Error: "Unable to find a setter that allows multiple assignments to the property DataContext of type ..."

[AlanPBourke]

MainWindow.axaml is below, there is only one child element. DataContext is set to MainWindowViewModel in App.xaml.cs.

<Window
    x:Class="AvaloniaTest2.Views.MainWindow"
    xmlns="https://github.com/avaloniaui"
    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:vm="using:AvaloniaTest2.ViewModels"
    Title="AvaloniaTest2"
    d:DesignHeight="450"
    d:DesignWidth="800"
    Icon="/Assets/avalonia-logo.ico"
    mc:Ignorable="d">

    <Design.DataContext>
        This only sets the DataContext for the previewer in an IDE,
        to set the actual DataContext for runtime, set the DataContext property in code (look at App.axaml.cs)
        <vm:MainWindowViewModel />
    </Design.DataContext>

    <StackPanel>
        <DataGrid Name="CustomerList" Items="{Binding CustomerList}" />
    </StackPanel>

</Window>

MainWindowViewModel.cs

using AvaloniaTest2.Interfaces;
using System.Collections.ObjectModel;

namespace AvaloniaTest2.ViewModels;
public class MainWindowViewModel : ViewModelBase
{
    public ObservableCollection<CustomerViewModel> CustomerList { get; } = new();
    private IDataProvider DataProvider;

    public MainWindowViewModel()
    {
        DataProvider = new SqlServerDataProvider();
        var all = DataProvider.Customers.GetAll();
        foreach (var c in all)
        {
            CustomerList.Add(new CustomerViewModel { Code = c.Code, Name = c.Name });
        }
    }
}

I can't figure out where that error is coming from.

[AlanPBourke]

The issue is of course the word 'DataContext' in the boilerplate 'This only sets ...' comment in the XAML being picked up by the compiler, d'oh ...

[sedwick2048]

This got me too. Why is little crap like this so easy to miss sometimes?

[timunie]

It's a comment and must be but looks like it was uncommented in the original screenshot by accident.

[AlanPBourke]

Two of us didn't uncomment it by accident. The boilerplate seems to have been fixed since the original issue.