change ContentControl Content based on datacaontext

Question

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.

Answer 1

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: