I have a problem with binding an DependencyProperty of type ICommand. This is my custom user control:
<UserControl x:Class="HexEditor.Controls.NavButton"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:local="using:HexEditor.Controls"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
d:DesignHeight="300"
d:DesignWidth="400"
DataContext="{Binding RelativeSource={RelativeSource Self}}"
mc:Ignorable="d">
<ToggleButton x:Name="toggleWrap"
Width="140"
Height="48"
Background="Transparent"
BorderThickness="0"
Command="{Binding Command}"
CommandParameter="{Binding CommandParameter}"
IsChecked="{Binding IsChecked}">
<Grid Width="140">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto" />
<ColumnDefinition Width="*" />
</Grid.ColumnDefinitions>
<FontIcon Margin="6,0,0,0"
Glyph="{Binding Icon}" />
<TextBlock Grid.Column="1"
Margin="32,0,0,0"
Text="{Binding Title}" />
</Grid>
</ToggleButton>
</UserControl>
This is code behind of my control:
public sealed partial class NavButton : UserControl
{
public NavButton()
{
this.InitializeComponent();
}
public static readonly DependencyProperty IconProperty =
DependencyProperty.Register("Icon", typeof(string), typeof(FontIcon), new PropertyMetadata(""));
public static readonly DependencyProperty TitleProperty =
DependencyProperty.Register("Title", typeof(string), typeof(TextBlock), new PropertyMetadata(""));
public static readonly DependencyProperty IsCheckedProperty =
DependencyProperty.Register("IsChecked", typeof(bool), typeof(ToggleButton), new PropertyMetadata(""));
public static readonly DependencyProperty CommandProperty =
DependencyProperty.Register("Command", typeof(ICommand), typeof(ToggleButton), new PropertyMetadata(""));
public static readonly DependencyProperty CommandParameterProperty =
DependencyProperty.Register("CommandParameter", typeof(object), typeof(ToggleButton), new PropertyMetadata(""));
public string Icon
{
get { return (string)GetValue(IconProperty); }
set { SetValue(IconProperty, value); }
}
public string Title
{
get { return (string)GetValue(TitleProperty); }
set { SetValue(TitleProperty, value); }
}
public bool IsChecked
{
get { return Convert.ToBoolean(GetValue(IsCheckedProperty)); }
set { SetValue(IsCheckedProperty, value); }
}
public ICommand Command
{
get { return (ICommand)GetValue(CommandProperty); }
set { SetValue(CommandProperty, value); }
}
public object CommandParameter
{
get { return GetValue(CommandParameterProperty); }
set { SetValue(CommandParameterProperty, value); }
}
}
And this is a page where i use my control:
<UserControl x:Class="HexEditor.Common.RootFrame"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:Controls="using:HexEditor.Controls"
xmlns:Interactions="using:Microsoft.Xaml.Interactions.Core"
xmlns:Interactivity="using:Microsoft.Xaml.Interactivity"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:local="using:HexEditor.Common"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
d:DesignHeight="300"
d:DesignWidth="400"
DataContext="{Binding CommonViewModel,
Source={StaticResource Locator}}"
mc:Ignorable="d">
<Grid Background="White">
<SplitView x:Name="navSplitView"
Width="Auto"
DisplayMode="CompactOverlay"
OpenPaneLength="140">
<SplitView.Pane>
<StackPanel>
<ToggleButton x:Name="hamBtn"
Width="48"
Height="48"
BorderThickness="0">
<FontIcon Glyph="" />
</ToggleButton>
<Controls:NavButton Title="Home"
Command="{Binding NavigationCommand}"
CommandParameter="HomePage"
Icon=""
IsChecked="True" />
<Controls:NavButton Title="Settings"
Command="{Binding NavigationCommand}"
CommandParameter="SettingsPage"
Icon=""
IsChecked="False" />
</StackPanel>
</SplitView.Pane>
<SplitView.Content>
<Frame x:Name="NavFrame" />
</SplitView.Content>
<Interactivity:Interaction.Behaviors>
<Interactions:DataTriggerBehavior Binding="{Binding IsChecked,
ElementName=hamBtn}"
Value="True">
<Interactions:ChangePropertyAction PropertyName="IsPaneOpen"
TargetObject="{Binding ElementName=navSplitView}"
Value="True" />
</Interactions:DataTriggerBehavior>
<Interactions:DataTriggerBehavior Binding="{Binding IsChecked,
ElementName=hamBtn}"
Value="False">
<Interactions:ChangePropertyAction PropertyName="IsPaneOpen"
TargetObject="{Binding ElementName=navSplitView}"
Value="False" />
</Interactions:DataTriggerBehavior>
</Interactivity:Interaction.Behaviors>
</SplitView>
</Grid>
</UserControl>
Here's the ViewModel:
public class CommonViewModel : ViewModelBase
{
public CommonViewModel()
{
this.NavigationCommand = new RelayCommand<NavigationSource>(this.ExecuteNavigationCommand);
}
public ICommand NavigationCommand { get; private set; }
private void ExecuteNavigationCommand(NavigationSource state)
{
NavigationProvider.Instance.NavigateTo(state);
}
}
When compiling, exception appears:
Exception thrown: 'System.InvalidCastException' in HexEditor.exe
'HexEditor.exe' (CoreCLR: CoreCLR_UWP_Domain): Loaded 'C:\Users\Root\documents\visual studio 2015\Projects\HexEditor\HexEditor\bin\x86\Debug\AppX\System.Resources.ResourceManager.dll'. Module was built without symbols.
Exception thrown: 'Windows.UI.Xaml.Markup.XamlParseException' in HexEditor.exe
WinRT information: Failed to assign to property 'HexEditor.Controls.NavButton.Command'. [Line: 29 Position: 41]
An exception of type 'Windows.UI.Xaml.Markup.XamlParseException' occurred in HexEditor.exe but was not handled in user code
WinRT information: Failed to assign to property 'HexEditor.Controls.NavButton.Command'. [Line: 29 Position: 41]
Additional information: The text associated with this error code could not be found.
Failed to assign to property 'HexEditor.Controls.NavButton.Command'. [Line: 29 Position: 41]
What i'm doing wrong?
I think the problem is that you have default values of "" for dependency properties of type bool
and ICommand
(new PropertyMetadata("")
in both cases). You can't cast a string to either one, and that will cause an exception to be thrown. IsChecked
should default to false
, and Command
should default to null
.
This may or may not be relevant to the exact issue you're asking about, but it matters too: The third parameter of DependencyProperty.Register() should be the type of the owning class. That's typeof(NavButton)
in your case, for all of its dependency properties.