(WinUI) DatePicker SelectedDate Binding null issue (x:Bind and Binding are different results)

Question

(WInUI3) DatePicker SelectedDate x:Bind and Binding are different results ?? x:Bind => SelectedDate is null Binding => SelectedDate is 1923-1-1

Result Image :

How to do let binding is also null ?

Code :

<DatePicker SelectedDate="{x:Bind vm.MyDate, Mode=TwoWay}"/>
<StackPanel DataContext="{x:Bind vm}">
   <DatePicker SelectedDate="{Binding MyDate}"/>
</StackPanel>

public class MyTable : ObservableObject
{
    private DateTimeOffset? _mydate;
    public DateTimeOffset? MyDate
    {
        get => _mydate;
        set => SetProperty(ref _mydate, value);
    }
}

public sealed partial class MainWindow : Window
{
    MyTable vm = new MyTable();
    public MainWindow() { this.InitializeComponent(); }
}

Andrew KeepCoding · Accepted Answer · 2023-05-09 06:24:01Z

2

It seems that Binding doesn't pass the null value and converts it to some default value. This might be because DateTimeOffset is a struct.

Anyhow, here's a workaround creating a custom control:

public class CustomDatePicker : DatePicker
{
    public CustomDatePicker()
    {
        this.RegisterPropertyChangedCallback(DatePicker.SelectedDateProperty, OnSelectedDatePropertyChanged);
    }

    private void OnSelectedDatePropertyChanged(DependencyObject sender, DependencyProperty dp)
    {
        if (this.SelectedDate <= this.MinYear)
        {
            this.SelectedDate = null;
        }
    }
}

It works with both Binding and x:Bind:

<local:CustomDatePicker SelectedDate="{x:Bind ViewModel.MyDate, Mode=TwoWay}" />
<StackPanel DataContext="{x:Bind ViewModel}">
    <local:CustomDatePicker SelectedDate="{Binding MyDate, Mode=TwoWay}" />
</StackPanel>

answered May 9, 2023 at 6:24

Andrew KeepCoding

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Andrew KeepCoding Over a year ago

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