WPF custom control: Proper way to react to property changes [duplicate] - wpf

Question

This question already has answers here:
DependencyProperty not triggered
(2 answers)
Callback when dependency property recieves xaml change
(2 answers)
Closed 1 year ago.
I have created a custom control in WPF: ChannelsDisplay, a kind of very simple charts control. For testing the control I use a MVVM test application:
View
<UserControl x:Class="UI.CustomControls.TestApp.Views.ChannelsDisplayView"
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:local="clr-namespace:UI.CustomControls.TestApp.Views"
xmlns:ucc="clr-namespace:UI.CustomControls;assembly=UI.CustomControls"
xmlns:viewmodels="clr-namespace:UI.CustomControls.TestApp.ViewModels"
d:DataContext="{d:DesignInstance Type=viewmodels:ChannelsDisplayViewModel}"
mc:Ignorable="d"
d:DesignHeight="450" d:DesignWidth="800">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="*"/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<ucc:ChannelsDisplay Lines="{Binding Lines}"
ChannelsYSpacing="{Binding YSpacing, Mode=TwoWay}"/>
<StackPanel Grid.Row="1" Orientation="Vertical">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<Label Content="ChannelsYSpacing" />
<Slider Grid.Column="1"
Value="{Binding YSpacing, Mode=TwoWay}"
Minimum="0" Maximum="99" IsSnapToTickEnabled="True"/>
<TextBox Grid.Column="2" Text="{Binding YSpacing}"/>
</Grid>
</StackPanel>
</Grid>
</UserControl>
ViewModel
public class ChannelsDisplayViewModel : ObservableObject, IPageViewModel
{
public string Name => "ChannelsDisplay";
public ObservableCollection<List<int>> Lines { get; set; }
public int YSpacing
{
get { return ySpacing; }
set
{
if (value != ySpacing)
{
loginViewModel = value;
OnPropertyChanged(nameof(YSpacing));
}
}
}
// ...
};
In the view there is a Slider, a TextBox and the ChannelsDisplay, all of them bind to the view model property YSpacing. The aim is that the Slider can change the YSpacing of my ChannelsDisplay.
So the ChannelsDisplay has among other things a property ChannelsYSpacing, which is implemented as a full DependencyProperty:
/// <summary>
/// Y-Distance between each band of data
/// </summary>
[Category("Common")]
public int ChannelsYSpacing
{
get => (int)GetValue(ChannelsYSpacingProperty);
set
{
SetValue(ChannelsYSpacingProperty, value);
createScaledLines();
createVisibleLines();
updateCanvas();
}
}
/// <summary>
/// Identifies the <see cref="Lines"/> dependency property.
/// </summary>
public static readonly DependencyProperty ChannelsYSpacingProperty =
DependencyProperty.Register("ChannelsYSpacing",
typeof(int),
typeof(ChannelsDisplay),
new FrameworkPropertyMetadata(20, new PropertyChangedCallback(OnSpacingChanged)));
The problem is, if the bound value of ChannelsYSpacing changes (E.g. the slider was moved by the user) the ChannelsDisplay custom control must be updated and redrawn. And the only way to do it that I could find out to write some code into the PropertyChangedCallback:
private static void OnSpacingChanged(DependencyObject d,
DependencyPropertyChangedEventArgs e)
{
ChannelsDisplay channelsDisplay = (ChannelsDisplay)d;
if(e.Property.Name == nameof(ChannelsYSpacing))
{
channelsDisplay.ChannelsYSpacing = (int)e.NewValue;
}
}
So the custom controls property ChannelsYSpacing will be set to e.NewValue and the property setter then calls createScaledLines(), createVisibleLines() and updateCanvas().
That works, the control is updated when the slider is moved. But going through the callback handler and writing things like if (e.Property.Name == nameof(ChannelsYSpacing)) somehow feels not right. It feelslike overhead. Ist this really necessary or is there a better way to do it?