I'm trying to implement a ConnectionString dialog, where the user can enter all the values which are necessary to create a valid ConnectionString, e.g. UserID, IntegratedSecurity, etc....
There is also a ComboBox which enlists all the available databases which can be found at this endpoint. This ComboBox should only bind to the ItemsSource, when it is opened and not when the user changes for example the UserID.
Is there a easy way to refresh the ItemsSource values only when the Values are displayed(for example when opening the combobox). The Problem is when the user enters invalid values there is always an exception because the user has not finished entering all the necessary values.
I have already tried to implement this with the event ComboBox_DropDownOpened but I wonder if there is a more practical way to achieve this. I have noticed there is a BindingProperty "UpdateSourceTrigger" but I don't know if I can use it for my problem.
Thanks for any help!
<ComboBox Text="{Binding InitialCatalog}"
SelectedValue="{Binding InitialCatalog}"
ItemsSource="{Binding Databases}" IsEditable="True"/>
If the event ComboBox_DropDownOpened is working you can wrap it in a behavior which should look like this :
internal class ItemsSourceBindingOnOpenBehavior
{
public static readonly DependencyProperty SourceProperty =
DependencyProperty.RegisterAttached("Source", typeof(ObservableCollection<string>),
typeof(ItemsSourceBindingOnOpenBehavior),
new UIPropertyMetadata(null, OnSourceChanged));
public static ObservableCollection<string> GetSource(DependencyObject obj)
{
return (ObservableCollection<string>)obj.GetValue(SourceProperty);
}
public static void SetSource(DependencyObject obj, ObservableCollection<string> value)
{
obj.SetValue(SourceProperty, value);
}
private static void OnSourceChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
SetSource(d);
}
private static void SetSource(DependencyObject d)
{
var cbo = d as ComboBox;
if (cbo != null) cbo.DropDownOpened += (s, a) => { cbo.ItemsSource = GetSource(cbo); };
}
}
To activate the behavior use the two provided attached properties in your XAML :
<ComboBox a:ItemsSourceBindingOnOpenBehavior.Source="{Binding ViewModelCollection}"/>
Related
I'm working with a custom WPF behavior (the one from System.Windows.Interactivity) showing a couple of dependency properties, one of those being a string. The behavior also overrides OnAttached in order to grab a reference to its AssociatedObject UI control.
When that attached property is data-bound to viewModel and is later changed (and notified) at some point, everything seems fine: OnAttached has been fired "at the beginning", and later the PropertyChangedCallback gets fired.
The issue I see is when the property is not bound, but set to a "static" value in XAML. In this case the PropertyChangedCallback gets fired before OnAttached, when the behavior has yet to know its associated UI control and basically cannot do anything in reaction to that property changing.
I guess I'm missing something on how things should be done in this case. Any help in understanding this is appreciated. TA
EDIT
Showing here some code, if that might be helpful in this case:
public class SomeUIControlBehaviour : Behavior<SomeUIControl>
{
protected override void OnAttached()
{
base.OnAttached();
_attachedUIControl = this.AssociatedObject;
}
protected override void OnDetaching()
{
base.OnDetaching();
_attachedUIControl = null;
}
private SomeUIControl _attachedUIControl;
private void MessageChanged()
{
if (_attachedUIControl != null)
{
// do something on it
}
else
{
// bummer!
}
}
// Text property + dependency property
public string Message
{
get { return (string)GetValue(MessageProperty); }
set { SetValue(MessageProperty, value); }
}
private static string _defaultMessage = String.Empty;
// Using a DependencyProperty as the backing store for Message. This enables animation, styling, binding, etc...
public static readonly DependencyProperty MessageProperty =
DependencyProperty.Register("Message",
typeof(string), typeof(SomeUIControlBehaviour),
new PropertyMetadata(_defaultMessage, MessagePropertyChanged));
private static void MessagePropertyChanged(DependencyObject sender, DependencyPropertyChangedEventArgs evt)
{
//Debug.WriteLine("MessagePropertyChanged, on " + sender.GetType().Name + ", to value " + evt.NewValue);
SomeUIControlBehaviour behaviour = sender as SomeUIControlBehaviour;
if (behaviour == null)
{
Debug.Fail("Message property should be used only with SomeUIControlBehaviour");
return;
}
behaviour.MessageChanged();
}
}
As per comment, one simple answer could be:
when behavior gets attached, just check if the property has already a value (maybe different than default) and in that case do what the PropertyChangedCallback was supposed to do.
I'm trying to find a generic way to run an animation each time a property of type double is updated.
This has to be single solution which works for all double values. It means that I don't want to write a proprietory AttachedProperty for each UIElement property (One for Opacity and then another one for Height).
A pseudo-example of what I would like to accomplish:
<TextBlock x:Name="pageTitle" Text="title example" attached:AnimatedPropertyPath="(UIElement.Opacity)" Opacity="{Binding Path=TitleOpacity}" />
The attached property should listen to any change in opacity, cancel it and instead run an animation which makes it change gradually.
My question:
Does this exact syntax make sense? is it doable?
Is there a way to cancel the Opacity property immediate change by the binding and run the animation instead?
Any links to examples would be highly appreciated as I couldn't find any myself.
I want to avoid using DataTriggers because it requires too much xaml. It would be best embedded as an attached property exactly like the peudo xaml above.
My question:
Does this exact syntax make sense? is it doable?
Does it have to be an Attached Property? Would you be fine with using a Behavior?
Is there a way to cancel the Opacity property immediate change by the binding and run the animation instead?
Maybe with some hacks(not that I know of any). Again is this is an absolute must to have to intercept and cancel a normal DP action?
Any links to examples would be highly appreciated as I couldn't find any myself.
Well if you can tweak your requirement slightly, I can give you an example:
So if your requirement is to animate any double DP when it's bound-to value changes, we can do it with a Behavior
public class AnimateBehavior : Behavior<UIElement> {
public static readonly DependencyProperty ToAnimateProperty =
DependencyProperty.Register("ToAnimate", typeof(DependencyProperty),
typeof(AnimateBehavior), new FrameworkPropertyMetadata(null));
public static readonly DependencyProperty ValueProperty =
DependencyProperty.Register("Value", typeof(double),
typeof(AnimateBehavior),
new FrameworkPropertyMetadata(0.0d, FrameworkPropertyMetadataOptions.None, ValueChangedCallback));
public DependencyProperty ToAnimate {
get { return (DependencyProperty) GetValue(ToAnimateProperty); }
set { SetValue(ToAnimateProperty, value); }
}
public double Value {
get { return (double) GetValue(ValueProperty); }
set { SetValue(ValueProperty, value); }
}
private static void ValueChangedCallback(DependencyObject d, DependencyPropertyChangedEventArgs e) {
var item = d as AnimateBehavior;
if (item == null || item.AssociatedObject == null) {
return;
}
var newAnimation = new DoubleAnimation((double) e.NewValue, new Duration(new TimeSpan(0, 0, 1)));
item.AssociatedObject.BeginAnimation(item.ToAnimate, newAnimation);
}
}
Now in xaml:
<TextBlock Text="Hello">
<i:Interaction.Behaviors>
<local:AnimateBehavior ToAnimate="{x:Static TextBlock.OpacityProperty}" Value="{Binding ValueYouWantToBindToOpacity}" />
</i:Interaction.Behaviors>
</TextBlock>
Now with this approach you can animate any DP of that control that has a double type value. Like Opacity, FontSize ...
Main difference here to your original requirement is we do not bind the Value to the element. We instead have it bound to the Behavior. Now when this changes, we detect it in the behavior and via the AssociatedObject property of the behavior, apply the animation on the actual item.
We also satisfy your requirement to satisfy multiple double DP types by providing the property to animate when value changes via a DP to the behavior.
if you want to go even more generic, you can ofc make the Behavior accept a duration and type of animation too to have it even more generic.
Alternate for DP identifying property:
if you absolutely want to pass in "Opacity" and not the DP, then try something like this:
public static readonly DependencyProperty ToAnimateProperty =
DependencyProperty.Register("ToAnimate", typeof(PropertyPath),
typeof(AnimateBehavior), new FrameworkPropertyMetadata(null));
public PropertyPath ToAnimate
{
get { return (PropertyPath)GetValue(ToAnimateProperty); }
set { SetValue(ToAnimateProperty, value); }
}
so we made ToAnimate a PropertyPath
and in the ValueChanged function
private static void ValueChangedCallback(DependencyObject d, DependencyPropertyChangedEventArgs e) {
var item = d as AnimateBehavior;
if (item == null || item.AssociatedObject == null) {
return;
}
var sb = new Storyboard();
var newAnimation = new DoubleAnimation((double) e.NewValue, new Duration(new TimeSpan(0, 0, 1)));
Storyboard.SetTarget(newAnimation, item.AssociatedObject);
Storyboard.SetTargetProperty(newAnimation, item.ToAnimate);
sb.Children.Add(newAnimation);
sb.Begin();
}
we create a Storyboard and use the PropertyPath with this you can have:
<TextBlock Text="Hello">
<i:Interaction.Behaviors>
<local:AnimateBehavior ToAnimate="Opacity" Value="{Binding ValueYouWantToBindToOpacity}" />
</i:Interaction.Behaviors>
</TextBlock>
I'd still prefer the DP over this method.
tl;dr: Coerced values are not propagated across data bindings. How can I force the update across the data binding when code-behind doesn't know the other side of the binding?
I'm using a CoerceValueCallback on a WPF dependency property and I'm stuck at the issue that coerced values don't get propagated through to bindings.
Window1.xaml.cs
using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Media;
namespace CoerceValueTest
{
public class SomeControl : UserControl
{
public SomeControl()
{
StackPanel sp = new StackPanel();
Button bUp = new Button();
bUp.Content = "+";
bUp.Click += delegate(object sender, RoutedEventArgs e) {
Value += 2;
};
Button bDown = new Button();
bDown.Content = "-";
bDown.Click += delegate(object sender, RoutedEventArgs e) {
Value -= 2;
};
TextBlock tbValue = new TextBlock();
tbValue.SetBinding(TextBlock.TextProperty,
new Binding("Value") {
Source = this
});
sp.Children.Add(bUp);
sp.Children.Add(tbValue);
sp.Children.Add(bDown);
this.Content = sp;
}
public static readonly DependencyProperty ValueProperty = DependencyProperty.Register("Value",
typeof(int),
typeof(SomeControl),
new PropertyMetadata(0, ProcessValueChanged, CoerceValue));
private static object CoerceValue(DependencyObject d, object baseValue)
{
if ((int)baseValue % 2 == 0) {
return baseValue;
} else {
return DependencyProperty.UnsetValue;
}
}
private static void ProcessValueChanged(object source, DependencyPropertyChangedEventArgs e)
{
((SomeControl)source).ProcessValueChanged(e);
}
private void ProcessValueChanged(DependencyPropertyChangedEventArgs e)
{
OnValueChanged(EventArgs.Empty);
}
protected virtual void OnValueChanged(EventArgs e)
{
if (e == null) {
throw new ArgumentNullException("e");
}
if (ValueChanged != null) {
ValueChanged(this, e);
}
}
public event EventHandler ValueChanged;
public int Value {
get {
return (int)GetValue(ValueProperty);
}
set {
SetValue(ValueProperty, value);
}
}
}
public class SomeBiggerControl : UserControl
{
public SomeBiggerControl()
{
Border parent = new Border();
parent.BorderThickness = new Thickness(2);
parent.Margin = new Thickness(2);
parent.Padding = new Thickness(3);
parent.BorderBrush = Brushes.DarkRed;
SomeControl ctl = new SomeControl();
ctl.SetBinding(SomeControl.ValueProperty,
new Binding("Value") {
Source = this,
Mode = BindingMode.TwoWay
});
parent.Child = ctl;
this.Content = parent;
}
public static readonly DependencyProperty ValueProperty = DependencyProperty.Register("Value",
typeof(int),
typeof(SomeBiggerControl),
new PropertyMetadata(0));
public int Value {
get {
return (int)GetValue(ValueProperty);
}
set {
SetValue(ValueProperty, value);
}
}
}
public partial class Window1 : Window
{
public Window1()
{
InitializeComponent();
}
}
}
Window1.xaml
<Window x:Class="CoerceValueTest.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="CoerceValueTest" Height="300" Width="300"
xmlns:local="clr-namespace:CoerceValueTest"
>
<StackPanel>
<local:SomeBiggerControl x:Name="sc"/>
<TextBox Text="{Binding Value, ElementName=sc, Mode=TwoWay}" Name="tb"/>
<Button Content=" "/>
</StackPanel>
</Window>
i.e. two user controls, one nested inside the other, and the outer one of those in a window. The inner user control has a Value dependency property that is bound to a Value dependency property of the outer control. In the window, a TextBox.Text property is bound to the Value property of the outer control.
The inner control has a CoerceValueCallback registered with its Value property whose effect is that this Value property can only be assigned even numbers.
Note that this code is simplified for demonstration purposes. The real version doesn't initialize anything in the constructor; the two controls actually have control templates that do everything that's done in the respective constructors here. That is, in the real code, the outer control doesn't know the inner control.
When writing an even number into the text box and changing the focus (e.g. by focusing the dummy button below the text box), both Value properties get duly updated. When writing an odd number into the text box, however, the Value property of the inner control doesn't change, while the Value property of the outer control, as well as the TextBox.Text property, show the odd number.
My question is: How can I force an update in the text box (and ideally also in the outer control's Value property, while we're at it)?
I have found an SO question on the same problem, but doesn't really provide a solution. It alludes to using a property changed event handler to reset the value, but as far as I can see, that would mean duplicating the evaluation code to the outer control ... which is not really viable, as my actual evaluation code relies on some information basically only known (without much effort) to the inner control.
Moreover, this blogpost suggests invoking UpdateTarget on the binding in TextBox.Text in the CoerceValueCallback, but first, as implied above, my inner control cannot possibly have any knowledge about the text box, and second, I would probably have to call UpdateSource first on the binding of the Value property of the inner control. I don't see where to do that, though, as within the CoerceValue method, the coerced value has not yet been set (so it's too early to update the binding), while in the case that the value is reset by CoerceValue, the property value will just remain what it was, hence a property changed callback will not get invoked (as also implied in this discussion).
One possible workaround I had thought of was replacing the dependency property in SomeControl with a conventional property and an INotifyPropertyChanged implementation (so I can manually trigger the PropertyChanged event even if the value has been coerced). However, this would mean that I cannot declare a binding on that property any more, so it's not a really useful solution.
I have been looking for an answer to this rather nasty bug myself for a while.
One way to do it, without the need to force an UpdateTarget on the bindings is this:
Remove your CoerceValue callback.
Shift the logic of the CoerceValue callback into your ProcessValueChanged callback.
Assign your coerced value to your Value property, when applicable (when the number is odd)
You will end up with the ProcessValueChanged callback being hit twice, but your coerced value will end up being effectively pushed to your binding.
Base on your code, your dependency property declaration would become this:
public static readonly DependencyProperty ValueProperty =
DependencyProperty.Register("Value",
typeof(int),
typeof(SomeControl),
new PropertyMetadata(0, ProcessValueChanged, null));
And then, your ProcessValueChanged would become this:
private static void ProcessValueChanged(object source, DependencyPropertyChangedEventArgs e)
{
int baseValue = (int) e.NewValue;
SomeControl someControl = source as SomeControl;
if (baseValue % 2 != 0)
{
someControl.Value = DependencyProperty.UnsetValue;
}
else
{
someControl.ProcessValueChanged(e);
}
}
I slightly modified your logic, to prevent raising the event when the value needs to be coerced. As mentionned before, assigning to someControl.Value the coerced value will cause your ProcessValueChanged to be called twice in a row. Putting the else statement would only raise the events with valid values once.
I hope this helps!
I have a wpf with loads of textboxes and comboboxes etc... And I have a button which allows them to be saved as an xml file. It's not binded or anything, I just serialize it. Now I want to be able to set a boolean if any of the textboxes or comboboxes are modified, so for example, if i close the application it can check the boolean and ask if it needs to be saved or not. I can imagine it's possible by setting this boolean on all events, but there's so many of them, it's crazy to do this.
Is there a better option? Maybe through binding? (not really a pro on binding)
Binding is definitely the preferred choice with WPF. If you use INotifyPropertyChanged, you could create an additional boolean for each property representing each UI elements content.
So, if I had a TextBox bound to property "MyProperty", I would also create a boolean called "IsMyPropertyChanged", and do this:
public bool IsMyPropertyChanged { get; set; }
private string _myProperty;
public string MyProperty
{
get
{
return _myProperty;
}
set
{
if (value != _myProperty)
{
// Update property
_myProperty = value;
NotifyPropertyChanged("MyProperty");
// Set flag
IsMyPropertyChanged = true;
}
}
}
bool TrueExit
private void Window_Closing(object sender, System.ComponentModel.CancelEventArgs e)
{
if (TrueExit)
{
MessageBoxResult result = MessageBox.Show("Save?",
"The End", MessageBoxButton.YesNo, MessageBoxImage.Stop);
if (result == MessageBoxResult.No)
e.Cancel = true;
}
There is a very similar question already posted. In fact, the result of the answer in that post is exactly what I'm after, but I have no codebehind to place that code in. All of our logic is encapsulated in a ViewModel. Since the ViewModel is not supposed to have direct references to specific visual elements, this code cannot exist there either. Is there a way to perform this same thing in XAML somehow, or have I finally ran into a reason to be forced to create codebehind files?
You could try doing something with attached properties..it's a bit elaborate, but it does the same as the other answer, so i think it should work:
public class DependencyPropertyCollection : List<DependencyProperty>
{ }
public static class ValidationUtil
{
public static readonly DependencyProperty ForceValidationProperty =
DependencyProperty.RegisterAttached("ForceValidation", typeof(DependencyPropertyCollection), typeof(ValidationUtil), new PropertyMetadata(OnForceValidationChanged));
private static void OnForceValidationChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
{
FrameworkElement element = (FrameworkElement)sender;
element.Loaded += OnElementLoaded;
}
private static void OnElementLoaded(object sender, RoutedEventArgs e)
{
FrameworkElement element = (FrameworkElement)sender;
element.Loaded -= OnElementLoaded;
foreach (DependencyProperty property in GetForceValidation(element))
element.GetBindingExpression(property).UpdateSource();
}
public static DependencyPropertyCollection GetForceValidation(DependencyObject obj)
{
return (DependencyPropertyCollection)obj.GetValue(ForceValidationProperty);
}
public static void SetForceValidation(DependencyObject obj, DependencyPropertyCollection value)
{
obj.SetValue(ForceValidationProperty, value);
}
}
And you use it like this:
<TextBlock Text="{Binding Text}">
<local:ValidationUtil.ForceValidation>
<local:DependencyPropertyCollection>
<x:StaticExtension Member="TextBlock.TextProperty"/>
</local:DependencyPropertyCollection>
</local:ValidationUtil.ForceValidation>
</TextBlock>
Inside the collection you specify each DependencyProperty which has a binding that you want to validate.