WPF UserControl using MVVMLight can't find ViewModelLocator

Question

I've got two problems. I have a WPF UserControl that is a .dll plugin to another WPF application.

The first is, unless I install MVVMLight in the WPF application that is using my Usercontrol dll, it complains it can't find any MVVMLight libraries. Is there anyway I don't have to install MVVMLight on the Main WPF application using my UserControl dll?

Second is, it can't find the ViewModelLocator in my UserControl. I've tried making it a StaticResource of my UserControl but it can't find the ViewModelLocator.

Please help.

Answer 1

Here is an example on how to use a View Model Locator:

Start with a simple ViewModel:

public class MainViewModel
{
    public string TestProperty { get; set; } = "ViewModelLocator works fine!";
}

Define the ViewModelLocator:

public class ViewModelLocator
{
    private static readonly MainViewModel mainViewModel;

    static ViewModelLocator()
    {
        mainViewModel = new MainViewModel();
    }

    public static MainViewModel MainViewModel => mainViewModel;
}

As you see, your ViewModel's instance is created only once in the static constructor, and after that, the same instance is returned.

And here is the View:

<Window x:Class="SetViewModelLocator.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:local="clr-namespace:SetViewModelLocator"
    xmlns:vm="clr-namespace:SetViewModelLocator.ViewModels"
    mc:Ignorable="d"
    Title="MainWindow" Height="350" Width="525">
<Window.Resources>
    <vm:ViewModelLocator x:Key="ViewModelLocator"/>
</Window.Resources>
<Grid DataContext="{Binding Source={StaticResource ViewModelLocator}, Path=MainViewModel}">
    <TextBlock Text="{Binding TestProperty}"/>
</Grid>

Set the Locator as a Resource and use it as the DataContext of your main container which in this case is a Grid.