InitializeComponent fires StackOverflow Exception when binding

Question

Trying to understand data binding and this totally seems like a rookie mistake but I have no idea why it's happening.

CS

namespace MuhProgram
{
    public partial class MainWindow : Window
    {
        public string foobar
        {
            get { return "loremipsum"; }
        }

        public MainWindow()
        {
            InitializeComponent();
        }
    }
}

XAML:

<Window x:Class="MuhProgram.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:MuhProgram"
        Title="MainWindow" Height="350" Width="525">

    <Window.Resources>
         <local:MainWindow x:Key="classMainWindow"/>
    </Window.Resources>

    <Grid>
        <Label Content="{Binding Source={StaticResource classMainWindow}, Path=foobar}"></Label>
    </Grid>
</Window>

Debugger points at InitializeComponent() call in MainWindow() method with StackOverflowException.

I also tried setting DataContext attribute to "{StaticResource classMainWindow}" in the grid but the effect is the same.

Rohit Vats · Accepted Answer · 2014-10-03 08:18:05Z

7

StackOverflow exception is raised because you are recursively creating an instance of MainWindow at this line

<local:MainWindow x:Key="classMainWindow"/>

When InitializeComponent() gets called, it will initialize the XAML and load it from compiled BAML. While loading it found Label Content needs another instance of MainWindow to bind it's Content DP. Hence, it will create MainWindow recursively until it crashes with SO exception.

You don't need to declare another instance of MainWindow. Bind Label to parent instance like this:

<Label Content="{Binding Path=foobar, RelativeSource={RelativeSource FindAncestor, 
                                                            AncestorType=Window}}"/>

OR

Either set DataContext to itself and let Label inherit it from parent window.

<Window DataContext="{Binding RelativeSource={RelativeSource Self}}">
  ....
  <Label Content="{Binding foobar}"/>

OR

Set x:Name on window and bind using ElementName.

<Window x:Name="myWindow">
   .....
   <Label Content="{Binding foobar, ElementName=myWindow}" />

edited Oct 3, 2014 at 8:18

answered Oct 3, 2014 at 8:10

Rohit Vats

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4 Comments

matt-pielat Over a year ago

What do you mean "declare another instance of MainWindow"? Where am I doing that?

Rohit Vats Over a year ago

Here you are declaring another instance <local:MainWindow x:Key="classMainWindow"/>.

matt-pielat Over a year ago

Is this why I'm getting a stack overflow? The guy here is doing the very same thing (first XAML code snippet).

Rohit Vats Over a year ago

I have added more details to the answer. In the posted link, they are creating instance of another class and not of itself. Generally it is used to create instance of ViewModel.

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