I have the following simplified element in a page:
<Grid x:Name="LayoutRoot"
DataContext="{Binding Source={StaticResource MyContext}}"
d:DataContext="{d:DesignData SampleData/MyContextSampleData.xaml}">
The MyContext class has some properties that are references, not just simple data. One such property for that class is public MyReferenceType MyReferenceProperty.
I have built sample data for both MyContext and MyReferenceType.
Here is the MyReferenceTypeSampleData.xaml:
<data:MyReferenceType
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:data="clr-namespace:MyNamespace.Data;assembly=MyNamespace.Data"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
MyValueProperty0="True"
MyValueProperty1="123"
MyValueProperty2="abc"
/>
and MyContextSampleData.xaml is where I am stumped.
<data:MyContext
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:data="clr-namespace:MyNamespace.Data;assembly=MyNamespace.Data"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
MyReferenceProperty="{d:DesignData SampleData/MyReferenceTypeSampleData.xaml}"
/>
MyReferenceProperty="{d:DesignData SampleData/MyReferenceTypeSampleData.xaml}" is of course wrong. I am trying to do the equivalent of what this does for setting d:DataContext. I want the property to be set in the sample data to the sampledata xaml.
Is this possible and if not, what would be the common workaround. Surely this is a typical use case because mock data is rarely just value types. Anyone know how to handle this?
Related
I'm working on a project that uses Prism for its client software. I have a UserControl XAML file that looks something like this:
<UserControl x:Class="UserModule.Frontend.UserListView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:prism="http://prismlibrary.com/"
prism:ViewModelLocator.AutoWireViewModel="True"
mc:Ignorable="d"
d:DesignHeight="450" d:DesignWidth="800">
<Grid>
<ListView ItemsSource="{Binding Users}"/>
</Grid>
</UserControl>
The actual XAML is a bit longer, but my question is:
Rider shows me a warning at the binding of the list view's ItemsSource property. I have a ViewModel that Prism injects correctly and I can see that the list has been populated. However, at design time, I can't see if the property exists, if I don't check for myself. At the same time, I get a warning in the ViewModel class, that the public getter of Users could be removed.
Is there a way to get code completion to recognize the autowired ViewModel with Prism?
You need to define the d:DataContext for your view. And while you're at it, vote for the feature...
Why can't my custom ListView have it's own xaml file? I have a custom Button and it works with a xaml file with no issues, but not my ListView. The main reason I want to use this approach (rather than be forced to create a Style that is place in the Generic.xaml file) is because I would like to take advantage of the Resources element and place all resources related to the listview within the xaml file:
public sealed partial class MyListView : ListView
{
public MyListView()
{
this.InitializeComponent();
}
}
And here is the associated xaml file:
<ListView
x:Class="App1.MyListView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:App1"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
d:DesignHeight="300"
d:DesignWidth="400">
<ListView.Resources>
<!-- I would like to place all related resources here instead of having
them placed in external locations, and then have to open different files to find them. -->
</ListView.Resources>
</ListView>
Although I would expect this should work as well, it seems that this problem is present and it is recommended to use the templated control instead.
I suppose the problem is that assigning the compiler is unable to generate the valid assignment to the Items property of the control, which it is trying to construct from the content of the element. Even when the element is closed immediately it seems to be an issue.
Why not place resources on the Page or inside ListView, rather than deriving your own control?
<Page
x:Class="ListViewResources.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:ListViewResources"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d">
<Page.Resources>
<!-- Place all related resources here instead of having them placed in external locations, and then have to open different files to find them. -->
</Page.Resources>
<ListView x:Name="MyListView">
<ListView.Resources>
<!-- Or place related resources here -->
</ListView.Resources>
</ListView>
</Page>
I'm currently getting started with XAML and I have a question regarding how to define the DataContext of an element.
I've created a View that includes a Page with the following markup:
<Page x:Class="View.MainView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:ViewModel="clr-namespace:ViewModel"
mc:Ignorable="d"
Title="MainView">
...
</Page>
When I want to give this Page a DataContext to be used by child elements, this works:
<Page x:Class="View.MainView"
...
mc:Ignorable="d"
Title="MainView">
<Page.DataContext>
<ViewModel:MainViewModel />
</Page.DataContext>
...
</Page>
And this doesn't:
<Page x:Class="View.MainView"
...
mc:Ignorable="d"
Title="MainView" DataContext="ViewModel:MainViewModel">
...
</Page>
For me, it looks like the Page element expects the DataSource to be defined as a XAML property and not as an attribute. However, the IntelliSense in Visual Studio offers me a DataContext attribute for the Page, so I guess I'm just using a wrong syntax here. Can you point that out to me?
Thanks!
You can use the attribute to specify the DataContext, but you should consider how does your viewmodel get instantiated.
Using a property in this way
<Page.DataContext>
<ViewModel:MainViewModel />
</Page.DataContext>
you tell WPF to instantiate the MainViewModel and to assign the created object to the DataContext property of the Page.
With an attribute, you just specify a string in that case:
DataContext="ViewModel:MainViewModel"
But you want WPF to create an instance for you.
So you can use e.g. a Binding or a StaticResource / DynamicResource to assign a created instance to the DataContext property:
DataContext="{Binding ViewModel}"
or
<Page DataContext="{StaticResource ViewModel}">
<Page.Resources>
<ViewModel:MainViewModel x:Key = "ViewModel"/>
</Page.Resources>
</Page>
Very new to WPF and c# here. I'm interested in having a ComboBox with different color options that will update the window's Background when an option is selected.
I want to do this via DataBinding, but I'm a noob and can't get it right. This is what I have.
MainWindow.xaml
<Window x:Class="WpfApplication1.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525"
Background="{Binding SelectedValue,ElementName=combo,UpdateSourceTrigger=PropertyChanged}">
<StackPanel>
<ComboBox Name="combo">
<ComboBoxItem>lightcoral</ComboBoxItem>
<ComboBoxItem>khaki</ComboBoxItem>
</ComboBox>
</StackPanel>
</Window>
And the default MainWindow.xaml.cs (I haven't touched it since I created the project)
Thanks, let me know if you need any more info!
One possible way to achieve this is to put items of type string in your ComboBox, as opposed to ComboBoxItems:
<Window x:Class="WpfApplication1.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525"
xmlns:sys="clr-namespace:System;assembly=mscorlib"
Background="{Binding SelectedItem, ElementName=combo}">
<ComboBox VerticalAlignment="Center" HorizontalAlignment="Center" x:Name="combo">
<sys:String>Yellow</sys:String>
<sys:String>Green</sys:String>
<sys:String>Red</sys:String>
<sys:String>Blue</sys:String>
</ComboBox>
</Window>
Notice that I declared the xmlns:sys XAML Namespace that points to the System CLR namespace in the mscorlib.dll assembly. This is where the class System.String is defined, and you need that to be able to use the class in XAML.
Also notice that I'm binding to SelectedItem as opposed to SelectedValue, this is because your ComboBox does not have SelectedValuePath, and WPF doesn't have the notion of the SelectedValue because it does not know how to "retrieve the value" from each of it's items.
Also notice that UpdateSourceTrigger is removed because it does not make any sense. UpdateSourceTrigger determines the way the Binding source is updated, not the target. Read about DataBinding on MSDN to understand the terminology here.
The reason that using a String works and using a ComboBoxItem does not is because the default Type Converter for the Brush class (which is the type of the Window's Background) "understands" how to convert from a string, but not from a ComboBoxItem.
I want to make a converter class , I implemented it and i want to use it in another xaml class
So i write this code
<UserControl
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:PoliceApp"
xmlns:common="using:PoliceApp.Common"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d">
<UserControl.Resources>
<local:TitleToImgConverter x:Key="BoolOrConverter"/>
</UserControl.Resources>
</UserControl>
It tells me that there is a missing attribute for user control
and my first code was
DataContext="{Binding DefaultViewModel, RelativeSource={RelativeSource Self}}"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:PoliceApp"
xmlns:common="using:PoliceApp.Common"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d">
<UserControl.Resources>
<local:TitleToImgConverter x:Key="BoolOrConverter"/>
</UserControl.Resources>
And the error was "The name titletoimgconverter doesnt exist in the namespace using:policeApp"
This is normal (at least, I have never seen it otherwise) when you have just created a new converter and added it as a resource in your XAML code. XAML code often lags behind when something is added to the namespace.
The solution for this is to rebuild your entire project. The XAML should now be able to locate your converter, and the error should disappear.
Update
If your converter exists in some folder called Converter, you should use your first example, and replace xmlns:local="using:PoliceApp" with xmlns:local="clr-namespace:PoliceApp.Converter". If it just resides in your main folder, you can leave out the .Converter. Note that I've replaced the using: with clr-namespace:.