Data Binding in WPF User Controls

c#, data-binding, user-controls, wpf, xaml

Solution

if you look at your output window you should see the binding exception.

The problem you have is the following: within your usercontrol you will bind the label to the DP ProtocolNumber of your usercontrol and not the `DataContext`, so you have to add for example the element name to the binding.

<UserControl Name="MainOptionsPanel"
    x:Class="ExperienceMainControls.MainControls"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    x:Name="uc"
    >
<Label Height="Auto" Name="numberLabel">Protocol:</Label>
<Label Content="{Binding Path=ProtocolNumber, ElementName=uc}" Name="protocolNumberLabel"/>
(...)
</UserControl>

EDIT: to clear some things up, your usercontrol also works if you change the binding in your MainWindow. but you have to bind to the DataContext of the MainWindow with RelativeSource.

    <expControl:MainControls ProtocolNumber="{Binding Path=Number, RelativeSource={RelativeSource AncestorType={x:Type Window}}}" />

Problem

I am creating a UserControl for a series of controls shared by several windows. One of the controls is a Label which shows the flow of some other process in terms of "protocol numbers". I am trying to offer DataBinding with this Label so the Window automatically reflects the state of the process as the protocol number variable changes. This is the User control XAML: ``` <UserControl Name="MainOptionsPanel" x:Class="ExperienceMainControls.MainControls" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" DataContext="{Binding RelativeSource={RelativeSource Self}}" > <Label Height="Auto" Name="numberLabel">Protocol:</Label> <Label Content="{Binding Path=ProtocolNumber}" Name="protocolNumberLabel"/> (...) </UserControl> ``` And this is the Code-Behind: ``` public partial class MainControls { public MainControls() { InitializeComponent(); } public int ProtocolNumber { get { return (int)GetValue(ProtocolNumberProperty); } set { SetValue(ProtocolNumberProperty, value); } } public static DependencyProperty ProtocolNumberProperty = DependencyProperty.Register("ProtocolNumber", typeof(int), typeof(MainControls)); } ``` This seems to be working because if on the constructor I set ProtocolNumber to an arbitrary value, it is reflected in the user control. However, when using this usercontrol on the final window, the data binding breaks. XAML: ``` <Window x:Class="UserControlTesting.Window1" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:expControl="clr-namespace:ExperienceMainControls;assembly=ExperienceMainControls" DataContext="{Binding RelativeSource={RelativeSource Self}}" > <StackPanel> <expControl:MainControls ProtocolNumber="{Binding Path=Number, Mode=TwoWay}" /> </StackPanel> </Window> ``` Code-Behind for window: ``` public partial class Window1 : Window { public Window1() { Number= 15; InitializeComponent(); } public int Number { get; set; } } ``` This sets the Protocol Number to zero, ignoring the value set to Number. I've read example

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