I have a custom control (an Adorner) that wraps another control (a textbox).
public class MyCustomAdorner : Decorator
{
...
public MyCustomAdorner()
{
Child = new TextBox();
}
}
I want to be able to override the VisibilityChanged so that the MyCustomAdorner's event is only fired if the Child's visiblity changes, not the actual decorator. How would I go about this?
On a first approach I would try to bind the Adorner's Visibility to the TextBox's Visibility (not sure if this one works). This way, if the textbox changes visibility, the adorner will follow. If you bind them two way, then it will work the other way around too. So if you don't want it to work both ways, make sure you don't set the Adorner's Visibility.
If binding the Visibilities together doesn't work, you can try to declare a new property (for example a bool), that manages the visibilities, and bind the two Visibilities to that bool through a Converter. And when you want to change something around the Visibilities, you set this bool to a new value.
Overriding the VisibilityChange event doesn't sound good to me, also I'm not sure if you can even do that...
Related
When my combobox expands and I select an item, I want the combobox to change visual state(it is highlighted). This will signify something is selected. I tried various VisualStates but none of them would trigger in this scenario. How can I achieve this? Thanks.
The standard ComboBox simply doesn't have states to distinguish between having something selected and having nothing selected.
There are a number of ways to go about solving the underlying problem, and it depends mostly on the answer to the following question:
Do you really need to change the visual appearance of the ComboBox itself or does it suffice to style the selected item more prominently?
If it's the latter, you're best served with the rather easy way of using a custom control template for the ComboBoxItems.
If you really want to style the ComboBox itself that way, there are two options I can think of:
A) Add custom states to a ComboBox with a custom template.
Copy your ComboBox's control template and add another state group to the already present states. Both of this is typically done in Expression Blend.
After that you can update the new states in code with
VisualStateManager.GoToState(this, "Selected", true);
for example. You will have to set those states yourself when the first item is chosen. This could be done on the SelectionChanged event.
B) Derive from ComboBox
If you want to use the control in this way often, it might be worthwhile to derive from ComboBox to make your own custom control.
It would look somthing like this:
[TemplateVisualState(Name = "SelectedStates", GroupName = "Unselected")]
[TemplateVisualState(Name = "SelectedStates", GroupName = "Selected")]
// ... (more attributes copied from the ComboBox ones)
public class MyComboBox : ComboBox
{
public MyComboBox()
{
SelectionChanged += HandleSelectionChanged;
DefaultStyleKey = typeof(MyComboBox);
}
void HandleSelectionChanged(object sender, SelectionChangedEventArgs e)
{
VisualStateManager.GoToState(this, SelectedItem != null ? "Selected" : "Unselected", true);
}
}
And you would then need a default style based on the default ComboBox style (or whatever you usually use).
Note that I didn't test this in any way.
Let me start by saying I am very new to WPF so be gentle.
It seems like this should be easy but I am just missing something. I have implemented INotifyPropertyChanged on a few classes/properties and started binding them to elements in XAML but now I have a little more complex binding to make then updating text or changing a color. What I need is when the Alarm property of my object is set to true I need to change colors, start an animation, create and display other elements in the control. I thought I could just call a function in my control when the property is changed but since WPF hides how an element is "bound" to the model's property I am not sure how to wire that up. Is there a better way to perform this type of more complex response to a property change? If not are there any samples out there? I have not been able to find anything close to what I am looking for but I may not be searching with the correct terms.
What I need is when the Alarm property of my object is set to true I
need to change colors, start an animation, create and display other
elements in the control.
Change colors: Bind the Color/Foreground of the element you want to change the color of, to the boolean that sets the alarm, and add an IValueConverter in the binding that returns a Brush based on the boolean.
Start an animation: Use a (data)trigger on whichever element needs to be animated, in that trigger, use a Storyboard to define the animation you want.
create and display other elements in the control: that really depends on how well you did your MVVM, if the elements are a visualisation of an ObservableCollection through a ListBox/ListView/ItemsControl (which it should), wire up a Command to whatever sets the alarm on/off (the Button class has a Command property built in, other UIElements may require the use of System.Windows.Interactivity) and in the method that this Command will point to, add a new item to the ObservableCollection, the ItemsControl will automatically reflect the change by adding a new control.
Of course this is just raw information, and you're probably not familiar will all these things, that's when Google comes into play ;)
HTH,
Bab.
For complex behaviour in response to a property changed event, you should use the following approach: (I'm typing this freestyle so pardon any minor syntax errors)
class MyClass : INotifyPropertyChanged
{
//Presumably you've already done this part
private object _myProperty = null;
public object MyProperty
{
get { return _myProperty; }
set
{
_myProperty = value;
NotifyPropertyChanged("MyProperty");
}
}
public MyClass()
{
this.PropertyChanged += My_PropertyChanged;
}
private void My_PropertyChanged( object sender, PropertyChangedEventArgs e)
{
if( e.PropertyName == "MyProperty" )
{
//Do Something complicated
}
}
Your timer / alarm just needs to update the bound property when it elapses. The property should then raise the PropertyChanged event to notify the GUI to update.
You should take a look at DataTriggers that get fired when a property changes in the view model. The EnterActions and ExitActions will allow you to play a Storyboard when the value of the property changes. Here's an example of how it is used MSDN. You can use a content control and style the Template or ContentTemplate to add all of your elements and have it control the Visibility or Opacity of the other elements.
I don't think you are looking at this right. Your class has logic, does calculation, enforces constraints, and enforces relationships among properties. If you have an alarm hopefully there is some business logic to deal with this and should be done in the class (not the UI). A UI is not built to handle an alarm it is built to display status and actions of that alarm. You will make new control visible in an alarm situation and hide other. On the animation I think you might want to throw an event that you listen for to start the animation. The idea there is that when an alarm is thrown to can register additional handles - you want to separate the business logic from the UI (not pull the business logic into the UI).
Looking through the standard WPF commands, such as copy/paste, they seem to all work using one button and act on a textbox.
My question: how do I use commands when I have one button, but I need data to be set in two separate controls(a textbox and a combobox). If the user has written text in textbox, but not selected a combobox value, then CanExecute should fail. This applies if combobox has been set, but not the textbox.
In my case specifically, all these controls are wrapped in a tabitem. As well, I have another tab with only a textbox and a button. I want it to have the same functionality as the first tab, except, instead of checking for the combobox value, it should detect that there is no combobox and pass in a default 'null object' value instead.
The Execute method should call a method in my viewmodel and pass in values from the combobox and textbox. As well, each tab should pass in another unique static value; i think i can handle this using commandparameter though.
How do I make this work? Do I make the parent tab that commandtarget and directly reference its children controls in the can/execute methods?
You need to implement CanExecute method that checks both TextBox databinding value and ComboBox.SelectedItem databinding value.
Take example from your question.
Your TextBox.Text should be databinding to your ViewModel
And as well as your ComboBox.
So your ViewModel should have two Properties:
public string TextBoxCurrentText {get { ...}set {...}}
public string ComboBoxCurrentSelected {get { ...}set {...}}
Then in both Setter, you would do your YourCommmand.RaiseCanExecuteChanged();
So it will execute your CanExecute code piece to determines can your Button be click.
Which can be:
bool YourCommandCanExecute()
{
//Just example
if (!string.IsNullOrEmpty(TextBoxCurrentText) && !string.IsNullOrEmpty(ComboBoxCurrentSelected))
return true;
return false;
}
I'm having one hell of a time trying to get my databinding to work correctly. I have reason to believe that what I'm trying to accomplish can't be done, but we'll see what answers I get.
I've got a UserControl. This UserControl contains nothing more than a button. Now within the code behind, I've got a property name IsBookmarked. When IsBookmarked is set, code is run that animates the look of the button. The idea is that you click the button and it visually changes. We'll call this UserControl a Bookmark control.
Now I have another control, which we'll call the FormControl. My FormControl contains a child Bookmark control. I've tried to do databinding on my Bookmark control, but it's not working. Here's some code to help you out.
This is the XAML and Loaded event handler of my control. As you can see it contains a child element that is a custom control (bookmark). So once this control loads, it's DataContext is set to an new instance of an Employee object. Silverlight also sets the DataContext property of my child bookmark control to the same instance. I've verified this by debugging. If my parent has a valid DataContext set then why can't my child control (bookmark) property databind to it?
<UserControl ......>
<q:Bookmark x:Name="BookMarkControl1" IsBookmarked="{Binding IsSiteBookmarked}" />
</UserControl>
public void Control_Loaded(object sender, EventArgs e)
{
DataContext = new Employee { IsSiteBookmarked = True };
}
This is my custom control below. Obviously it contains more than this, but for readability I've trimmed it down to the property I'm trying to databind to.
//this is the bookmark control. I've included this control within another control, and I'm trying to databind to properties within my parents DataContext
public partial class Bookmark : UserControl
{
bool _IsBookmarked= false;
public bool IsBookmarked
{
get {return _IsBookmarked;}
set {
_IsBookmarked= value;
SwitchMode(value);
}
}
}
UPDATE
Got some javascript errors that I should mention. Firebug reports a AG_E_PARSER_BAD_PROPERTY_VALUE exception. It doesn't seem like my databinding is even working yet.
Make your IsBookmarked property on the Bookmark control a dependency property.
I presume Control_Loaded is a part of your FormControl, in which case I'm not sure you are using DataContext properly. Best double check that.
UPDATE: Yes, you are using the DataContext properly. AG_E_PARSER_BAD_PROPERTY_VALUE indicates you need to make the IsBookmarked property a dependency property, like so:
Public Property IsBookmarked() As Boolean
Get
Return Me.GetValue(IsBookmarkedProperty)
End Get
Set(ByVal value As Boolean)
Me.SetValue(IsBookmarkedProperty, value)
End Set
End Property
Public Shared ReadOnly IsBookmarkedProperty As DependencyProperty = DependencyProperty.Register("IsBookmarked", GetType(Boolean), GetType(Bookmark), New PropertyMetadata(New PropertyChangedCallback(AddressOf OnIsBookmarkedPropertyChanged)))
Private Shared Sub OnIsBookmarkedPropertyChanged(ByVal d As DependencyObject, ByVal e As DependencyPropertyChangedEventArgs)
Dim cntrl As Bookmark = TryCast(d, Bookmark)
cntrl.SetIsBookmarked(e.NewValue)
End Sub
If you only need to store the value for later use, then you don't need to do anything in the OnIsBookmarkedPropertyChanged procedure, But I put some code there as an example anyway.
Good Luck!
I don't recall the exact order in which databinding is evaluated (and I'm too lazy to go look it up), but as I recall, it initially happens BEFORE the form's Loaded event fires, and without making the IsBookmarked property a dependency property, or at least using INotifyPropertyChanged, it may have trouble establishing the datacontext appropriately. I'd recommend either implementing INotifyPropertyChanged or making IsBookmarked a dependency property. DataBinding is tough enough to get right in the best of circumstances (see my long, bad-tempered rant about it here), and you'll just be making it more difficult on yourself if you aren't setting up your properties in the way that it expects.
The control exposes a IsSiteBookmarked property(which I believe should be a DependencyProperty) but the control is binding to a IsBookmarked which is not shown. Is this intentional? Have you checked your Visual Studio output window for binding errors?
Addition 1:
Since you have fixed the typo in your question and added that there is an error being reported.
Start by clearing up the AG_E_PARSER_BAD_PROPERTY_VALUE problem. Is there a line number and start position in the error message? Start looking there. One strategy is to start taking out XAML until there is no longer an error. This will narrow down the offending code.
Running in debug, mode check for binding errors in the output window.
You might want to also post the Employee class code, especially the IsSiteBookmarked property.
Typically when doing databinding to an object you will want to leverage the INotifyPropertyChanged interface and implement that so that the control can properly invalidate it's property value. Unless you use INotifyPropertyChanged with Mode=TwoWay then any code that changes your DataContext's IsSiteBookmarked will have no effect.
I am following the M-V-VM pattern for my WPF UI. I would like to hook up a command to the TextChanged event of a TextBox to a command that is in my ViewModel class. The only way I can conceive of completing this task is to inherit from the TextBox control, and implement ICommandSource. I can then instruct the command to be fired from the TextChanged event. This seems to be too much work for something which appears to be so simple.
Is there an easier way (than subclassing the TextBox and implementing ICommandSource) to hook up the TextChanged event to my ViewModel class?
First off, you've surely considered two-way data binding to your viewmodel, with an UpdateSourceTrigger of PropertyChanged? That way the property setter of the property you bind to will be called every time the text is changed?
If that's not enough, then I would tackle this problem using Attached Behaviours. On Julian Dominguez’s Blog you'll find an article about how to do something very similar in Silverlight, which should be easily adaptable to WPF.
Basically, in a static class (called, say TextBoxBehaviours) you define an Attached Property called (perhaps) TextChangedCommand of type ICommand. Hook up an OnPropertyChanged handler for that property, and within the handler, check that the property is being set on a TextBox; if it is, add a handler to the TextChanged event on the textbox that will call the command specified in the property.
Then, assuming your viewmodel has been assigned to the DataContext of your View, you would use it like:
<TextBox
x:Name="MyTextBox"
TextBoxBehaviours.TextChangedCommand="{Binding ViewModelTextChangedCommand}" />
Using the event binding and command method might not be the right thing to use.
What exactly will this command do?
You might want to consider using a Databinding to a string field in your VM. This way you can make a call to a command or function from there rather than having the UI care at all.
<TextBox Text="{Binding WorldName}"/>
....
public string WorldName
{
get
{
return WorldData.Name;
}
set
{
WorldData.Name = value;
OnPropertyChanged("WorldName");
// CallYourCustomFunctionHere();
}
}
Can you not just handle the TextChanged event and execute the command from there?
private void _textBox_TextChanged(object sender, EventArgs e)
{
MyCommand.Execute(null);
}
The alternative, as you say, is to create a TextBox that acts as a command source, but that does seem like overkill unless it's something you're planning on sharing and leveraging in many places.