Example:
<UserControl x:Name="userControl"
<StackPanel x:Name="container" Margin="0">
<TextBox Text="{Binding Path=SettingValue, RelativeSource={RelativeSource Mode=Self}}"/>
</StackPanel>
</UserControl>
UserControl contains SettingValue dependency property, TextBox doesn't,
so this example won't work.
I could've done this if I had AncestorType, like in WPF:
RelativeSource Mode=FindAncestor, AncestorType={x:Type UserControlType}
Is there any possibility to bind to UserControl.SettingValue property?
Did you try the following? Use the ElementName source (the syntax might be a bit off).
<TextBox Text="{Binding Path=SettingValue, ElementName=userControl"/>
The answer I've found here:
Binding Silverlight UserControl custom properties to its' elements
Related
I tried to bind a ToolTip text in a UserControl this way:
<Grid.ToolTip>
<TextBlock
Text="{
Binding Path=InfoTT,
RelativeSource={
RelativeSource Mode=FindAncestor,
AncestorType={x:Type UserControl}
}
}" />
</Grid.ToolTip>
And it doesn't work, the Tooltip was empty and in logs, I saw:
System.Windows.Data Error: 4 : Cannot find source for binding with reference 'RelativeSource FindAncestor, AncestorType='System.Windows.Controls.UserControl', AncestorLevel='1''. BindingExpression:Path=InfoTT; DataItem=null; target element is 'TextBlock' (Name=''); target property is 'Text' (type 'String')*
But when I did:
<Grid
ToolTip="{
Binding Path=InfoTT,
RelativeSource={
RelativeSource Mode=FindAncestor,
AncestorType={x:Type UserControl}
}
}">
</Grid>
It worked. Can anyone explain why the first way doesn't work?
When Binding.RelativeSource doesn't resolve, you can always be sure that the Binding.Target is not part of the visual tree.
In your first example you are explicitly defining the tree structure of the ToolTip. You are explicitly creating the content e.g. by adding the TextBlock. The content of the ToolTip is not part of the visual tree and therefore the Binding.RelativeSource can't be resolved.
In your second example, you let the FrameworkElement implicitly create the ToolTip content.
Now FrameWorkElement will first resolve the Binding, which resolves, as the FrameworkElement is still part of the visual tree. The resolved value is taken, ToString invoked, a TextBlock created and the string value assigned to TextBlock.Text.
Solution
To solve the binding problem, when implementing the ToolTip explicitly, you can implement a Binding Proxy as suggested in a comment by #Mark Feldman which makes use of the StaticResource markup to provide a Binding.Source to elements that are not part of the visual tree.
It's basically a bindable ObjectDataProvider.
A similar solution to the binding proxy is to define the content as a resource of the Grid and then reference it via DynamicResource using a ContentPresnter:
<UserControl>
<Grid>
<Grid.Resources>
<!-- The proxy -->
<TextBlock x:Key="ToolTipText"
Text="{Binding RelativeSource={RelativeSource AncestorType=UserControl}, Path=InfoTT}" />
<Grid.ToolTip>
<ToolTip>
<ContentPresenter Content="{DynamicResource ToolTipText}" />
</ToolTip>
</Grid.ToolTip>
</Grid>
</UserControl>
But you could also make use of the fact that the DataContext is still inherited. Bindings to the DataContext will still resolve.
In your scenario, where you want to bind the content of the ToolTip to a property of the parent UserControl, you could bind this property to a property of the view model, which is the current DataContext of Grid (and therefore for its ToolTip). I only recommend this, when binding to business data and not layout data:
<UserControl InfoTT="{Binding ViewModelInfoTT}">
<UserControl.DataContext>
<ViewModel />
</UserControl.DataContext>
<Grid>
<Grid.ToolTip>
<ToolTip>
<TextBlock Text="{Binding ViewModelInfoTT}" />
</ToolTip>
</Grid.ToolTip>
</Grid>
</UserControl>
If you don't use view models and host the data directly in the control, you may like to set the DataContext to the control itself. This way you simplify all bindings and of course can now bind to the UserControl from within the ToolTip:
// Constructor
public MyUserControl()
{
InitializeComponent();
// Set the UserControl's DataContext to the control itself
this.DataContext = this;
}
<UserControl>
<Grid>
<Grid.ToolTip>
<ToolTip>
<TextBlock Text="{Binding InfoTT}" />
</ToolTip>
</Grid.ToolTip>
</Grid>
</UserControl>
Alternatively override the DataContext. Of course you'll lose access to the current context:
<UserControl>
<Grid DataContext="{Binding RelativeSource={RelativeSource AncestoType=UserControl}>
<Grid.ToolTip>
<ToolTip>
<TextBlock Text="{Binding InfoTT}" />
</ToolTip>
</Grid.ToolTip>
</Grid>
</UserControl>
I have User control which contains TextBox with WaterMark inside
<AdornerDecorator>
<TextBox
Height="20"
Margin="10,0"
Grid.Column="0"
Text="{Binding MainCategoryTextBoxValue, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" Name="MainCatTextBox">
<controls:WatermarkService.Watermark>
<TextBlock VerticalAlignment="Center" x:Name="MainCategoryTextBlock"> </TextBlock>
</controls:WatermarkService.Watermark>
</TextBox>
</AdornerDecorator>
You can see here WatermarkService implementation
https://stackoverflow.com/a/836463/1548347
I want take "MainCategoryTextBlock" textblock inside <controls:WatermarkService.Watermark> and set it DataContext to be same like my UserControl DataContext in order to change Watermark text in RunTime from my ViewModel.
I tried to bind "MainCategoryTextBlock" DataContext with RelativeSource to my UserControl DataContext but I didn`t succeed (maybe syntax error - Im not sure).
DataContext="{Binding DataContext, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type UserControl}}}"
Do you have any clue how can I solve it?
Thanks
If your UserControl has a name then you can do it like this:
DataContext={Binding ElementName="YourUserControlName", Path=DataContext}
But i can see that you are using your textbox inside an adorner decorator so you can't use FindAncestor in this case because your textbox and your UserControl won't belong to the same visual tree.
You should be setting the data context property of your window to your view model, and bind the text property of your textblock to your view model property.
<TextBlock Text={Binding Path=PropertyOnViewModel} />
I have created a usercontrol, which has 2 dependency properties. I want to bind those dependency properties to the mainViewModel's property, so that whenever something gets changed in the user-control the parent's property gets updated.
I tried, binding it normally but it didn't work. How can I bind the user-control's DP to the parent's property.
I tried this:
UC:
<TextBox Name="TextBox" Text="{Binding ElementName=UCName, Path=DP1, Mode=TwoWay}"/>
MainWindow:
<UCName:UCName Width="330" CredentialName="{Binding Path=DP1, Mode=TwoWay}"></UCName:UCName>
Thanks
For binding to the parent's properties you should use RelativeSource in your Binding. Like this:
<TextBox Name="TextBox" Text="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type UCName:UCName}}, Path=DP1, Mode=TwoWay}"/>
Details: RelativeSource Markup Extension
Note: Don't forget define namespace UCName.
Something like this:
<MainWindow DataContext="mainViewModel">
<local:TestControl ucDependProp="{Binding viewModelProp}/>
</MainWindow>
className: TestControl.xaml
<UserControl Name="thisControl">
<TextBox Text="{Binding ElementName=thisControl, Path=ucDependProp}/>
</UserControl>
The user control shouldn't be aware of the parent view model.
I'm creating a UserControl I want to use something like this:
<controls:ColorWithText Color="Red" Text="Red color" />
So far, I've implemented similar controls like this:
<UserControl x:Class="Namespace.ColorWithText" Name="ThisControl">
<StackPanel Orientation="Horizontal" >
<Border Width="15" Height="15" Background="{Binding Color, ElementName=ThisControl}" />
<TextBlock Text="{Binding Text, ElementName=ThisControl}" />
</StackPanel>
</UserControl>
where Color and Text are dependency properties of the control defined in code. This works, but specifying ElementName every time seems unnecessary.
Another option that works is using
<UserControl x:Class=… DataContext="{Binding ElementName=ThisControl}" Name="ThisControl">
and not specifying ElementNames, but that doesn't seem like a clean solution to me either.
I have two questions:
Why doesn't <UserControl DataContext="{RelativeSource Self}"> work?
What is the best way to do something like this?
For first one, try :
<UserControl DataContext="{Binding RelativeSource={RelativeSource Self}}">
And for second question, I think using ElementName or AncestorBinding is best way to bind to UserControl's properties.
Why can't you use <UserControl DataContext="{RelativeSource Self}">?
This is how you would use the control
<Grid DataContext="{StaticResource ViewModel}">
<!-- Here we'd expect this control to be bound to -->
<!-- ColorToUse on our ViewModel resource -->
<controls:ColorWithText Color="{Binding ColorToUse}" />
</Grid>
Now because we've hardcoded our data-context in the control it will instead attempt to lookup ColorToUse property on the ColorWithText object not your ViewModel, which will obviously fail.
This is why you can't set the DataContext on the user control. Thanks to Brandur for making me understand that.
What is the best way to do something like this?
Instead you should set the DataContext in the first child UI element in your control.
In your case you want
<StackPanel
DataContext="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type UserControl}}}"
Orientation="Horizontal" >
Now you have a DataContext which refers to your control so you can access any properties of that control using relative bindings.
I know this has been answered but none of the explanations give an Understanding of DataContext and how it works. This link does a great job for that.
EVERYTHING YOU WANTED TO KNOW ABOUT DATABINDING IN WPF, SILVERLIGHT AND WP7 (PART TWO)
In answer to your question #1
Why doesn't <UserControl DataContext="{RelativeSource Self}"> work?
This is a summary of the above link.
DataContext should not be set to Self at UserControl Element level. This is because it breaks the Inheritance of the DataContext. If you do set it to self and you place this control on a Window or another control, it will not inherit the Windows DataContext.
DataContext is inherited to all lower Elements of the XAML and to all the XAML of UserControls unless it is overwritten somewhere. By setting the UserControl DataContext to itself, this overwrites the DataContext and breaks Inheritance. Instead, nest it one Element deep in the XAML, in your case, the StackPanel. Put the DataContext binding here and bind it to the UserControl. This preserves the Inheritance.
See also this link below for a detailed explanation of this.
A SIMPLE PATTERN FOR CREATING RE-USEABLE USERCONTROLS IN WPF / SILVERLIGHT
In answer to your question #2
What is the best way to do something like this?
See code example below.
<UserControl x:Class="Namespace.ColorWithText" Name="ThisControl">
<StackPanel Orientation="Horizontal" DataContext="{Binding ElementName=ThisControl}">
<Border Width="15" Height="15" Background="{Binding Color" />
<TextBlock Text="{Binding Text}" />
</StackPanel>
</UserControl>
Note that once you do this, you will not need the ElementName on each binding.
You should be using
{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type UserControl}}, Path=Color}
for Databinding Related doubts always refer this sheet.
http://www.nbdtech.com/Blog/archive/2009/02/02/wpf-xaml-data-binding-cheat-sheet.aspx
You can set the datacontext to self at the constructor itself.
public ColorWithText()
{
InitializeComponent();
DataContext = this;
}
Now you can simply say
<UserControl x:Class="Namespace.ColorWithText" Name="ThisControl">
<StackPanel Orientation="Horizontal" >
<Border Width="15" Height="15" Background="{Binding Color}" />
<TextBlock Text="{Binding Text}" />
</StackPanel>
</UserControl>
For the desperate souls, who are trying to make pdross's answer work and can't:
It's missing an essential detail - Path=DataContext.
The lower code segment starts working when you add it there with this being the result:
<StackPanel DataContext="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type UserControl}}, Path=DataContext}">
I've got the following user control:
<TabItem
x:Name="Self"
x:Class="App.MyTabItem"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:app="clr-namespace:App"
>
<TabItem.Header>
<!-- This works -->
<TextBlock Text="{Binding ElementName=Self, Path=ShortLabel, UpdateSourceTrigger=PropertyChanged}"/>
</TabItem.Header>
<TabItem.ContentTemplate>
<DataTemplate>
<!-- This binds to "Self" in the surrounding window's namespace -->
<TextBlock Text="{Binding ElementName=Self, Path=ShortLabel, UpdateSourceTrigger=PropertyChanged}"/>
This custom TabItem defines a DependencyProperty 'ShortLabel' to implement an interface. I would like to bind to this and other properties from within the TabItem's DataTemplate. But due to strange interactions, the TextBlock within the DataTemplate gets bound to the parent container of the TabItem, which also is called "Self", but defined in another Xaml file.
Question
Why does the Binding work in the TabItem.Header, but not from within TabItem.ContentTemplate, and how should I proceed to get to the user control's properties from within the DataTemplate?
What I already tried
TemplateBinding: Tries to bind to the ContentPresenter within the guts of the TabItem.
FindAncestor, AncestorType={x:Type TabItem}: Doesn't find the TabItem parent. This doesn't work either, when I specify the MyTabItem type.
ElementName=Self: Tries to bind to a control with that name in the wrong scope (parent container, not TabItem). I think that gives a hint, why this isn't working: the DataTemplate is not created at the point where it is defined in XAML, but apparently by the parent container.
I assume I could replace the whole ControlTemplate to achieve the effect I'm looking for, but since I want to preserve the default look and feel of the TabItem without having to maintain the whole ControlTemplate, I'm very reluctant to do so.
Edit
Meanwhile I have found out that the problem is: TabControls can't have (any) ItemsTemplate (that includes the DisplayMemberPath) if the ItemsSource contains Visuals. There a thread on MSDN Forum explaining why.
Since this seems to be a fundamental issue with WPF's TabControl, I'm closing the question. Thanks for all your help!
What appears to be the problem is that you are using a ContentTemplate without actualy using the content property. The default DataContext for the ContentTemplate's DataTemplate is the Content property of TabItem. However, none of what I said actually explains why the binding doesn't work. Unfortunately I can't give you a definitive answer, but my best guess is that it is due to the fact that the TabControl reuses a ContentPresenter to display the content property for all tab items.
So, in your case I would change the code to look something like this:
<TabItem
x:Class="App.MyTabItem"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:app="clr-namespace:App"
Header="{Binding ShortLabel, RelativeSource={RelativeSource Self}}"
Content="{Binding ShortLabel, RelativeSource={RelativeSource Self}}" />
If ShortLabel is a more complex object and not just a string then you would want to indroduce a ContentTemplate:
<TabItem
x:Class="App.MyTabItem"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:app="clr-namespace:App"
Header="{Binding ShortLabel, RelativeSource={RelativeSource Self}}"
Content="{Binding ComplexShortLabel, RelativeSource={RelativeSource Self}}">
<TabItem.ContentTemplate>
<DataTemplate TargetType="{x:Type ComplexType}">
<TextBlock Text="{Binding Property}" />
</DataTemplate>
</TabItem.ContentTemplate>
</TabItem>
Try this. I'm not sure if it will work or not, but
<TabItem
x:Name="Self"
x:Class="App.MyTabItem"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:app="clr-namespace:App"
>
<TabItem.ContentTemplate>
<DataTemplate>
<TextBlock Text="{Binding Path=ShortLabel}"/>
</DataTemplate>
</TabItem.ContentTemplate>
</TabItem>
If it doesn't work, try sticking this attribute in the <TabItem/>:
DataContext="{Binding RelativeSource={RelativeSource self}}"