Null check for autocomplete box

[AmeerMansour]

Bug explanation

I start type in the autocomplete boxthen when I select one of the suggestions it crashes
this is my xmal

and it crash here for nor selecteditem being null

Version

5.1

[corvinsz]

@AmeerMansour I can't reproduce your problem. Can you share more information about your project and/or check if you have implemented the AutoSuggestBox correctly?
Here is a minimal setup to get the AutoSuggestBox to work:

<Window x:Class="MDIX3741.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:local="clr-namespace:MDIX3741"
        xmlns:materialDesign="http://materialdesigninxaml.net/winfx/xaml/themes"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        Title="MainWindow"
        Width="800"
        Height="450"
        Style="{StaticResource MaterialDesignWindow}"
        mc:Ignorable="d">
    <materialDesign:AutoSuggestBox Margin="5"
                                   VerticalAlignment="Center"
                                   materialDesign:HintAssist.Hint="Value"
                                   materialDesign:TextFieldAssist.HasClearButton="True"
                                   Style="{StaticResource MaterialDesignOutlinedAutoSuggestBox}"
                                   Suggestions="{Binding Suggestions}"
                                   Text="{Binding MyValue, UpdateSourceTrigger=PropertyChanged}">

        <materialDesign:AutoSuggestBox.ItemTemplate>
            <DataTemplate>
                <TextBlock Text="{Binding .}" />
            </DataTemplate>
        </materialDesign:AutoSuggestBox.ItemTemplate>
    </materialDesign:AutoSuggestBox>
</Window>

Code behind:

public partial class MainWindow : Window
{
	public MainWindow()
	{
		InitializeComponent();
		this.DataContext = new MainViewModel();
	}
}

public partial class MainViewModel : ObservableObject
{
	private static readonly List<string> _allSuggestions = ["1", "11", "112", "1333", "444"];

	[ObservableProperty]
	private string _myValue;

	partial void OnMyValueChanged(string value)
	{
		if (string.IsNullOrEmpty(value))
		{
			Suggestions = _allSuggestions;
			return;
		}

		Suggestions = _allSuggestions.Where(x => x.Contains(value, StringComparison.InvariantCultureIgnoreCase))
									.ToList();
	}

	private IReadOnlyList<string> _suggestions;
	public IReadOnlyList<string> Suggestions
	{
		get => _suggestions;
		set => SetProperty(ref _suggestions, value);
	}
}

Make sure to install the CommunityToolkit.Mvvm to get this code to work.