I have a MultiBinding that looks like this:
<MultiBinding Converter="{StaticResource MyConverter}">
<Binding Path="Object1.Object2.MyObject" />
<Binding Path="Object1.Object2.MyCollection[1]" />
<Binding Path="MyBoolean" />
</MultiBinding>
I only want to evaluate this MultiBinding (and thus call MyConverter.Convert()) when MyObject changes. I'm aware that I could set the MultiBinding's UpdateSourceTrigger to Explicit, but considering that Object1 and Object2 are regularly reassigned, I'd have to wire up a lot of PropertyChanged events in the code behind. Is it possible to achieve this in XAML?
Any help would be much appreciated - thanks!
Try setting the DataContext of your hosting control to that of Object2. Then you can bind to MyObject directly. Does this help? Of course, this still means changes to MyCollection and MyBoolean will also trigger the MultiBinding re-evaluation.
It would also help if you provided the context in which you're using your MultiBinding (i.e. is this returning text for a TextBlock?
EDIT:
In response to your comment, perhaps there's a different way. I assume your 3 multi-bound properties have individual PropertyChanged events. If your application allows, perhaps you could move those events out of the MyCollection and MyBoolean properties and into the MyObject property. For example:
public object MyObject
{
get { ... }
set
{
...
OnPropertyChanged("MyObject");
OnPropertyChanged("MyCollection");
OnPropertyChanged("MyBoolean");
}
}
Now I know this is a bit of a hack but this would trigger the MultiBinding only on change of MyObject.
EDIT #2:
Another option would be adding a EventTrigger to the hosting control, for example:
<EventTrigger RoutedEvent="MyObject.TargetUpdated">
<Setter TargetName="yourCheckBox" Property="Value">
<Setter.Binding>
<MultiBinding Converter="{StaticResource MyConverter}">
<Binding Path="MyObject" />
<Binding Path="MyCollection" />
<Binding Path="MyBoolean" />
</MultiBinding>
</Setter.Binding>
</Setter>
</EventTrigger>
Only catch here would be to make sure Mode=TwoWay on your checkbox binding.
I referred to this link.
Related
I have a multilanguage application and I'm trying to set as Fallbackvalue a Dynamic resource in this way:
<TextBlock Text="{Binding SomeProperty, FallbackValue='{DynamicResource somekEY}'" />
this will throw an exception:
You can set 'DynamicResourceExtension' for the 'StringFormat' type 'Binding' property. You can set 'DynamicResourceExtension' only for a DependencyProperty of a DependencyObject.
how can handle this situation?
The issue is that DynamicResource works like a binding. You can't bind properties of Binding itself (or anything that isn't a DependecyProperty as stated in the error message). You actually see the same sort of error message when you try to do that with a binding: (e.g. {Binding SomeProperty, FallbackValue={Binding SomeOtherProperty}})
This is where PriorityBinding comes in. It allows specifying a series of fallback values as bindings themselves. With PriorityBinding you specify a list of Bindings, the first binding with a valid value is the one used. Ideally we could write something like this:
<TextBlock>
<TextBlock.Text>
<PriorityBinding>
<Binding Path="SomeProperty" />
<DynamicResource ResourceKey="somekEY" />
</PriorityBinding>
</TextBlock.Text>
</TextBlock>
Unfortunately, DynamicResourceExtension can't directly be converted to a binding to be used in a PriorityBinding (or MultiBinding) like the above, so we'll have to use a little trick instead (the example above won't work). We'll use the Tag property (which is a property that has no effect and is basically for holding values for tricks like this) to capture the value of the DynamicResource, and then use a RelativeSource binding in the PriorityBinding to get it:
<TextBlock Tag="{DynamicResource somekEY}">
<TextBlock.Text>
<PriorityBinding>
<Binding Path="SomeProperty" />
<Binding Path="Tag" RelativeSource="{RelativeSource Mode=Self}" />
</PriorityBinding>
</TextBlock.Text>
</TextBlock>
I have created an AttachedProperty that has a PropertyChangedCallback function, which does some formatting to a TextBlock. But to perform the formatting, the Tag attribute is needed. The Tag itself is bound to the output of a Multiconverter.
But my problem is, that the FNamePropertChangedCallback is executed before the Tag is bound to the output of the Multibinding. Thus Tag still Null, when FNamePropertyChangedCallback is triggered.
Is there any way to influence the order in which the Attributes are bound?
I need to bind Tag before binding FInlineProperty.
public static readonly DependencyProperty FInlinePropertyProperty =
DependencyProperty.RegisterAttached("FInlineProperty", typeof(string), typeof(MainWindow),
new PropertyMetadata(null, FNamePropertyChangedCallback));
<TextBlock local:MainWindow.FInlineProperty="{Binding Name}" TextWrapping="WrapWithOverflow">
<TextBlock.Tag>
<MultiBinding Converter="{StaticResource TupleConverter}">
<Binding />
<Binding ElementName="Window"/>
</MultiBinding>
</TextBlock.Tag>
</TextBlock>
Btw: Does someone know how to write local:MainWindow.FInlineProperty="{Binding Name}" in long form? I tried <TextBlock.local:MainWindow.FInlinse>...</TextBlock.local:MainWindow.FInlinse>, but the compiler complains about it.
Update 25.Feb.2017:
I did what you suggested and bound everything to my Attached Property.
<TextBlock TextWrapping="WrapWithOverflow" >
<local:MainWindow.FInlineProperty>
<MultiBinding Converter="{StaticResource GroupConverter}">
<Binding />
<Binding ElementName="Window" Path="MySetup" />
</MultiBinding>
</local:MainWindow.FInlineProperty>
</TextBlock>
The problem with this is, that it is working the first time when the ListBoxItem is created. But updating properties from MySetup does not re-trigger FNamePropertyChangedCallback.
MySetup.ColorString = "green"; // this does not retrigger the callback
MySetup = MySetup.Copy(); // this does retrigger the callback
So currently only assigning MySetup a new copy of itself (changing the reference) triggers callback function again.
That was the reason, why I bound the name property explicitly.
MySetup.ColorString would trigger, if I bind to it explicitly, but I need to bind to MySetup to have all data, so the question is, how to force the binding to execute again, when the bound object itself (reference) has not changed, but something inside did change?
What you actually want is binding between your AttachedProperty and TextBlock.Tag property, so that AttachedProperty is set when Tag changes. But since you are also binding to Name, so I suggest to use MultiBinding for your AP using Name and Tag bindings, thus not depending upon Tag at all.
Try to set the Tag property before you set the attached property. This means that you should also set the attached property using element syntax:
<TextBlock TextWrapping="WrapWithOverflow">
<TextBlock.Tag>
<MultiBinding Converter="{StaticResource TupleConverter}">
<Binding />
<Binding ElementName="Window"/>
</MultiBinding>
</TextBlock.Tag>
<local:MainWindow.FInlineProperty>
<Binding Path="Name" />
</local:MainWindow.FInlineProperty>
</TextBlock>
I have a custom Button type and i cannot change the code. This Button has an property called MyArguments which accepts a string of semicolon separated values.
I have a bunch of TextBoxes on the screen for the user to enter some information.
<TextBox Name="TestTextBox1" />
<TextBox Name="TestTextBox2" />
<TextBox Name="TestTextBox3" />
I want my Button to take these three values and supply them to the MyArguments string property.
If there was only a single TextBox i could use the StringFormat option like this:
<MyButton MyArguments="{Binding ElementName=TestTextBox1, Path=Text, StringFormat='Arguments;{0}' }/>
However you cannot use multiple controls with StringFormat.
I tried using MultiBinding but the MyArguments property gives an error 'The attachable property 'MyArguments' was not found in type MyButton'.
<MyButton.MyArguments>
<MultiBinding StringFormat="Arguments;{0};{1}">
<Binding ElementName="TestTextBox1" Path="Text" />
<Binding ElementName="TestTextBox2" Path="Text" />
</MultiBinding>
</MyButton.MyArguments>
I need this done in pure XAML. No code behind.
Any ideas?
You forgot to add the namespace prefix (e.g. local) to the property:
<local:MyButton>
<local:MyButton.MyArguments>
<MultiBinding StringFormat="Arguments;{0};{1}">
<Binding ElementName="TestTextBox1" Path="Text" />
<Binding ElementName="TestTextBox2" Path="Text" />
</MultiBinding>
</local:MyButton.MyArguments>
</local:MyButton>
This sounds like the parser cannot associate the element syntax property with your element instance. I.e. it thinks you are defining an attached property even though it is supposed to be an instance property.
e.g.
<ListBox ItemsSource="{Binding Data}">
<ListView.ItemTemplate>
<!-- Template -->
</ListView.ItemTemplate>
<ListBox>
Are you referencing the same type? It also looks odd how you have no prefix on your button, or did someone actually abuse the system and compile the assembly to use the WPF namespace?
I have a TextBlock with two MultiBindings. I'd like to make a user control out of this, as I need several instances. The only difference amongst the instances is the Name, and that is only needed as a sort of parameter to the MultiBinding.
<TextBlock x:Name="That"><
TextBlock.Foreground>
<MultiBinding Converter="{StaticResource multiValueFgColorConverter}">
<Binding ElementName="That" Path="Name" />
<Binding Path="TimerState" Mode="TwoWay" />
<Binding Path="Which" Mode="TwoWay" />
</MultiBinding>
</TextBlock.Foreground><TextBlock.Opacity>
<MultiBinding Converter="{StaticResource multiValueOpacityConverter}">
<Binding ElementName="That" Path="Name" />
<Binding Path="TimerState" Mode="TwoWay" />
<Binding Path="Which" Mode="TwoWay" />
</MultiBinding>
</TextBlock.Opacity><Bold><Run Text="That"/></Bold>
-- Is there a way to inject the Name in to an instance of the user control?
-- Or, perhaps wrap this user control in another control where it is used, and have the UC inherit the parent's name?
<grid x:Name="That">
<my:UC/> <!-- 'Inherits' "That"? -->
</grid>
-- Alternatively, is there a way to pass a string as a parameter to the MultiBinding? MultiBinding doesn't take ConverterParameters, as far as I know, so it has to be fudged through the Binding (although I am probably unaware of the better way...)
Thanks for any insights --
Within UserControl expose dependency property and within MultiBinding bind to it. Every single instance of UserControl can then assign binding to specific property making multiBinding updated.
As far as inheriting is concerned, you can inherit propertie's value as long as it allows to do so. x:Name is not able to be inherited.
It's been a while since I touched WPF, can't you use Relative source for that ?
See below.
How do I use WPF bindings with RelativeSource?
So the issue is that when I normally bind a single text item to the Text in a TextBlock, the syntax is as follows:
<TextBlock ... Text="{Binding Attributes[StatusDateTime]}" /> //WORKS GREAT!
Now, background is that the DataContext for this part of the app is the output of a 3rd party API. "Attributes" is a collection of KeyValuePair, which is a property of the parent object. StatusDateTime is the key for the value I am returning. The syntax above works just great! So the object would look something like: theDataContextObject.Attributes[StatusDateTime].
BUT, if I need to combine multiple attributes into one TextBlock that's when things get hairy. I have no idea how to access the key from an actual Binding tag:
<TextBlock Grid.Row="0" Grid.ColumnSpan="3" Style="{StaticResource popupText}">
<TextBlock.Text>
<MultiBinding StringFormat="{}{0} at {1}">
<Binding Path="{Attributes[Type]}"/>
<!--<Binding Path="StatusDateTime" />-->
<Binding Path=Attributes[Type]/>
<Binding Path="Type" ElementName="Attributes"/> //the element has no
//name it's just the datacontext
<Binding Path="[StatusDateTime]" />
<Binding Path="Attributes[StatusDateTime]"/>
</MultiBinding>
</TextBlock.Text>
I know the number of examples above does not match the stringformat, I was just pasting examples of my guesses into the multibinding of how to get these values bound.
Apologies if this is a duplicate with another question. I am not sure what to even call this kind of binding where I'm just passing Attributes[StatusDateTime] directly to binding. Keep in mind that Attributes is not the name of an object, it's a property of the object passed to datacontext of the TextBlock's parent control.
So how do I bind to the value of key in the KeyValuePair collection when i have to use a Binding tag inside a MultiBinding?