change ContentControl Content based on datacaontext

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question

essamce asked Mar 22, '21 essamce commented Mar 24, '21

change ContentControl Content based on datacaontext

hi
i'm trying to change ContentControl.Content at run time based on ContentControl.DataContext, so at run time i change ContentControl.DataContext Source property and i want the ContentControl.Content to be changed based on the ContentControl.DataContext Source property new value,
here is my try:

 <UserControl 
     x:Class="wpf1.UI.View.CurrentView"
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
     xmlns:vm="clr-wpf1.UI.ViewModel"
     xmlns:view="clr-namespace:wpf1.UI.View"
     DataContext="{Binding}">
     <UserControl.Resources>
         <DataTemplate DataType="{x:Type vm:MyViewModel1}">
             <view:MyViewModel1View DataContext="{Binding}"/>
         </DataTemplate>
         <DataTemplate DataType="{x:Type vm:MyViewModel2}">
             <view:MyViewModel2View DataContext="{Binding}"/>
         </DataTemplate>
     </UserControl.Resources>
     <ContentControl DataContext="{Binding}" />
 </UserControl>

and here is how i use it in mainwindow

 <view:CurrentView
             Grid.Row="2"
             DataContext="{Binding CurrentVM}"/>

and here is the mainwindow viewmodel

 ...
 private ViewModelBase _currentVM;
  public ViewModelBase CurrentVM
         {
             get => _currentVM;
             set
             {
                 _currentVM = value;
                 OnPropertyChanged(nameof(CurrentVM));
             }
         }
    
         MyViewModel1 _myVM1;
         MyViewModel2 _myVM2;
 ...
    
 // at some point i do so
 CurrentVM = _myVM1;
    
 // at some point i do so
 CurrentVM = _myVM2;

i want the CurrentView control to have only one view which matches it's datacontext.
i'm using .NetFramework 4.7 VS2019
any help will be appreciated, thanks in advance.

windows-wpf dotnet-wpf-xaml

· 1

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essamce · Mar 23, 2021 at 05:59 AM

anyone can help me , is there a way to do that without TemplateSelectror ?

0 ·

Answer 1 · 2021-03-23T07:49:07.287Z

PeterFleischer-3316 answered Mar 23, '21

Hi,
in ContentControl you can use Content = {Binding CurrentVM}.

Try following demo:

XAML MainWindow:

 <Window x:Class="WpfApp1.Window033"
         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:WpfApp033"
         xmlns:view="clr-namespace:WpfControlLibrary1;assembly=WpfControlLibrary1"
         mc:Ignorable="d"
         Title="MainWindow" Height="450" Width="800">
   <Window.DataContext>
     <local:ViewModel/>
   </Window.DataContext>
   <StackPanel>
     <Button Content="Switch" Command="{Binding}" Width="200" Margin="5"/>
     <view:Window033UC1 DataContext="{Binding CurrentVM}"/>
   </StackPanel>
 </Window>

Main ViewModel:

 using System;
 using System.ComponentModel;
 using System.Runtime.CompilerServices;
 using System.Windows;
 using System.Windows.Input;
    
 namespace WpfApp033
 {
   public class ViewModel : ICommand, INotifyPropertyChanged
   {
     public object CurrentVM { get; set; } = new WpfControlLibrary033.MyViewModel1();
    
     public void Execute(object parameter)
     {
       if (CurrentVM is WpfControlLibrary033.MyViewModel2)
         CurrentVM = new WpfControlLibrary033.MyViewModel1() { Info1 = DateTime.Now.ToString("mm:ss.fff") };
       else CurrentVM = new WpfControlLibrary033.MyViewModel2() { Info2 = DateTime.Now.ToString("mm:ss.fff") };
       OnPropertyChanged(nameof(CurrentVM));
     }
    
     public event EventHandler CanExecuteChanged;
     public bool CanExecute(object parameter) => true;
    
     public event PropertyChangedEventHandler PropertyChanged;
     private void OnPropertyChanged([CallerMemberName] string propName = "") => 
       PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propName));
   }
 }

XAML UserControl:

 <UserControl x:Class="WpfControlLibrary1.Window033UC1"
              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:WpfControlLibrary1"
              xmlns:view="clr-namespace:WpfControlLibrary033"
              xmlns:vm="clr-namespace:WpfControlLibrary033"
              mc:Ignorable="d" 
              d:DesignHeight="450" d:DesignWidth="800">
     <UserControl.Resources>
       <DataTemplate DataType="{x:Type vm:MyViewModel1}">
         <view:MyViewModel1View DataContext="{Binding}"/>
       </DataTemplate>
       <DataTemplate DataType="{x:Type vm:MyViewModel2}">
         <view:MyViewModel2View DataContext="{Binding}"/>
       </DataTemplate>
     </UserControl.Resources>
     <ContentControl Content="{Binding}"/>
 </UserControl>

ViewModels for UserControls:

 using System.Windows.Controls;
 using System.Windows.Data;
    
 namespace WpfControlLibrary033
 {
   public class MyViewModel1
   {
     public string Info1 { get; set; }
   }
   public class MyViewModel2
   {
     public string Info2 { get; set; }
   }
   public class MyViewModel1View : UserControl
   {
     public MyViewModel1View()
     {
       StackPanel stp = new StackPanel();
       this.Content = stp;
       stp.Children.Add(new Label() { Content = "1. View" });
       Label lbl = new Label();
       lbl.SetBinding(Label.ContentProperty, new Binding("Info1"));
       stp.Children.Add(lbl);
     }
   }
   public class MyViewModel2View : UserControl
   {
     public MyViewModel2View()
     {
       StackPanel stp = new StackPanel();
       this.Content = stp;
       stp.Children.Add(new Label() { Content = "2. View" });
       Label lbl = new Label();
       lbl.SetBinding(Label.ContentProperty, new Binding("Info2"));
       stp.Children.Add(lbl);
     }
   }
 }

Result:

x.gif (45.4 KiB)

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