WPF bind usercontrol to viewmodel from code behind

Question

Mainwindow constructor:

InitializeComponent();
MainViewModel = new MainViewModel();
captureUserControl.DataContext = MainViewModel.CaptureViewModel;

XAML in mainwindow

<UserControls:CaptureControl x:Name="captureUserControl"/>

Part of usercontrol

<Image x:Name="masterImage"  Margin="0,189,0,120" RenderTransformOrigin="0.5,0.5" Source="{Binding Path=MasterImage, ElementName=captureUserControl}" Stretch="Fill" Grid.Column="1" >

Part of ViewModel

public BitmapSource MasterImage { get { return masterImage; } private set {SetValue<BitmapSource>(ref masterImage, value); } }

Error

System.Windows.Data Error: 40 : BindingExpression path error: 
'MasterImage' property not found on 'object' ''CaptureControl' 
(Name='captureUserControl')'. BindingExpression:Path=MasterImage; 
DataItem='CaptureControl' (Name='captureUserControl'); 
target element is 'Image' (Name='masterImage'); target property is 'Source' (type 'ImageSource')

I think it might be because on creation the captureUserControl doesn't have its datacontext set until after its created. I want the MainViewModel to be instantiated in code behind because there's stuff that needs to be done that isn't a button click for example. Certain async methods need to be called on window load to initialize hardware. Does anyone have any examples or tips of the data bindings set up in this way?

The DataContext of an element is inherited by it's children. Did you try without the ElementName in you usercontrol's binding ? A maybe related question : http://stackoverflow.com/questions/7262137/what-is-datacontext-for — Irwene, Apr 17 '15 at 17:48

score 1 · Accepted Answer · edited May 23 '17 at 12:06

1

The DataContext of an element is inherited by it's children.

The solution here is to remove ElementName from the Binding

A link for more details about DataContexts : What is DataContext for?

edited May 23 '17 at 12:06

Community

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answered Apr 17 '15 at 18:13

Irwene

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score 0 · Answer 2 · answered Apr 17 '15 at 18:14

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UserControls were not designed to be bound to view-models.

They were meant to be bound to other containers (i.e. Window).

answered Apr 17 '15 at 18:14

Scott Nimrod

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WPF bind usercontrol to viewmodel from code behind

2 Answers2