👀 Views: 72 💬 Answers: 1 📅 Created: 2025-06-09

wpf data-binding visual-studio mvvm C#

I'm working with an scenario in my WPF application where I'm getting an 'Object reference not set to an instance of an object' exception when trying to bind a property to a ComboBox... The ComboBox is supposed to display a list of items from my ViewModel, but during runtime, it throws this behavior and doesn't show any items. Here’s a simplified version of my ViewModel: ```csharp public class MyViewModel : INotifyPropertyChanged { private ObservableCollection<string> _items; public ObservableCollection<string> Items { get { return _items; } set { _items = value; OnPropertyChanged(); } } public MyViewModel() { // Trying to populate Items here Items = new ObservableCollection<string>(); // This works fine LoadItems(); } private void LoadItems() { // Simulating data loading Items.Add("Item 1"); Items.Add("Item 2"); } } ``` And in my XAML file, I have: ```xml <Window x:Class="MyApp.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="MainWindow" Height="350" Width="525"> <Grid> <ComboBox ItemsSource="{Binding Items}" /> </Grid> </Window> ``` In the code-behind, I've set the DataContext like this: ```csharp public MainWindow() { InitializeComponent(); DataContext = new MyViewModel(); } ``` Despite following this setup, the application throws the exception when the ComboBox tries to bind to `Items`. I’ve also tried implementing a basic behavior handling in my ViewModel, but that hasn’t helped. I suspect it might be related to the timing of the data binding or the data context being null at some point. Could anyone provide insights or best practices to debug this scenario? Thanks! This is part of a larger CLI tool I'm building. I'm working with C# in a Docker container on Windows 10. Could this be a known issue? This issue appeared after updating to C# 3.10. I'm open to any suggestions.