How to manage User Control in List Box using MVVM?

How to manage User Control in List Box using MVVM? - c#

i know that there are many question of this, but i don't find the correct answer, or i don't understand the correct way to solve.
I have my list box in the MainWindows, it is populated by custom object (FooObjClass).
<ListBox x:Name="FooListBox">
<ListBox.ItemTemplate>
<DataTemplate>
<fooNameSpace:FooObjView/>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
the FooObjView is a User Control
<UserControl x:Class="PLCS7_TEST.SmartObjRecognize.SmartObjView"
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:Test.FooObjRecognize"
mc:Ignorable="d" Width="Auto">
<UserControl.DataContext>
<local:FooViewModel/>
</UserControl.DataContext>
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<TextBlock Grid.Column="0" Text="{Binding Path=FooObjprop.Name}"/>
<TextBlock Grid.Column="1" Text="{Binding Path=FooObjprop.Type}">
</Grid>
and this is my FooViewModel
class FooViewModel : ObservableObject
{
private FooObjClass fooObjmember;
public FooObjClass FooObjprop
{
get { return fooObjmember; }
set
{
this.fooObjmember= value;
base.RaisePropertyChanged("FooObjprop");
}
}
}
the FooObjClass is a normal class and the ObservableObject class is this:
public abstract class ObservableObject : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(PropertyChangedEventArgs e)
{
var handler = this.PropertyChanged;
if (handler != null)
{
handler(this, e);
}
}
protected void RaisePropertyChanged<T>(Expression<Func<T>> propertyExpresssion)
{
var propertyName = PropertySupport.ExtractPropertyName(propertyExpresssion);
this.RaisePropertyChanged(propertyName);
}
protected void RaisePropertyChanged(String propertyName)
{
VerifyPropertyName(propertyName);
OnPropertyChanged(new PropertyChangedEventArgs(propertyName));
}
public void VerifyPropertyName(String propertyName)
{
// verify that the property name matches a real,
// public, instance property on this Object.
if (TypeDescriptor.GetProperties(this)[propertyName] == null)
{
Debug.Fail("Invalid property name: " + propertyName);
}
}
}
Now, what i can do for pass the item object of the list box (it's a FooObjClass ) to the last FooModelView? I have to use the Dependency Property? But How? I tryed and i readed all, but i don't find solution
With this piece of code i would to pass the item object of the list box to the FooViewModel
<UserControl.DataContext>
<local:FooViewModel fooObjmember="{Databinding}"/>
</UserControl.DataContext>
but the fooObjmember is not a dependency property, and when i tried to create a dependency property it's the same
Thank you and sorry for my english ;)

Welcome,
Here are your errors:
You're not specifying the binding for a ListBoxItem
You are instantiating another model in the UserControl
You are binding to field fooObjmember, only properties are allowed
Here's a working example:
Window XAML
<Window x:Class="WpfApplication1.MainWindow"
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:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:WpfApplication1"
mc:Ignorable="d"
Title="MainWindow" Height="350" Width="525">
<Grid>
<!--<ListBox ItemsSource="{Binding}"> binds to DataContext property-->
<ListBox ItemsSource="{Binding}">
<ListBox.ItemTemplate>
<DataTemplate>
<local:MyUserControl DataContext="{Binding}" />
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</Grid>
</Window>
Window code
using System.Collections.Generic;
namespace WpfApplication1
{
public partial class MainWindow
{
public MainWindow()
{
InitializeComponent();
DataContext = new List<MyModel>
{
new MyModel {Number = 1, Value = "one"},
new MyModel {Number = 2, Value = "two"}
};
}
}
}
User control XAML
<UserControl x:Class="WpfApplication1.MyUserControl"
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:WpfApplication1"
mc:Ignorable="d" d:DataContext="{d:DesignInstance local:MyModel}"
d:DesignHeight="300" d:DesignWidth="300">
<Grid>
<Border Padding="5" BorderBrush="Red" BorderThickness="1">
<StackPanel>
<TextBlock Text="{Binding Number}" />
<TextBlock Text="{Binding Value}" />
</StackPanel>
</Border>
</Grid>
</UserControl>
User control code
namespace WpfApplication1
{
public partial class MyUserControl
{
public MyUserControl()
{
InitializeComponent();
}
}
}
Model code
using System.ComponentModel;
using System.Runtime.CompilerServices;
namespace WpfApplication1
{
internal class MyModel : INotifyPropertyChanged
{
private int _number;
private string _value;
public int Number
{
get { return _number; }
set
{
if (value == _number) return;
_number = value;
OnPropertyChanged();
}
}
public string Value
{
get { return _value; }
set
{
if (value == _value) return;
_value = value;
OnPropertyChanged();
}
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
}
Result
Now adjust that to your needs :D

Related

How can I pass DataContext to the UserControl using Command in WPF MVVM? [duplicate]

This question already has answers here:
How to pass data from MainWindow to a User Control that's inside the MainWindow?
(1 answer)
Issue with DependencyProperty binding
(3 answers)
Closed 1 year ago.
I am on practice using WPF MVVM with a YouTube video. I made menu buttons in a main window and UserControls, and when I click a menu the UserControl is shown in the main window. The MainViewModel has each ViewModel of the UserControl, and the shown UserControl is changed by changing CurrentView in the MainViewModel.
I want to set the DataContext in the UserControl before it is initialized, but I do not know how. I tried to change ViewModel member values in the MainViewModel, but the actual DataContext member variables in the UserControl are just null.
What I want to ask is how I can set the DataContext in the UserControl when it initialize. Or is there any way to access DataContext from MainWindow?
My Code is below:
Application.xaml
<Application x:Class="Practice.App"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:Practice"
xmlns:viewModel="clr-namespace:Practice.MVVM.ViewModel"
xmlns:view="clr-namespace:Practice.MVVM.View"
Startup="Application_Startup">
<Application.Resources>
<ResourceDictionary>
<DataTemplate DataType="{x:Type viewModel:HomeViewModel}">
<view:HomeView/>
</DataTemplate>
<DataTemplate DataType="{x:Type viewModel:UserViewModel}">
<view:UserView/>
</DataTemplate>
</ResourceDictionary>
</Application.Resources>
</Application>
MainWindow.xaml
<Window x:Class="Practice.MainWindow"
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:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:Practice"
xmlns:viewModel="clr-namespace:Practice.MVVM.ViewModel"
xmlns:view="clr-namespace:Practice.MVVM.View"
mc:Ignorable="d"
Title="Practice" MinHeight="800" MinWidth="1200"
WindowStyle="None"
ResizeMode="NoResize"
Background="Transparent"
AllowsTransparency="True"
Loaded="Window_Loaded">
<Window.DataContext>
<viewModel:MainViewModel/>
</Window.DataContext>
<Border Background="#002241"
CornerRadius="10">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="200"/>
<ColumnDefinition Width="1*"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="100"/>
<RowDefinition Height="1*"/>
</Grid.RowDefinitions>
<TextBlock Grid.Row="0" Grid.Column="0"
Text="Logo"
HorizontalAlignment="Center"
VerticalAlignment="Center"
FontSize="20"
Foreground="White"/>
<Grid Grid.Row="1" Grid.Column="0">
<Grid.RowDefinitions>
<RowDefinition Height="1*"/>
<RowDefinition Height="75"/>
</Grid.RowDefinitions>
<StackPanel Grid.Row="0">
<RadioButton Content="Home"
Height="50"
Foreground="White"
FontSize="16"
IsChecked="True"
Command="{Binding HomeViewCommand}"/>
<RadioButton Content="Users"
Height="50"
Foreground="White"
FontSize="16"
Command="{Binding UserViewCommand}"/>
</StackPanel>
</Grid>
<ContentControl Grid.Row="1" Grid.Column="1"
x:Name="CC_View"
Margin="10"
Content="{Binding CurrentView}"/>
</Grid>
</Border>
</Window>
HomeView.xaml
<UserControl x:Class="Practice.MVVM.View.HomeView"
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:Practice.MVVM.View"
xmlns:viewModel="clr-namespace:Practice.MVVM.ViewModel"
mc:Ignorable="d"
d:DesignHeight="450" d:DesignWidth="800">
<UserControl.DataContext>
<viewModel:HomeViewModel/>
</UserControl.DataContext>
<Grid>
</Grid>
</UserControl>
ObservableObject.cs
using System.ComponentModel;
using System.Runtime.CompilerServices;
namespace Practice.Core
{
public class ObservableObject : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged([CallerMemberName] string name = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
}
}
}
RelayCommand.cs
using System;
using System.Windows.Input;
namespace Practice.Core
{
public class RelayCommand:ICommand
{
private Action<object> _execute;
private Func<object, bool> _canExecute;
public event EventHandler CanExecuteChanged
{
add { CommandManager.RequerySuggested += value; }
remove { CommandManager.RequerySuggested -= value; }
}
public RelayCommand(Action<object> execute, Func<object, bool> canExecute = null)
{
_execute = execute;
_canExecute = canExecute;
}
public bool CanExecute(object parameter)
{
return _canExecute == null || _canExecute(parameter);
}
public void Execute(object parameter)
{
_execute(parameter);
}
}
}
MainViewModel.cs
namespace Practice.MVVM.ViewModel
{
public class MainViewModel : ObservableObject
{
public RelayCommand HomeViewCommand { get; set; }
public RelayCommand UserViewCommand { get; set; }
public HomeViewModel HomeVM { get; set; }
public UserViewModel UserVM { get; set; }
private object _currentView;
private object parameter1;
private object parameter2;
private object parameter3;
public object CurrentView
{
get { return _currentView; }
set
{
_currentView = value;
OnPropertyChanged();
}
}
public MainViewModel()
{
parameter1 = new object();
parameter2 = new object();
parameter3 = new object();
HomeVM = new HomeViewModel();
HomeVM.Initialize(parameter1, parameter2, parameter3);
UserVM = new UserViewModel();
CurrentView = HomeVM;
HomeViewCommand = new RelayCommand(o =>
{
CurrentView = HomeVM;
});
UserViewCommand = new RelayCommand(o =>
{
CurrentView = UserVM;
});
}
}
}
HomeViewModel.cs
namespace Practice.MVVM.ViewModel
{
public class HomeViewModel : ObservableObject
{
private object _parameter1;
private object _parameter2;
private object _parameter3;
public HomeViewModel()
{
}
public void Initialize(object parameter1, object parameter2, object parameter3)
{
_parameter1= parameter1;
_parameter2= parameter2;
_parameter3= parameter3;
}
}
}
Thank you in advance.

Custom Tooltip on LineChart (lvChart)

I closely follow step-by-step lvChart Customizing Tooltips in trying to build a custom tooltip for LineChart points. But I get empty tooltip content. Other than using ObservableValue for ChartValues type, my code is near identical to that used in the lvChart tutorial. I am not using any MV**.
Has anyone worked out the tutorial or apply custom tooltip on a LineChart?
Main.xaml
<lvc:CartesianChart.DataTooltip>
<local:MyTooltip />
</lvc:CartesianChart.DataTooltip>
Main.xaml.cs
MyTooltipContents = new ChartValues<MyTooltipContent>();
for (int i = 0; i < MyData.Count(); i++)
{
MyTooltipContents.Add(new MyTooltipContent
{
Name = "No" + i,
Value = "Foo"
});
}
var MyTooltipContentMapper = Mappers.Xy<MyTooltipContent>()
.X((value, index) => index)
.Y(value => 1);
//lets save the mapper globally
Charting.For<MyTooltipContent>(MyTooltipContentMapper);
DataContext = this;
MyTooltip.xaml
<UserControl x:Class="MyNamespace.MyTooltip"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:sys="clr-namespace:System;assembly=mscorlib"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:MyNamespace"
xmlns:lvc="clr-namespace:LiveCharts.Wpf;assembly=LiveCharts.Wpf"
mc:Ignorable="d"
d:DesignHeight="300" d:DesignWidth="300"
d:DataContext="{d:DesignInstance local:MyTooltip}"
Background="#E4555555" Padding="20 10" BorderThickness="2" BorderBrush="#555555">
<ItemsControl ItemsSource="{Binding Data.Points}" Grid.IsSharedSizeScope="True">
<ItemsControl.ItemTemplate>
<DataTemplate DataType="{x:Type lvc:DataPointViewModel}">
<Grid Margin="2">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="Auto" SharedSizeGroup="Name"/>
<ColumnDefinition Width="Auto" SharedSizeGroup="Value"/>
</Grid.ColumnDefinitions>
<TextBlock Grid.Column="1" Text="{Binding ChartPoint.Instance.(local:MyTooltipContent.Name)}"
Margin="5 0 0 0" VerticalAlignment="Center" Foreground="White" />
<TextBlock Grid.Column="2" Text="{Binding ChartPoint.Instance.(local:MyTooltipContent.Value)}"
Margin="5 0 0 0" VerticalAlignment="Center" Foreground="White"/>
</Grid>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</UserControl>
MyToolTip.xaml.cs
public partial class MyTooltip : IChartTooltip
{
private TooltipData _data;
public MyTooltip()
{
InitializeComponent();
DataContext = this;
}
public event PropertyChangedEventHandler PropertyChanged;
public TooltipData Data
{
get { return _data; }
set
{
_data = value;
OnPropertyChanged("Data");
}
}
public TooltipSelectionMode? SelectionMode { get; set; }
protected virtual void OnPropertyChanged(string propertyName = null)
{
if (PropertyChanged != null)
PropertyChanged.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
MyTooltipContent.cs
public class MyTooltipContent
{
public string Name { get; set; }
public string Value { get; set; }
}

I copied your example, and it works for me.
You might want to look at your MyTooltipContents declaration on your Main.xaml.cs, which should be a public property:
public ChartValues<MyTooltipContent> MyTooltipContents { get; set; }
I don't know exactly what gave you your line series, but I used this one on my MainWindow.xaml (corresponds to your Main.xaml):
<Window x:Class="MyToolTipExample.MainWindow"
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:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:MyToolTipExample"
xmlns:lvc="clr-namespace:LiveCharts.Wpf;assembly=LiveCharts.Wpf"
mc:Ignorable="d"
Title="MainWindow" Height="450" Width="800">
<Grid>
<lvc:CartesianChart LegendLocation="Right">
<lvc:CartesianChart.Series>
<lvc:LineSeries Title="Customers" Values="{Binding MyTooltipContents}"></lvc:LineSeries>
</lvc:CartesianChart.Series>
<lvc:CartesianChart.DataTooltip>
<local:MyTooltip/>
</lvc:CartesianChart.DataTooltip>
</lvc:CartesianChart>
</Grid>
</Window>
Note that MyTooltipContents is bound to the LineSeries.
EDIT: included screenshot.
Below, the full code example (.Net Framework 4.8 and LiveCharts 0.9.7):
1 - MainWindow.xaml.cs (the corresponding MainWindow.xaml is above):
namespace MyToolTipExample
{
public partial class MainWindow : Window
{
public ChartValues<MyTooltipContent> MyTooltipContents { get; set; }
public MainWindow()
{
InitializeComponent();
MyTooltipContents = new ChartValues<MyTooltipContent>();
for (int i = 0; i < 50; i++)
{
MyTooltipContents.Add(new MyTooltipContent
{
Name = $"No{i}",
Value = "Foo"
});
}
var MyTooltipContentMapper = Mappers.Xy<MyTooltipContent>()
.X((value, index) => index)
.Y(value => 1);
//lets save the mapper globally
Charting.For<MyTooltipContent>(MyTooltipContentMapper);
DataContext = this;
}
}
}
2 - the UserControl MyTooltip.xaml:
<UserControl x:Class="MyToolTipExample.MyTooltip"
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:lvc="clr-namespace:LiveCharts.Wpf;assembly=LiveCharts.Wpf"
xmlns:local="clr-namespace:MyToolTipExample"
mc:Ignorable="d"
d:DesignHeight="450" d:DesignWidth="800"
d:DataContext="{d:DesignInstance local:MyTooltip}"
Background="#45555555" Padding="20 10" BorderThickness="2" BorderBrush="#555555">
<ItemsControl ItemsSource="{Binding Data.Points}" Grid.IsSharedSizeScope="True">
<ItemsControl.ItemTemplate>
<DataTemplate DataType="{x:Type lvc:DataPointViewModel}">
<Grid Margin="2">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="Auto" SharedSizeGroup="Name"/>
<ColumnDefinition Width="Auto" SharedSizeGroup="Value"/>
</Grid.ColumnDefinitions>
<TextBlock Grid.Column="1" Text="{Binding ChartPoint.Instance.(local:MyTooltipContent.Name)}"
Margin="5 0 0 0" VerticalAlignment="Center" Foreground="White" />
<TextBlock Grid.Column="2" Text="{Binding ChartPoint.Instance.(local:MyTooltipContent.Value)}"
Margin="5 0 0 0" VerticalAlignment="Center" Foreground="White"/>
</Grid>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</UserControl>
3 - Code-behind the UserControl MyTooltip.xaml.cs:
using LiveCharts;
using LiveCharts.Wpf;
using System.ComponentModel;
using System.Windows.Controls;
namespace MyToolTipExample
{
public partial class MyTooltip : UserControl, IChartTooltip
{
public MyTooltip()
{
InitializeComponent();
DataContext = this;
}
private TooltipData _data;
public event PropertyChangedEventHandler PropertyChanged;
public TooltipData Data
{
get { return _data; }
set
{
_data = value;
OnPropertyChanged("Data");
}
}
public TooltipSelectionMode? SelectionMode { get; set; }
protected virtual void OnPropertyChanged(string propertyName = null)
{
if (PropertyChanged != null)
PropertyChanged.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
}
4 - Data model MyTooltipContent.cs (used by public property ChartValues):
namespace MyToolTipExample
{
public class MyTooltipContent
{
public string Name { get; set; }
public string Value { get; set; }
}
}
5 - Package.config:
<?xml version="1.0" encoding="utf-8"?>
<packages>
<package id="LiveCharts" version="0.9.7" targetFramework="net48" />
<package id="LiveCharts.Wpf" version="0.9.7" targetFramework="net48" />
</packages>
6 - The final solution structure should look something like this:

The application would be crashed when I used the PieChart to customize the ToolTip?
<Window x:Class="MyToolTipExample.MainWindow"
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:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:MyToolTipExample"
xmlns:lvc="clr-namespace:LiveCharts.Wpf;assembly=LiveCharts.Wpf"
mc:Ignorable="d"
Title="MainWindow" Height="450" Width="800">
<Grid>`enter code here`
<lvc:PieChart>
<lvc:PieChart.Series>
<lvc:PieSeries Fill="Green" Stroke="{x:Null}" StrokeThickness="0" />
</lvc:PieChart.Series>
<lvc:PieChart.DataTooltip>
<local:MyTooltip/>
</lvc:PieChart.DataTooltip>
</lvc:PieChart>
</Grid>
</Window>

Bind to property only if it exists

I have a WPF window that uses multiple viewmodel objects as its DataContext. The window has a control that binds to a property that exists only in some of the viewmodel objects. How can I bind to the property if it exists (and only if it exists).
I am aware of the following question/answer: MVVM - hiding a control when bound property is not present. This works, but gives me a warning. Can it be done without the warning?
Thanks!
Some example code:
Xaml:
<Window x:Class="WpfApplication1.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:WpfApplication1"
Title="MainWindow" Height="350" Width="525">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="40"/>
<RowDefinition Height="Auto"/>
<RowDefinition Height="40"/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<ListBox Grid.Row="1" Name="ListView" Margin="25,0,25,0" ItemsSource="{Binding Path=Lst}"
HorizontalContentAlignment="Center" SelectionChanged="Lst_SelectionChanged">
</ListBox>
<local:SubControl Grid.Row="3" x:Name="subControl" DataContext="{Binding Path=SelectedVM}"/>
</Grid>
SubControl Xaml:
<UserControl x:Class="WpfApplication1.SubControl"
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:WpfApplication1"
mc:Ignorable="d"
d:DesignHeight="200" d:DesignWidth="300">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="40"/>
<RowDefinition Height="Auto"/>
<RowDefinition Height="40"/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<StackPanel Grid.Row="1" Orientation ="Horizontal" HorizontalAlignment="Center" VerticalAlignment="Center" Margin="0,5,0,5">
<TextBlock Margin="5,0,5,0" Text="{Binding Path=OnOffAlways}"/>
<CheckBox IsChecked="{Binding Path=Always}">
<TextBlock Text="On/Off"/>
</CheckBox>
</StackPanel>
<StackPanel Grid.Row="3" Orientation ="Horizontal" HorizontalAlignment="Center" VerticalAlignment="Center" Margin="0,5,0,5">
<TextBlock Margin="5,0,5,0" Text="{Binding Path=OnOffSometimes}"/>
<CheckBox IsChecked="{Binding Path=Sometimes}">
<TextBlock Text="On/Off"/>
</CheckBox>
</StackPanel>
</Grid>
MainWindow Code Behind:
public partial class MainWindow : Window
{
ViewModel1 vm1;
ViewModel2 vm2;
MainViewModel mvm;
public MainWindow()
{
InitializeComponent();
vm1 = new ViewModel1();
vm2 = new ViewModel2();
mvm = new MainViewModel();
mvm.SelectedVM = vm1;
DataContext = mvm;
}
private void Lst_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
ListBox lstBx = sender as ListBox;
if (lstBx != null)
{
if (lstBx.SelectedItem.Equals("VM 1"))
mvm.SelectedVM = vm1;
else if (lstBx.SelectedItem.Equals("VM 2"))
mvm.SelectedVM = vm2;
}
}
}
MainViewModel (DataContext of MainWindow):
public class MainViewModel : INotifyPropertyChanged
{
ObservableCollection<string> lst;
ViewModelBase selectedVM;
public event PropertyChangedEventHandler PropertyChanged;
public MainViewModel()
{
Lst = new ObservableCollection<string>();
Lst.Add("VM 1");
Lst.Add("VM 2");
}
public ObservableCollection<string> Lst
{
get { return lst; }
set
{
lst = value;
OnPropertyChanged("Lst");
}
}
public ViewModelBase SelectedVM
{
get { return selectedVM; }
set
{
if (selectedVM != value)
{
selectedVM = value;
OnPropertyChanged("SelectedVM");
}
}
}
protected void OnPropertyChanged(string name)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(name));
}
}
}
ViewModel1 (with sometimes property):
public class ViewModel1 : ViewModelBase, INotifyPropertyChanged
{
private bool _always;
private string _onOffAlways;
private bool _sometimes;
private string _onOffSometimes;
public event PropertyChangedEventHandler PropertyChanged;
public ViewModel1()
{
_always = false;
_onOffAlways = "Always Off";
_sometimes = false;
_onOffSometimes = "Sometimes Off";
}
public bool Always
{
get { return _always; }
set
{
_always = value;
if (_always)
OnOffAlways = "Always On";
else
OnOffAlways = "Always Off";
OnPropertyChanged("Always");
}
}
public string OnOffAlways
{
get { return _onOffAlways; }
set
{
_onOffAlways = value;
OnPropertyChanged("OnOffAlways");
}
}
public bool Sometimes
{
get { return _sometimes; }
set
{
_sometimes = value;
if (_sometimes)
OnOffSometimes = "Sometimes On";
else
OnOffSometimes = "Sometimes Off";
OnPropertyChanged("Sometimes");
}
}
public string OnOffSometimes
{
get { return _onOffSometimes; }
set
{
_onOffSometimes = value;
OnPropertyChanged("OnOffSometimes");
}
}
protected void OnPropertyChanged(string name)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(name));
}
}
}
ViewModel2 (without Sometimes property):
public class ViewModel2 : ViewModelBase, INotifyPropertyChanged
{
private bool _always;
private string _onOffAlways;
public event PropertyChangedEventHandler PropertyChanged;
public ViewModel2()
{
_always = false;
_onOffAlways = "Always Off";
}
public bool Always
{
get { return _always; }
set
{
_always = value;
if (_always)
OnOffAlways = "Always On";
else
OnOffAlways = "Always Off";
OnPropertyChanged("Always");
}
}
public string OnOffAlways
{
get { return _onOffAlways; }
set
{
_onOffAlways = value;
OnPropertyChanged("OnOffAlways");
}
}
protected void OnPropertyChanged(string name)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(name));
}
}
}
public class AlwaysVisibleConverter : IValueConverter
{
#region Implementation of IValueConverter
public object Convert(object value,
Type targetType, object parameter, CultureInfo culture)
{
return Visibility.Visible;
}
public object ConvertBack(object value, Type targetType,
object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
#endregion
}

There are many different ways one could approach your scenario. For what it's worth, the solution you already have seems reasonable to me. The warning you get (I presume you are talking about the error message output to the debug console) is reasonably harmless. It does imply a potential performance issue, as it indicates WPF is recovering from an unexpected condition. But I would expect the cost to be incurred only when the view model changes, which should not be frequent enough to matter.
Another option, which is IMHO the preferred one, is to just use the usual WPF data templating features. That is, define a different template for each view model you expect, and then let WPF pick the right one according to the current view model. That would look something like this:
<UserControl x:Class="TestSO46736914MissingProperty.UserControl1"
x:ClassModifier="internal"
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:l="clr-namespace:TestSO46736914MissingProperty"
mc:Ignorable="d"
Content="{Binding}"
d:DesignHeight="300" d:DesignWidth="300">
<UserControl.Resources>
<DataTemplate DataType="{x:Type l:ViewModel1}">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="40"/>
<RowDefinition Height="Auto"/>
<RowDefinition Height="40"/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<StackPanel Grid.Row="1" Orientation ="Horizontal" HorizontalAlignment="Center" VerticalAlignment="Center" Margin="0,5,0,5">
<TextBlock Margin="5,0,5,0" Text="{Binding Path=OnOffAlways}"/>
<CheckBox IsChecked="{Binding Path=Always}">
<TextBlock Text="On/Off"/>
</CheckBox>
</StackPanel>
<StackPanel Grid.Row="3" Orientation ="Horizontal" HorizontalAlignment="Center" VerticalAlignment="Center" Margin="0,5,0,5">
<TextBlock Margin="5,0,5,0" Text="{Binding Path=OnOffSometimes}"/>
<CheckBox IsChecked="{Binding Path=Sometimes}">
<TextBlock Text="On/Off"/>
</CheckBox>
</StackPanel>
</Grid>
</DataTemplate>
<DataTemplate DataType="{x:Type l:ViewModel2}">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="40"/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<StackPanel Grid.Row="1" Orientation ="Horizontal" HorizontalAlignment="Center" VerticalAlignment="Center" Margin="0,5,0,5">
<TextBlock Margin="5,0,5,0" Text="{Binding Path=OnOffAlways}"/>
<CheckBox IsChecked="{Binding Path=Always}">
<TextBlock Text="On/Off"/>
</CheckBox>
</StackPanel>
</Grid>
</DataTemplate>
</UserControl.Resources>
</UserControl>
I.e. just set the Content of your UserControl object to the view model object itself, so that the appropriate template is used to display the data in the control. The template for the view model object that doesn't have the property, doesn't reference that property and so no warning is generated.
Yet another option, which like the above also addresses your concern about the displayed warning, is to create a "shim" (a.k.a. "adapter") object that mediates between the unknown view model type and a consistent one the UserControl can use. For example:
class ViewModelWrapper : NotifyPropertyChangedBase
{
private readonly dynamic _viewModel;
public ViewModelWrapper(object viewModel)
{
_viewModel = viewModel;
HasSometimes = viewModel.GetType().GetProperty("Sometimes") != null;
_viewModel.PropertyChanged += (PropertyChangedEventHandler)_OnPropertyChanged;
}
private void _OnPropertyChanged(object sender, PropertyChangedEventArgs e)
{
_RaisePropertyChanged(e.PropertyName);
}
public bool Always
{
get { return _viewModel.Always; }
set { _viewModel.Always = value; }
}
public string OnOffAlways
{
get { return _viewModel.OnOffAlways; }
set { _viewModel.OnOffAlways = value; }
}
public bool Sometimes
{
get { return HasSometimes ? _viewModel.Sometimes : false; }
set { if (HasSometimes) _viewModel.Sometimes = value; }
}
public string OnOffSometimes
{
get { return HasSometimes ? _viewModel.OnOffSometimes : null; }
set { if (HasSometimes) _viewModel.OnOffSometimes = value; }
}
private bool _hasSometimes;
public bool HasSometimes
{
get { return _hasSometimes; }
private set { _UpdateField(ref _hasSometimes, value); }
}
}
This object uses the dynamic feature in C# to access the known property values, and uses reflection on construction to determine whether or not it should try to access the Sometimes (and related OnOffSometimes) property (accessing the property via the dynamic-typed variable when it doesn't exist would throw an exception).
It also implements the HasSometimes property so that the view can dynamically adjust itself accordingly. Finally, it also proxies the underlying PropertyChanged event, to go along with the delegated properties themselves.
To use this, a little bit of code-behind for the UserControl is needed:
partial class UserControl1 : UserControl, INotifyPropertyChanged
{
public ViewModelWrapper ViewModelWrapper { get; private set; }
public UserControl1()
{
DataContextChanged += _OnDataContextChanged;
InitializeComponent();
}
public event PropertyChangedEventHandler PropertyChanged;
private void _OnDataContextChanged(object sender, DependencyPropertyChangedEventArgs e)
{
ViewModelWrapper = new ViewModelWrapper(DataContext);
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(ViewModelWrapper)));
}
}
With this, the XAML is mostly like what you originally had, but with a style applied to the optional StackPanel element that has a trigger to show or hide the element according to whether the property is present or not:
<UserControl x:Class="TestSO46736914MissingProperty.UserControl1"
x:ClassModifier="internal"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:p="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:l="clr-namespace:TestSO46736914MissingProperty"
mc:Ignorable="d"
d:DesignHeight="300" d:DesignWidth="300">
<Grid DataContext="{Binding ViewModelWrapper, RelativeSource={RelativeSource AncestorType=UserControl}}">
<Grid.RowDefinitions>
<RowDefinition Height="40"/>
<RowDefinition Height="Auto"/>
<RowDefinition Height="40"/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<StackPanel Grid.Row="1" Orientation ="Horizontal" HorizontalAlignment="Center" VerticalAlignment="Center" Margin="0,5,0,5">
<TextBlock Margin="5,0,5,0" Text="{Binding Path=OnOffAlways}"/>
<CheckBox IsChecked="{Binding Path=Always}">
<TextBlock Text="On/Off"/>
</CheckBox>
</StackPanel>
<StackPanel Grid.Row="3" Orientation ="Horizontal" HorizontalAlignment="Center" VerticalAlignment="Center" Margin="0,5,0,5">
<StackPanel.Style>
<p:Style TargetType="StackPanel">
<p:Style.Triggers>
<DataTrigger Binding="{Binding HasSometimes}" Value="False">
<Setter Property="Visibility" Value="Collapsed"/>
</DataTrigger>
</p:Style.Triggers>
</p:Style>
</StackPanel.Style>
<TextBlock Margin="5,0,5,0" Text="{Binding Path=OnOffSometimes}"/>
<CheckBox IsChecked="{Binding Path=Sometimes}">
<TextBlock Text="On/Off"/>
</CheckBox>
</StackPanel>
</Grid>
</UserControl>
Note that the top-level Grid element's DataContext is set to the UserControl's ViewModelWrapper property, so that the contained elements use that object instead of the view model assigned by the parent code.
(You can ignore the p: XML namespace…that's there only because Stack Overflow's XAML formatting gets confused by <Style/> elements that use the default XML namespace.)
While I in general would prefer the template-based approach, as the idiomatic and inherently simpler one, this wrapper-based approach does have some advantages:
It can be used in situations where the UserControl object is declared in an assembly different from the one where the view model types are declared, and where the latter assembly cannot be referenced by the former.
It removes the redundancy that is required by the template-based approach. I.e. rather than having to copy/paste the shared elements of the templates, this approach uses a single XAML structure for the entire view, and shows or hides elements of that view as appropriate.
For completeness, here is the NotifyPropertyChangedBase class used by the ViewModelWrapper class above:
class NotifyPropertyChangedBase : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected void _UpdateField<T>(ref T field, T newValue,
Action<T> onChangedCallback = null,
[CallerMemberName] string propertyName = null)
{
if (EqualityComparer<T>.Default.Equals(field, newValue))
{
return;
}
T oldValue = field;
field = newValue;
onChangedCallback?.Invoke(oldValue);
_RaisePropertyChanged(propertyName);
}
protected void _RaisePropertyChanged(string propertyName)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
For what it's worth, I prefer this approach to re-implementing the INotifyPropertyChanged interface in each model object. The code is a lot simpler and easier to write, simpler to read, and less prone to errors.

Here's a fairly simple solution using DataTriggers and a custom converter:
<Style TargetType="CheckBox">
<Style.Triggers>
<DataTrigger Binding="{Binding Converter={HasPropertyConverter PropertyName=Sometimes}}" Value="True">
<Setter Property="IsChecked" Value="{Binding Sometimes}" />
</DataTrigger>
</Style.Triggers>
</Style>
The converter:
public class HasPropertyConverter : IValueConverter
{
public string PropertyName { get; set; }
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
if (string.IsNullOrWhiteSpace(PropertyName))
return DependencyProperty.UnsetValue;
return value?.GetType().GetProperty(PropertyName) != null;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
=> throw new NotSupportedException();
}
public class HasPropertyConverterExtension : MarkupExtension
{
public string PropertyName { get; set; }
public override object ProvideValue(IServiceProvider serviceProvider)
=> new HasPropertyConverter { PropertyName = PropertyName };
}

probleme dealing with several view in mvvm

i'am currently building a software who as several view and i would like to switch from one view to another by clicking on a button on the current view :
of course i have more than 3 views but it's to illustrate the concept. here is my code to go from page 1 to page 2. but i have trouble to go from page 2 to page 3 i don't know what's wrong. thank you for your help.
MainWindow.xaml
<Controls:MetroWindow x:Class="maquette.MainWindow"
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:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:Controls="clr-namespace:MahApps.Metro.Controls;assembly=MahApps.Metro"
xmlns:local="clr-namespace:maquette"
xmlns:viewModel ="clr-namespace:maquette.ViewModel"
xmlns:view ="clr-namespace:maquette.View"
BorderBrush="{DynamicResource AccentColorBrush}"
BorderThickness="2"
mc:Ignorable="d"
Title="MainWindow">
<Window.Resources>
<DataTemplate DataType="{x:Type viewModel:page1ViewModel}">
<local:Page1/>
</DataTemplate>
<DataTemplate DataType="{x:Type viewModel:page2ViewModel}">
<view:Page2/>
</DataTemplate>
<DataTemplate DataType="{x:Type viewModel:page3ViewModel}">
<view:Page3/>
</DataTemplate>
<DataTemplate DataType="{x:Type viewModel:page4ViewModel}">
<view:Page4/>
</DataTemplate>
</Window.Resources>
<Grid>
<Controls:TransitioningContentControl x:Name="pagesControl"
Content="{Binding SelectedViewModel}"
Transition="Left"
/>
</Grid>
</Controls:MetroWindow>
MainWindow.cs
public MainWindow()
{
InitializeComponent();
var viewModel = new NavigationViewModel();
viewModel.SelectedViewModel = new page1ViewModel(viewModel);
this.DataContext = viewModel;
}
NavigationViewModel.cs
public class NavigationViewModel : INotifyPropertyChanged
{
private object selectedViewModel;
public object SelectedViewModel
{
get
{
return selectedViewModel;
}
set
{
selectedViewModel = value;
OnPropertyChanged("SelectedViewModel");
}
}
/// <summary>
///
/// </summary>
public event PropertyChangedEventHandler PropertyChanged;
private void OnPropertyChanged(string propName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propName));
}
}
}
Page1.xaml
<UserControl x:Class="maquette.Page1"
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:maquette.View"
xmlns:viewModel="clr-namespace:maquette.ViewModel"
d:DesignHeight="300" d:DesignWidth="300"
mc:Ignorable="d"
>
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="100"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<TextBlock x:Name="Title"
HorizontalAlignment="Center"
TextWrapping="Wrap"
VerticalAlignment="Center"
Width="320"
FontSize="30"
Grid.ColumnSpan="2"
FontFamily="Segoe UI"
FontWeight="Bold">File Control Program</TextBlock>
<Button x:Name="button"
HorizontalAlignment="Center"
VerticalAlignment="Center"
Grid.RowSpan="2"
Width="180"
Height="90"
Style="{StaticResource AccentedSquareButtonStyle}"
Command="{Binding Path=goSettings}"
>
<TextBlock Text="go page 2"
TextWrapping="Wrap"
TextAlignment="Center"/>
</Button>
</Grid>
</UserControl>
page1ViewModel
class page1ViewModel
{
public ICommand goSettings { get; set; }
private readonly NavigationViewModel _navigationViewModel;
public page1ViewModel(NavigationViewModel navigationViewModel)
{
_navigationViewModel = navigationViewModel;
goSettings = new BaseCommand(OpenSettings);
}
/// <summary>
///
/// </summary>
/// <param name="obj"></param>
private void OpenSettings(object obj)
{
_navigationViewModel.SelectedViewModel = new page2ViewModel();
}
}
page2.xaml
<UserControl x:Class="maquette.View.Page2"
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:Controls="clr-namespace:MahApps.Metro.Controls;assembly=MahApps.Metro"
xmlns:local="clr-namespace:maquette.View"
xmlns:view ="clr-namespace:maquette.View"
mc:Ignorable="d"
d:DesignHeight="300" d:DesignWidth="300"
Background="White">
<Grid>
<Button x:Name="button"
HorizontalAlignment="Center"
VerticalAlignment="Center"
Grid.ColumnSpan="2"
Grid.Row="4"
Width="180"
Height="80"
Style="{StaticResource AccentedSquareButtonStyle}"
Command="{Binding Path=goPage3}">
<TextBlock Text="Go page 3"
TextWrapping="Wrap"
TextAlignment="Center"
FontSize="20"
/>
</Button>
</Grid>
</UserControl>
page2.cs
public Page2()
{
InitializeComponent();
var viewModel = new NavigationViewModel();
DataContext = new page2ViewModel(viewModel);
}
page2ViewModel.cs
public class page2ViewModel
{
public ICommand goPage3 { get; set; }
private readonly NavigationViewModel _navigationViewModel;
public page2ViewModel()
{
}
public page2ViewModel(NavigationViewModel navigationViewModel)
{
_navigationViewModel = navigationViewModel;
goPage3 = new BaseCommand(OpenPage3);
}
/// <summary>
///
/// </summary>
/// <param name="obj"></param>
private void OpenPage3(object obj)
{
_navigationViewModel.SelectedViewModel = new page3ViewModel();
}
}
But as i said the transition between the page 2 and 3 doesn't work. any help ? thank you !

Remove this constructor overload from page2ViewModel:
public page2ViewModel()
{
}
And always inject it with the one and only NavigationViewModel in page1ViewModel:
private void OpenSettings(object obj)
{
_navigationViewModel.SelectedViewModel = new page2ViewModel(_navigationViewModel);
}
Also don't set the DataContext of Page2 explicitly:
public Page2()
{
InitializeComponent();
}
The data templating will make sure that it gets the correct DataContext.

This is for Without using any mvvm framework
Define Data Templates for child viewmodels in Main window viewmodel.
For entire application u have to create static object for your main view model.
Then only views will be changed.
It should be like this...
public partial class App : Application
{
public static MainWindowViewModel mainWindowViewModel;
public App()
{
mainWindowViewModel = new MainWindowViewModel();
}
}
In MainWindow Viewmodel
public class MainWindowViewmodel
{
private object selectedViewModel;
public object SelectedViewModel
{
get
{
return selectedViewModel;
}
set
{
selectedViewModel = value;
OnPropertyChanged("SelectedViewModel");
}
}
public MainWindowViewmodel()
{
SelectedViewModel = new page1viewmodel();
}
}
In Page1Viewmodel in
class page1ViewModel
{
public ICommand goSettings { get; set; }
private readonly NavigationViewModel _navigationViewModel;
public page1ViewModel(NavigationViewModel navigationViewModel)
{
_navigationViewModel = navigationViewModel;
goSettings = new BaseCommand(OpenSettings);
}
/// <summary>
///
/// </summary>
/// <param name="obj"></param>
private void OpenSettings(object obj)
{
mainWindowViewModel.SelectedViewModel = new page2ViewModel();
}
}
like this you have to implement.
This will help you.

Custom dependency property binding

I got some problem with custom dependency property binding.
We have:
Custom user control with one dependency property and binding to self:
<UserControl x:Class="WpfApplication1.SomeUserControl"
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"
mc:Ignorable="d"
d:DesignHeight="300" d:DesignWidth="300" DataContext="{Binding RelativeSource={RelativeSource Mode=Self}}">
<Grid>
<Label>
<Label.Template>
<ControlTemplate>
<Label Content="{Binding MyTest}"/>
</ControlTemplate>
</Label.Template>
</Label>
</Grid>
... and code of control:
public partial class SomeUserControl : UserControl
{
public SomeUserControl()
{
InitializeComponent();
}
public static readonly DependencyProperty MyTestProperty = DependencyProperty.Register("MyTest", typeof(int), typeof(SomeUserControl));
public int MyTest
{
get { return (int)GetValue(MyTestProperty); }
set { SetValue(MyTestProperty, value); }
}
}
I trying to use this control with binding to some simple property of simple model class:
<UserControl x:Class="WpfApplication1.AnotherUserControl"
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:wpfApplication1="clr-namespace:WpfApplication1"
mc:Ignorable="d"
d:DesignHeight="300" d:DesignWidth="300" DataContext="{Binding RelativeSource={RelativeSource Mode=Self}}">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<wpfApplication1:SomeUserControl MyTest="{Binding Path=Model.MyNum}" Grid.Column="0"/>
<Label Content="{Binding Path=Model.MyNum}" Grid.Column="1"/>
</Grid>
... with code
public partial class AnotherUserControl : UserControl
{
public MyModel Model { get; set; }
public AnotherUserControl()
{
Model = new MyModel();
Model.MyNum = 1231;
InitializeComponent();
}
}
... and model:
public class MyModel:INotifyPropertyChanged
{
private int _myNum;
public int MyNum
{
get { return _myNum; }
set { _myNum = value; OnPropertyChanged("MyNum");}
}
public event PropertyChangedEventHandler PropertyChanged;
[NotifyPropertyChangedInvocator]
protected virtual void OnPropertyChanged(string propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
}
}
But binding is not working. Stack have no errors in compilation. Now, binding working with statndart wpf label control (with same model), and don't working with my custom control and custom property. Please help me to understand reasons of this problem and solve it;
Thanks)

You should use ElementName Binding in your SomeUserControl.
<UserControl x:Class="WpfApplication1.SomeUserControl"
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"
mc:Ignorable="d"
d:DesignHeight="300" d:DesignWidth="300"
x:Name="uc">
<Grid>
<Label>
<Label.Template>
<ControlTemplate>
<Label Content="{Binding MyTest, ElementName=uc}"/>
</ControlTemplate>
</Label.Template>
</Label>
</Grid>
here some more information why you should not set the datacontext of a usercontrol to self/this.
Data Binding in WPF User Controls

You will need to update your binding as below i.e you will have to bind to the ancestor usercontrol property using RelativeSource as you are setting the DataContext of child usercontrol explicitly, default binding will search for path inside the child userControl's DataContext.
<wpfApplication1:SomeUserControl MyTest="{Binding Path=DataContext.Model.MyNum, RelativeSource={RelativeSource FindAncestor={x:Type UserControl}}}" Grid.Column="0"/>

We Keep Coding

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