How to switch contenttemplate dependent which view model object?-CodePudding

How to settings which view showup when specific viewmodel set? i read this explain with data template but i still dont understand. cause it dont show all code that use data template as switch view. https://learn.microsoft.com/en-us/archive/msdn-magazine/2009/february/patterns-wpf-apps-with-the-model-view-viewmodel-design-pattern

<Window x:Class="Pandora.Views.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:vm="clr-namespace:Pandora.ViewModels"
        Title="Pandora" Height="350" Width="525">
    <Window.ContentTemplate>
            <DataTemplate DataType="{x:Type vm:IndexViewModel}">
                <TextBlock>Index Content</TextBlock>
            </DataTemplate>

            <DataTemplate DataType="{x:Type vm:DashboardViewModel}">
                <TextBlock>Dashboard Content</TextBlock>
            </DataTemplate>
    </Window.ContentTemplate>
</Window>

using Pandora.ViewModels;

namespace Pandora.Views;

public partial class MainWindow
{
    public MainWindow()
    {
      InitializeComponent();
      DataContext = new IndexViewModel();
    }
}

CodePudding user response：

For Window to show anything it should have some Content (empty Window template contains <Grid></Grid> element). Simply copy Content from DataContext by using binding.

In your case you want to show elements, which don't have visual representation of their own (IndexViewModel, DashboardViewModel), so they require a custom DataTemplate. You already have, just put them in Resources.

<Window x:Class="Pandora.Views.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:vm="clr-namespace:Pandora.ViewModels"
        Title="Pandora" 
        Content="{Binding}"
        Height="350" Width="525">
    <Window.Resources>
        <DataTemplate DataType="{x:Type vm:IndexViewModel}">
            <TextBlock>Index Content</TextBlock>
        </DataTemplate>

        <DataTemplate DataType="{x:Type vm:DashboardViewModel}">
            <TextBlock>Dashboard Content</TextBlock>
        </DataTemplate>
    </Window.Resources>
</Window>

or more common method which uses a separate element to insert custom content:

<Window x:Class="Pandora.Views.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:vm="clr-namespace:Pandora.ViewModels"
        Title="Pandora" 
        Height="350" Width="525">
    <Window.Resources>
        <DataTemplate DataType="{x:Type vm:IndexViewModel}">
            <TextBlock>Index Content</TextBlock>
        </DataTemplate>

        <DataTemplate DataType="{x:Type vm:DashboardViewModel}">
            <TextBlock>Dashboard Content</TextBlock>
        </DataTemplate>
    </Window.Resources>
    <Grid>
         <ContentPresenter Content="{Binding}"/>
         <TextBlock Text="Demo watermark" VerticalAlignment="Center" HorizontalAlignment="Center" IsHitTestVisible="False"/>
    </Grid>
</Window>

CodePudding user response：

You must assign the IndexViewModel or DashboardViewModel instance to the Window.Content property. The ContentTemplate applies to the data object that is the current value of the Content property:

public partial class MainWindow
{
    public MainWindow()
    {
      InitializeComponent();
      this.Content = new IndexViewModel();
    }
}