementName=me}" />
</UserControl>
Now your TextBox will reflect the value you've assigned (or bound) to your "SomeControl.TheText" property - you needn't change any of your other code, although you'll probably want to implement INotifyPropertyChanged on your underlying MyClass object so that the binding knows when the property has changed.
Matt has provided a solution to your problem. Here is a little more explanation and a hint to stop this problem in future.
As SomeControl.DataContext is set in the SomeControl constructor, the window's binding TheText="{Binding Path=MyStringProp}" has a Source of type SomeControl, not MyClass as you intended.
Any bindings that fail at runtime cause debug messages to be logged to the output panel of Visual Studio. In this case, you would have seen that no such property 'MyStringProp' exists on object of type 'SomeControl', which should have raised your suspicions.
I think everyone finds WPF data binding takes some time to learn and especially to debug, but persevere. Data binding in WPF is really fantastic, and I still get a kick out of knowing how easily it makes the data on my UIs stay up to date.