I am attempting to use a Telerik RadDataBoundListBox with a custom ItemTemplate. However, when I attempt to set the DataTemplate I receive an Invalid XAML exception and can no longer compile. Should I be using Styles?
<telerikPrimitives:RadDataBoundListBox Grid.Row="1">
<telerikPrimitives:RadDataBoundListBox.ItemTemplate>
<DataTemplate>
<telerikPrimitives:RadHubTile/>
</DataTemplate>
</telerikPrimitives:RadDataBoundListBox.ItemTemplate>
</telerikPrimitives:RadDataBoundListBox>
This error occurs no matter what is inside the DataTemplate tags.
Related
With the {x:Bind} markup syntax you can bind to events provided the method meets the following requirements:
Match the signature of the event.
OR have no parameters.
OR have the same number of parameters of types that are assignable from the types of the event parameters.
This works perfectly fine outside of a DataTemplate. Once the binding happens inside the DataTemplate the compiler generates the following error:
Xaml Internal Error error WMC9999: Object reference not set to an
instance of an object.
What is the fix for binding to events inside DataTemplates?
Full example code here.
Snippet of the example code below - note the first button (line 2) is fine and the second button (line 6) is also fine. If you comment out line 6 and and comment in line 7, the error occurs.
<StackPanel Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
<Button Tapped="{x:Bind Click}" Content="WORKING"/>
<ListView ItemsSource="{x:Bind Names}">
<ListView.ItemTemplate>
<DataTemplate x:DataType="local:Customer">
<Button Content="{x:Bind Title}"/>
<!--<Button Tapped="{x:Bind Clicky}" Content="{x:Bind Title}"/>-->
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</StackPanel>
I was able to get it to work with the following code:
<DataTemplate x:DataType="local:Customer">
<StackPanel Orientation="Vertical">
<Button Tapped="{x:Bind Clicky}" Content="{x:Bind Title}" />
</StackPanel>
</DataTemplate>
It seems as though you need to have it inside a container for it work. I have no idea why I am guessing magic.
The parser cannot find Clicky from the datacontext of the button while in the template. Because the object that is being handed to the button in the template (from the Names on the ItemSource of the parent) is not the same as outside the template which has a Clicky. You will need to bind Clicky to the page's datacontext to get it to work.
Otherwise turn off any design time operations by setting Tapped="{x:Bind Clicky, IsDesignTimeCreatable=False}.
In the Universal Windows Platform API, how do I use x:Bind inside of a User Control (intended to be the layout for a GridView's ItemTemplate) to bind to instance properties of a GridView's ItemSource?
Background
I'm trying to re-create the layout found in Windows 10 stock apps like Sports, News, Money, etc.
I'm using a two GridViews for the main area of the app; one for "featured articles" (2 large photos w/ headlines) and one for all the other articles (smaller photos w/ headlines).
I'm able to bind to a data source that I supply in the code behind (a List where NewsItem is a POCO with a Image and Headline property) Here's the pertinent parts of the MainPage.xaml:
<Page ...
xmlns:data="using:NewsApp.Models" />
....
<GridView Name="FeaturedItems" Grid.Row="0">
<GridView.ItemTemplate>
<DataTemplate x:DataType="data:NewsItem">
<Grid Name="mainPanel" HorizontalAlignment="Stretch" Width="500" >
<Image Source="{x:Bind Image}" HorizontalAlignment="Stretch" />
<TextBlock Text="{x:Bind Headline}" />
</Grid>
</DataTemplate>
</GridView.ItemTemplate>
</GridView>
....
The Image and Headline bind just fine (even though they've not been styled correctly). However, instead I think I need to bind to a User Control to get the styling options I want, control over resizing esp. when using Visual State Triggers and to simplify the XAML in general (at least, this was the technique suggested to me.)
So, I added a new User Control to the project (FeaturedItemControl.xaml), and copied in the DataTemplate's child Grid:
<UserControl ... >
<Grid Name="mainPanel" HorizontalAlignment="Stretch" Width="500" >
<Image Source="{x:Bind Image}" HorizontalAlignment="Stretch" />
<TextBlock Text="{x:Bind Headline}" />
</Grid>
</UserControl>
And then back in the MainPage.xaml, I change the DataTemplate to reference the new FeaturedItemControl:
<GridView Name="FeaturedItems" Grid.Row="0">
<GridView.ItemTemplate>
<DataTemplate x:DataType="data:NewsItem">
<local:FeaturedItemControl HorizontalAlignment="Stretch" VerticalAlignment="Stretch" />
</DataTemplate>
</GridView.ItemTemplate>
</GridView>
However, I get the error message for both Image and Headline properties: Invalid binding path 'Headline': Property 'Headline' can't be found on type 'FeaturedItemControl'.
I've tried a few things but am flailing just throwing code at the problem without understanding what I'm doing. Any help would be greatly appreciated.
Thank you for your kind attention.
Using Depechie's answer, I formulated this little cheat cheat for posterity:
Do note that you MUST use this technique to utilize the VisualStateManager with items inside your data bound controls' (GridView, ListView) data templates.
1) Create a User Control.
2) Cut the content of the DataTemplate in your page and paste it into the User Control replacing the template's Grid.
3) Reference the User Control from inside the Data Template:
4) Modify the contents of the User Control changing x:Bind statements to utilize object.property notation:
<UserControl>
<StackPanel>
<Image Source="{x:Bind NewsItem.LeadPhoto}" />
<TextBlock Text="{x:Bind NewsItem.Headline}" />
<TextBlock Text="{x:Bind NewsItem.Subhead}" />
</StackPanel>
</UserControl>
5) Add this in the User Control's Code Behind:
public Models.NewsItem NewsItem { get { return this.DataContext as Models.NewsItem; } }
public ContactTemplate()
{
this.InitializeComponent();
this.DataContextChanged += (s, e) => Bindings.Update();
}
Well it's possible to use x:Bind in user controls, but you'll need to add some extra code behind.
I encountered the same problem in my project, you can see the result here : https://github.com/AppCreativity/Kliva/tree/master/src/Kliva/Controls
So what you need to do is, create a property in the code behind of your user control that points to the correct DataContext.
If you do that, you can use properties of that DataContext in the xaml of your control: for example:
Do note that in the constructor of your control you do need to add: DataContextChanged += (sender, args) => this.Bindings.Update(); because the datacontext will change depending on the page where your control is used!
Then on the page where you are placing this control, you'll also need to do the same to enable the x:bind to work.
You'll see this in my example on the MainPage.DeviceFamily-Mobile.xaml and MainPage.xaml.cs files.
Hope this helps.
x:Bind isn't really hierarchical like Binding/DataContext is. Additionally when you're not directly inside a DataTemplate (such as inside your user control) the object that x:Bind tries to use is 'this' rather than 'this.DataContext'. My current line of thinking on how to solve this sort of issue is to try not to use UserControls anywhere. Instead preferring DataTemplates contained within a ResourceDictionary. There are some pretty strong caveats to this approach though, you will for example crash the xaml compiler if you use x:Bind inside a data template that was created from the ResourceDictionary item template (add new item). you can find a pretty complete example here https://github.com/Microsoft/Windows-universal-samples/tree/master/Samples/XamlBind its important to note in the sample where they show the ResourceDictionary being used that its not actually just a ResourceDictionary.xaml its also a ResourceDictionary.xaml.cs (this is where the generated code from x:Bind ends up)
Another option is to add Headline and Image as properties on your user control and x:Bind them from the template, then inside the user control x:Bind as you are currently doing, but now the x:Bind generated path 'this.Headline' will exist. Unfortunately the order things are actually bound means that the x:Bind's you have inside your user control will have to be OneWay rather than the default OneTime. this is because x:Bind OneTime does the bind inside the InitializeComponent call, and any set of properties/DataContext stuff doesn't get done until after that has already run.
So to sum this up, you have two options, use data templates everywhere, or bind to properties that are directly on the user control.
I am trying to design a simple tabbed app using universal windows platform (UWP) using Pivot control.
I have customized header that includes other controls than just a textblock. I am targeting to change color of those controls/graphics on selection of particular PivotItem using triggers in xaml. Default color updates on selection & hover only apply on textblock but not on other controls.
I can try binding color of other controls with forecolor of textblock because I cannot find template binding not control template in UWP xaml. binding with textblock will still give less space for customization as I am targeting AccentColor for header controls/graphics which are defined by MSFT in UAP sdk and we can access them as static resource from generic.xaml. e.g. SystemControlBackgroundAccentBrush. I looked in to xaml triggers as MSFT new xaml architecture allows us to define VisualStateGroups and work using AdaptiveTriggers & StateTrigger. I can't find any other type of triggers like datatriggers, eventtriggers nothing...
<PivotItem>
<PivotItem.Header>
<StackPanel Orientation="Horizontal">
<Path Stretch="Uniform"
Fill="{StaticResource PivotForegroundThemeBrush}"
Width="32pt"
Height="32pt"
Data="M0,33.893959L4.4794149,33.893959 4.4794149,44.677959 48.903614,44.677959 48.903614,33.893959 53.333035,33.893959 53.333035,49.104958 0,49.104958z M24.842734,0L28.513577,0 28.513577,24.615005 35.345016,17.78297 40.346104,17.78297 40.436089,17.883007 26.673088,31.644001 24.072548,29.047991 12.910089,17.883007 13.010208,17.78297 18.001283,17.78297 24.842734,24.615005z"/>
<TextBlock Text="Downloads"
VerticalAlignment="Center" Margin="5"
FontSize="{StaticResource PivotHeaderItemFontSize}"/>
</StackPanel>
</PivotItem.Header>
<Grid></Grid>
</PivotItem>
I have the following code in which I hide a WebView just under the main Grid (LayoutRoot) so I can do a sliding animation later:
<Page...>
<Grid x:Name="LayoutRoot">
...
<Grid x:Name="ContentRoot">
...
</Grid>
<WebView...>
<WebView.RenderTransform>
<CompositeTransform TranslateY="{Binding ElementName=LayoutRoot,
Path=ActualHeight}"/> <!--Does not work-->
</WebView.RenderTransform>
</WebView>
</Grid>
</Page>
When I first type the {Binding ElementName=...} line into the designer, the WebView appears just below the Grid like it should. However, when I rebuild the solution or run the app, the WebView simply obscures the whole LayoutRoot.
This will happen regardless of what I am binding to/whatever the control is; however, binding to the exact same expression will show up properly in the designer and in the phone. To demonstrate what I am saying:
<Button Width="{Binding ElementName=LayoutRoot, Path=ActualHeight}"> <!--Works perfectly, both on designer and phone-->
<Button.RenderTransform>
<CompositeTransform SomeProperty={Binding ElementName=SomeElement, Path=SomePath}"/> <!--This does not work-->
</Button.RenderTransform>
</Button>
Is there any way to bind to LayoutRoot.ActualHeight short of writing C# code for this?
One problem you have is you are trying to bind to ActualHeight which is not a dependency property nor an observable (INotifyPropertyChanged) property, so the binding is only evaluated once when it's first created.
When I bind something to the SelectedItem of a ListView using ElementName, the properties cannot be resolved.
I can still build and run my app, but because of this error I'm not sure that I didn't make any typo's.
I read and tried the answer given in ElementName Binding is failing but Source={x:Reference ...} doesn't seem to exist in the WinRT framework.
Just an example:
My page has a property MyContainerObject with an IEnumerable<MyParentObject> inside called MyParents. Each MyParentObject has an IEnumerable<MyChildObject> called MyChildren inside.
The DataContext of my page:
DataContext="{Binding RelativeSource={RelativeSource Self}}"
I have ListView with the following XAML properties:
x:Name = "FirstListView"
ItemsSource = {Binding MyContainerObject.MyParents}
Then I have another ListView with the following XAML properties:
x:Name = "SecondListView"
ItemsSource = "{Binding SelectedItem.MyChildren, ElementName=FirstListView}"
Now ReSharper gives me the following warning:
Cannot resolve property 'MyChildren' in data context of type 'object'.
Add this to your listview:
d:DataContext="{d:DesignInstance model:MyParentObject}"