[Enhancement] DatePicker and TimePicker should support DateOnly? and TimeOnly?

Merging #1847

Summary

• DatePicker and TimePicker should use the new DateOnly and TimeOnly structs instead of DateTime
• The new fields should be nullable
• The new fields should be added to the Core implementation of MAUI
• The old properties should continue to exist in Controls, be marked as Obsolete, and wrap the new properties from Core

API Proposed:

Core:

public partial interface IDatePicker
{ 
  DateOnly? Value { get; set; }
  
  DateOnly? MinimumValue { get; }
  
  DateOnly? MaximumValue { get; }
}

public partial interface ITimePicker
{ 
  TimeOnly? Value { get; }
}

Controls:

public partial class DatePicker
{ 
  DateOnly? Value { get; set; }
  
  DateOnly? MinimumValue { get; set; }
  
  DateOnly? MaximumValue { get; set; }

  [Obsolete($"Use {nameof(Value)} instead.")]
  DateTime Date
  {
    get => Value?.ToDateTime(TimeOnly.MinValue) ?? DateTime.MinValue;
    set => Value = DateOnly.FromDateTime(value);
  }

  [Obsolete($"Use {nameof(MinimumValue)} instead.")]
  DateTime MinimumDate
  {
    get => MinimumValue?.ToDateTime(TimeOnly.MinValue) ?? DateTime.MinValue;
    set => MinimumValue = DateOnly.FromDateTime(value);
  }

  [Obsolete($"Use {nameof(MaximumValue)} instead.")]
  DateTime MaximumDate
  {
    get => MaximumValue?.ToDateTime(TimeOnly.MinValue) ?? DateTime.MinValue;
    set => MaximumValue = DateOnly.FromDateTime(value);
  }
}

public partial class TimePicker
{ 
  TimeOnly? Value { get; set; }

  [Obsolete($"Use {nameof(Value)} instead.")]
  TimeSpan Time
  {
    get => Value?.ToTimeSpan() ?? TimeSpan.Zero;
    set => Value = TimeOnly.FromTimeSpan(value);
  }
}

ORIGINAL POST:

Summary

I wish DatePicker had a Date property that was nullable, so that we could use it for optional dates.

API Changes

My suggestion is to follow how UWP/WinUI resolved this issue in a backward-compatible way: They added another property.

public System.DateOnly? SelectedDate { get; set; }

It would go in both DatePicker and IDatePicker (which doesn’t need to be back-compat).

By the way, I used the new DateOnly instead of DateTime. But I’m fine if that’s not feasible.

Intended Use Case

Currently, it is a pain to build an app that allows users to provide an optional date. One workaround is to add a checkbox to “activate” entering that date, but that is really not user-friendly.

[msftbot[bot]]

We’ve moved this issue to the Backlog milestone. This means that it is not going to be worked on for the coming release. We will reassess the backlog following the current release and consider this item at that time. To learn more about our issue management process and to have better expectation regarding different types of issues you can read our Triage Process.

[KPixel]

@rmarinho @hartez @Redth Please, let’s not forget about this issue.

After MAUI goes into RC, you will probably consider this change as breaking, and at that time, it will be impossible to add.