You're trying to do a very strange trick, which is not supposed to work. Try to make the following changes.
MainWindow.xaml.cs -- try to always keep you code-behind clear.
namespace WpfTryIt
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}
}
}
MainWindow.xaml
<Window x:Class="WpfTryIt.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow"
xmlns:s ="clr-namespace:WpfTryIt"
>
<Window.DataContext>
<s:FakeDataContext></s:FakeDataContext>
</Window.DataContext>
<Button Content="{Binding Path=BindingHeight}"/>
</Window>
And a new separate data context class, which behave different depending on the mode:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.ComponentModel;
using System.Windows;
namespace WpfTryIt
{
public class FakeDataContext
{
public int BindingHeight
{
get
{
// Check for design mode.
if ((bool)(DesignerProperties.IsInDesignModeProperty.GetMetadata(typeof(DependencyObject)).DefaultValue))
{
//in Design mode
return 100;
}
else
{
return 200;
}
}
}
}
}