A library that will help with displaying fake data in the Designer in Visual Studio. You shouldn't have to run your app to see what it looks like while you are editing XAML.

The package is installed via nuget.org:

• Package Manager Console: Install-Package dotnetKyle.WpfDesignerHelper
• Dotnet CLI: dotnet add package dotnetKyle.WpfDesignerHelper

In your ViewModel's constructor, you can set the properties that are bound and this code will only run in the designer and won't affect runtime code.

using WpfDesignerHelper;

namespace Example
{
    public class AutoMobileViewModel
    {
        public MyViewModel()
        {
            if(Designer.Active)
            {
                this.Make = "Toyota";
                this.Model = "Tacoma";
                this.Year = "2020";
                this.WheelSizes = new string[]
                { 
                    "265/75 R15", "265/75 R15", 
                    "265/75 R15", "265/75 R15" 
                };
            }
        }

        public string Make { get; set; }
        public string Model { get; set; }
        public string Year { get; set; }
        public IEnumerable<string> WheelSizes { get; set; }    
    }
}

In the XAML for the View that uses the View Model, you can specify a > design-time ViewModel by setting the d:DataContext to use, like this:

<Window x:Class="Example.MainWindow"
        ...
        xmlns:local="clr-namespace:Example"
        mc:Ignorable="d"
        d:DataContext="{d:DesignInstance Type=local:AutoMobileViewModel, > IsDesignTimeCreatable=True}"
        ...
        >
        <!-- Most important part is the above d:DataContext line. -->
    <StackPanel Orientation="Vertical">
        <!-- Make -->
        <StackPanel Orientation="Horizontal">
            <Label Content="Make:"/>
            <TextBlock Text={Binding Make}/>
        </StackPanel>

        <!-- Model -->
        <StackPanel Orientation="Horizontal">
            <Label Content="Model:"/>
            <TextBlock Text={Binding Model}/>
        </StackPanel>

        <!-- Year -->
        <StackPanel Orientation="Horizontal">
            <Label Content="Year:"/>
            <TextBlock Text={Binding Year}/>
        </StackPanel>
        
        <!-- Wheels -->
        <StackPanel Orientation="Horizontal">
            <Label Content="Wheels:"/>
            <ItemsControl ItemsSource="{Binding WheelSizes}">
                <ItemsControl.ItemsPanel>
                    <ItemsPanelTemplate>
                        <StackPanel Orientation="Vertical"/>
                    </ItemsPanelTemplate>
                </ItemsControl.ItemsPanel>
                <ItemsControl.ItemTemplate>
                    <DataTemplate>
                        <TextBlock Text="{Binding}"/>
                    </DataTemplate>
                </ItemsControl.ItemTemplate>
            </ItemsControl>
        </StackPanel>
    </StackPanel>
</Window>