Window height and width binding: Only one is fetched from DataContext

Question

I've been googling this without getting the issue of that:

Simple xaml:

<Window x:Class="WpfHeightBinding.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:wpfHeightBinding="clr-namespace:WpfHeightBinding"
        Title="MainWindow" 
        Width="{Binding Width}"
        Height="{Binding Height}"
        SizeToContent="Manual"
        >
    <Window.DataContext>
        <wpfHeightBinding:TheDataContext />
    </Window.DataContext>
    <Grid>
    </Grid>
</Window>

I bind both Width and Height to the data context. Here's the cs code

using System.Windows;

namespace WpfHeightBinding
{
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }
    }

    public class TheDataContext
    {
        public int Width
        {
            get { return 200; }
        }

        public int Height
        {
            get { return 400; }
        }
    }
}

I set breakpoints to both getters. Only the first one is fetched, Height is ignored. If I switch Height and Width in xaml, then only the Height is fetched and Width is ignored.

I really cannot explain this behaviour. The window's height seems to be arbitrary. I have no MinHeight, nothing else influencing it, what happens to the binding? There is no error. SizeToContent has no effect.

I would understand if none of them are used as they might have been fetched before DataContext has been initialized but the DataContext is queried.

please check this link if it help http://stackoverflow.com/questions/2673600/problems-with-binding-to-window-height-and-width — Vinkal, Feb 21 '15 at 19:24

score 2 · Answer 1 · answered Feb 26 '15 at 15:07

You need to give your 'Width' and 'Height' properties setters in code-behind - and then make your bindings 'TwoWay':

XAML

<Window x:Class="WpfHeightBinding.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:wpfHeightBinding="clr-namespace:WpfHeightBinding"
    Title="MainWindow" 
    Width="{Binding Width, Mode=TwoWay}"
    Height="{Binding Height, Mode=TwoWay}"
    SizeToContent="Manual"        
    >
<Window.DataContext>
    <wpfHeightBinding:TheDataContext />
</Window.DataContext>

Code-behind:

public class TheDataContext
{
    public int Width { get { return 800; } set { } }
    public int Height { get { return 200; } set { } }
}

A possible alternate may be to use a `OneTime` binding... I'm not sure, I've never tested it. — Rachel, Feb 26 '15 at 16:35

Window height and width binding: Only one is fetched from DataContext

1 Answers1