How do I set a ViewModel on a window in XAML using DataContext property?
.NetWpfXamlMvvm.Net Problem Overview
The question pretty much says it all.
I have a window, and have tried to set the DataContext using the full namespace to the ViewModel, but I seem to be doing something wrong.
<Window x:Class="BuildAssistantUI.BuildAssistantWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
DataContext="BuildAssistantUI.ViewModels.MainViewModel">
.Net Solutions
Solution 1 - .Net
Try this instead.
<Window x:Class="BuildAssistantUI.BuildAssistantWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:VM="clr-namespace:BuildAssistantUI.ViewModels">
<Window.DataContext>
<VM:MainViewModel />
</Window.DataContext>
</Window>
Solution 2 - .Net
In addition to the solution that other people provided (which are good, and correct), there is a way to specify the ViewModel in XAML, yet still separate the specific ViewModel from the View. Separating them is useful for when you want to write isolated test cases.
In App.xaml:
<Application
x:Class="BuildAssistantUI.App"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:BuildAssistantUI.ViewModels"
StartupUri="MainWindow.xaml"
>
<Application.Resources>
<local:MainViewModel x:Key="MainViewModel" />
</Application.Resources>
</Application>
In MainWindow.xaml:
<Window x:Class="BuildAssistantUI.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
DataContext="{StaticResource MainViewModel}"
/>
Solution 3 - .Net
You need to instantiate the MainViewModel and set it as datacontext. In your statement it just consider it as string value.
<Window x:Class="BuildAssistantUI.BuildAssistantWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:BuildAssistantUI.ViewModels">
<Window.DataContext>
<local:MainViewModel/>
</Window.DataContext>
Solution 4 - .Net
There is also this way of specifying the viewmodel:
using Wpf = System.Windows;
public partial class App : Wpf.Application //your skeleton app already has this.
{
protected override void OnStartup( Wpf.StartupEventArgs e ) //you need to add this.
{
base.OnStartup( e );
MainWindow = new MainView();
MainWindow.DataContext = new MainViewModel( e.Args );
MainWindow.Show();
}
}
<Rant>
All of the solutions previously proposed require that MainViewModel
must have a parameterless constructor.
Microsoft is under the impression that systems can be built using parameterless constructors. If you are also under that impression, go ahead and use some of the other solutions.
For those that know that constructors must have parameters, and therefore the instantiation of objects cannot be left in the hands of magic frameworks, the proper way of specifying the viewmodel is the one I showed above.
</Rant>
Solution 5 - .Net
You might want to try Catel. It allows you to define a DataWindow
See this article for an example.