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UWP x:bind issue - Invalid binding path 'dpl' : Property 'dpl' not found on type 'DataTemplate'

I have a class PricingData and PricingSchedule. Where PricingSchedule is a List<> inside PricingData class. I want to bind data of this class to UWP controls.
Sample code is available to download here : https://github.com/jigneshdesai/SampleOfBindingIssue1.git
How Code looks: i have a start page(mainpage) that hosts ListView control, Listview has PricingUserControl within it. PricingUserControl looks like this
<TextBlock x:Name="lblPriceHeader" Text="{Binding PricingTitle}" Margin="0,0,50,0" />
<ComboBox x:Name="cbPriceValueList" ItemsSource="{x:Bind dpl}" DisplayMemberPath="PriceValue" SelectedValuePath="PriceValue" SelectedValue="{Binding DisplayPricing}" />
<ListView x:Name="lbPriceChangeSchedule" ItemsSource="{Binding PricingScheduleList}">
<ListView.ItemTemplate>
<DataTemplate>
<StackPanel>
<StackPanel Orientation="Horizontal">
<ComboBox x:Name="cbSchedulePriceValueList" ItemsSource="{x:Bind dpl}" DisplayMemberPath="PriceValue" SelectedValuePath="PriceValue" />
<TextBlock Text="{Binding SchedulePricingTimeZone }" />
</StackPanel>
</StackPanel>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
What i want to achieve: Combobox should populate a list of values (eg. 1USD, 2USD, 3USD etc.). Then when you provide List of records from database, the listbox will repeat PricingUserControl and combobox within it should set its value property (SelectedValue) as per record.
Issue:
ComboBox x:Name="cbPriceValueList" uses x:bind dpl where dpl is a local variable of PricingUserControl. It populates the list properly. The trouble is ComboBox x:Name="cbSchedulePriceValueList" it also has x:bind dpl but during compilation it display error "Invalid binding path 'dpl' : Property 'dpl' not found on type 'DataTemplate'."
I am wondering why x:bind dpl does not work at this point. ?

I have now realized that your problem is in fact that you need to reach to a Page property from within the DataTemplate, so here is a updated answer.
You cannot use x:Bind if you need to access an outside element's property from within a DataTemplate. Instead, you can use classic {Binding} expression. First add a name to your page:
<Page
...
x:Name="Page">
And now refer to this name from within the DataTemplate:
<ComboBox
x:Name="cbSchedulePriceValueList"
ItemsSource="{Binding ElementName=Page, Path=dpl}"
DisplayMemberPath="PriceValue"
SelectedValuePath="PriceValue" />
Original answer
To be able to use x:Bind inside of a DataTemplate, you must specify the data type the individual items of the control will have, using x:DataType. Suppose your PricingScheduleList is a List<MyApp.Models.MyType>, then you will first need to add this XML namespace to the <Page> element:
xmlns:models="using:MyApp.Models"
And then set the x:DataType attribute as follows:
<DataTemplate x:DataType="models:MyType">
...
</DataTemplate>
You can confirm this works by the fact that IntelliSense should now suggest you the properties of MyType when you start writing the x:Bind expression.

By checking your code, the reason why SelectedValue does not take effect is when you choose the item from ComboBox, you didn't notify your DisplayPricing to change. So you need to implement INotifyPropertyChanged interface in your PricingData. Do the same behavior in PricingSchedule.
public class PricingData : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged = delegate { };
......
public string DisplayPricing
{
get => $"{PricingValue} {PricingCurrency}";
set
{
var sp = value.Split(' ');
PricingValue = sp.First();
PricingCurrency = sp.Last();
OnPropertyChanged();
}
}
public void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
PScheduleUserControl.xaml:
<ComboBox x:Name="cbPriceValueList" ItemsSource="{x:Bind myList}" DisplayMemberPath="PriceValue" SelectedValuePath="PriceValue" SelectedValue="{Binding DisplayPricing,Mode=TwoWay}" />

UWP ListView only displays data sometimes

My data from an ObservableCollection only sometimes displays on my ListView. If I restart the app, the data displays fine. Sometimes when I navigate away from the page and go back, the data will sometimes display and other times not. It seems to be random.
Here is my XAML code:
<ScrollViewer Grid.Row="2" Margin="0,42,0,0">
<Grid>
<ListView ItemsSource="{x:Bind collection, Mode=OneWay}" HorizontalAlignment="Left" Margin="0,0,0,0" VerticalAlignment="Top" IsItemClickEnabled="True" SelectionChanged="MySelectionChanged" Visibility="Visible">
<ListView.ItemTemplate>
<DataTemplate x:DataType="local:ObjectName">
<TextBlock Text="{x:Bind Data0, Mode=OneWay}"/>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
<ListView ItemsSource="{x:Bind collection, Mode=OneWay}" HorizontalAlignment="Left" Margin="375,0,0,0" VerticalAlignment="Top" SelectionMode="None" Visibility="Visible">
<ListView.ItemTemplate>
<DataTemplate x:DataType="local:ObjectName">
<TextBlock Text="{x:Bind Data1, Mode=OneWay}"/>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</Grid>
</ScrollViewer>
I tried doing a Debug.WriteLine() on all the data that should be displayed, and the debug output successfully prints it every time. There's only a problem when it comes to displaying this data on the ListView.
EDIT: Here's the corresponding xaml.cs code:
private ObservableCollection<ObjectName> collection;
private List<ObjectName> sorted;
private ObjectName clicked = new ObjectName();
public MainPage()
{
GetSave();
this.InitializeComponent();
}
private async void GetSave()
{
DataStorage ds = new DataStorage();
await ds.DeserializeObjectAsync();
collection = ds.ObjectName;
if (collection != null)
{
sorted = new List<ObjectName>(collection);
sorted.Sort((x, y) => string.Compare(x.Data0, y.Data0));
collection = new ObservableCollection<ObjectName>(sorted);
}
}
I tried InitializeComponent() before and after the logic, and it gives the same result.

Based on the xaml.cs code you provided, the problem looks like this:
First, you are not awaiting an async call.
Second, you are replacing the ObservableCollection.
The solution:
Don't call async code from your page's constructor. Async calls are
called async for a reason and trying to 'hide' their true nature by
omitting the await keyword when calling them won't work. Change GetSave()'s
return value to Task, override the OnNavigatedTo() method (read more
about it in it's documentation) of MainPage and await GetSave()
inside that. This alone won't solve your problem though.
Never replace an ObservableCollection. I remember banging my head on the
wall multiple times because of this. What you need to understand is
that when you are binding to an object in XAML, a dedicated Binding
object is created that links the source (in your case, the
ObservableCollection) and the target (the ListView) together. In
your code, initially 'collection' is set to null. When your MainPage
is created, the Binding object is created as well and it binds that
null value to your ListViews' Source property. Later, when your
async initialzation code is finished, you replace that null value
with an actual ObservableCollection, but the ListViews are not
notified about that, they are only looking for changes in the
collection's items that they are bound to, they are not prepared for
handling the situation when the collection itself is swapped
under them. So what you can do to fix this problem is: only create
your ObservableCollection instance in MainPage's constructor (or at
declaration - matter of taste in this case) and in GetSave() first
call collection.Clear() and then add your items to it with
collection.Add().
What currently happening in your code is that in some cases you are replacing the ObservableCollection before the Binding object is created and sometimes after that, so that's why it looks like you app's behavior is totally random - because actually it is. :) By adding the modifications I suggested above, you'll make sure that the Binding object is bound to the ObservableCollection you created in the constructor (empty at the time of the binding), and then you are initializing that collection after MainPage is already loaded, so your ListViews are getting notified about the changes.

Items collection must be empty before using ItemsSource. Telerik Treeview

Im getting this error while trying to giva my treeview an itemsource
"Items collection must be empty before using ItemsSource."
I have checked a lot of solutions and I cant seem to find a way to solve this. Here are my code snippets:
XAML:
<HierarchicalDataTemplate x:Key="Category">
<TextBlock Text="{Binding Name}">
</TextBlock>
</HierarchicalDataTemplate>
XAML
<telerik:RadTreeView x:Name="treeview" IsDragDropEnabled="True" HorizontalAlignment="Left" Height="250" Margin="10,10,0,-3" VerticalAlignment="Top" Width="190" IsManipulationEnabled="True" IsLoadOnDemandEnabled="True" LoadOnDemand="treeview_LoadOnDemand" IsExpandOnSingleClickEnabled="True" ItemTemplate="{StaticResource Category}">
</telerik:RadTreeView>
C# - Giving the treeview a data source:
Data d = new Data();
treeview.ItemsSource = d.Get_Categories();
C# - My database query:
public List<Category> Get_Categories()
{
using (var context = new ProcessDatabaseEntities())
{
return context.Category.ToList();
}
}
Category only has two properties, Name and ID. I know that the itemsource-list is not empty when I assign it. So it's probably something wrong with my XAML-code. Thank you in advance!

I believe that your problem is a common one. Basically, you cannot use both the TreeView.ItemsSource and the TreeView.Items properties together... you must choose one way or the other. Usually this problem manifests itself because a developer has done something like this...:
<TreeView Name="TreeView" ItemsSource="{Binding SomeCollection}" ... />
... and then tried to do something like this in the code behind:
TreeView.Items.Add(someItem);
The solution in that case would be to manipulate the data bound collection instead of the TreeView.Items collection:
SomeCollection.Add(someItem);
However, in your case (and it's a little bit difficult to guess without seeing your code), you have probably done the second part first (set or manipulated the Items property) and then tried to set the ItemsSource property. Your solution is the same... use one method of editing the items or the other... not both.

Bind a collection to a WPF ListBox

Update: I've updated the code based on your help so far, and still no luck. When the application loads the ListBox has no items. I assign junk values to Customers in the windows's contructor, and then am also trying to set the ListBox's DataContext as follows:
CustomerList.DataContext = Customers;
--- Original Question (with updated code) ---
I'm having trouble with databinding in a WPF project.
I have a class, Customer, as follows:
public class Customer
{
public String Name { get; set; }
public String Email { get; set; }
}
In my XAML's code behind I have a collection of customers as follows:
public List<Customer> Customers { get; set; }
I'm trying to bind each customer to a ListBox with a ListItemTemplate displaying the customer's information (name/email) in TextBoxes along with a button which locks/unloacks the TextBoxes (sets the IsEnabled property to true or false).
What's the best way to go about this?
So far I've been tryingt he following with no success.
In the XAML I currently have the following (ignoring the toggle part for now, I'm just trying to get the collection itself to be listed.):
<Window.Resources>
<CollectionViewSource x:Key="Customers" Source="{Binding Path=Customers, Mode=TwoWay}"/>
<DataTemplate x:Key="Customer">
<StackPanel Orientation="Horizontal">
<TextBox Content="{Binding Name}" />
<TextBox Content="{Binding Email}" />
</StackPanel>
</DataTemplate>
</Window.Resources>
<StackPanel>
<ListBox ItemsSource="{Binding Source={StaticResource Customers}}"
ItemTemplate="{StaticResource ResourceKey=Customer}"
Name="CustomerList"
Height="300" />
</StackPanel>

You need to change
ItemsSource="{Binding Source=Customers}"
to
ItemsSource="{Binding Source={StaticResource Customers}}" DataContext="{StaticResource Customers}"

Code similar to the updated one works for me after changing
<TextBox Content="{Binding Name}" />
to
<TextBox Text="{Binding Name}" />
As TextBox doesn't have Content property(like a Label), the former refused to compile in VS.
Well, it is set to Text in definition:
[ContentPropertyAttribute("Text")]
public class TextBox : TextBoxBase, IAddChild
But I thought it is only used between the brackets(<TextBox>Like so</TextBox>)?
Could this be the source of the problem?

Try setting the ItemsSource of your CustomerList as follows: ItemsSource="{Binding}". You've set the DataContext of the ListBox to the list of customers, you need to set the ItemsSource to the same collection, hence, the direct binding.
Another thing that you can do, in case you prefer to use the CollectionViewSource, is to set the DataContext of your window to the same class DataContext=this, because without this, the resource definition won't be able to locate the "Customers" collection that you defined in the code behind. If you do this, however, you don't need CustomerList.DataContext = Customers; because you're directly assigning the ItemsSource to a static resource, not relatively to the DataContext.
One more thing. I think you should give the CollectionViewSource and the corresponding collection in the code behind different names. This isn't going to cause a runtime issue, but it makes it hard to maintain the code ;)
Hope this helps :)

WPF Binding Via StaticResouces

Given the following Xaml:
<Window.Resources>
<System:String x:Key="StringValue"></System:String>
</Window.Resources>
<Grid>
<ComboBox Margin="137,101,169,183" ItemsSource="{Binding collection}" SnapsToDevicePixels="True" IsHitTestVisible="true">
<ComboBox.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<CheckBox Command="{Binding CheckCommand}" IsChecked="{Binding IsChecked}" Content="{Binding Name}"/>
<TextBlock Text="{StaticResource StringValue}" />
</StackPanel>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
</Grid>
What I want is for the Textblock Text to be bound to a static resource, that is databound to a value on the ViewModel. The issue is System.String appears to not allow databinding. ANybody know of a way to do this? For context, the TextBlock needs a different itemssource than that of its parent combobox.
Thanks.

String doesnt allow binding because it is not a DependencyObject (and doesnt implement INotifyPropertyChanged)
but why dont you just bind directly to the Value in the ViewModel?
if you cannot bind to a ViewModel (think about RelativeSource with searching Parent type) you can implement a wrapper (which implements INotifyPropertyChanged to get the changes in the object)
Example wrapper class:
public class BindWrapper<T> : INotifyPropertyChanged
{
private T _Content;
public T Content
{
get
{
return _Content;
}
set
{
_Content = value;
if (this.PropertyChanged != null)
this.PropertyChanged(this, new PropertyChangedEventArgs("Content"));
}
}
#region INotifyPropertyChanged Members
public event PropertyChangedEventHandler PropertyChanged;
#endregion
}
how to instantiate and bind in XAML:
<Window.Resources>
<local:BindWrapper x:Key="wrapper" x:TypeArguments="System:String">
<local:BindWrapper.Content>
<System:String>huuu</System:String>
</local:BindWrapper.Content>
</local:BindWrapper>
</Window.Resources>
<TextBlock Text="{Binding Source={StaticResource wrapper}, Path=Content}" />

To clarify, A System.String has no dependency properties so you can't bind it anything. I think you need a convertor so your TextBlock can bind to the View Model. What type of ObservableCollection do you have on the View Model?
EDIT If you just want to bind a simple string to the text property this is the wrong answer. If you want to bind to formatted text, read on.
I was having this problem before. I wanted to bind my TextBlock to a string resource in my properties. I ended up subclassing TextBlock to BindableTextBlock and making and a Convertor for string to an Inline list.
Question and Answers here.
It may seem a little involved, there ought to be an easier way. However I've resused the control several times whenever I've needed to bind to some formatted text and it works. Hopefully you can benefit from my work, and perhaps improve.