Add converters to DatePicker and TimePicker for DateOnly and TimeOnly

src/Controls/src/Core/BindableProperty.cs

@@ -45,7 +45,11 @@ public sealed class BindableProperty
 			{ typeof(Uri), new UriTypeConverter() },
 			{ typeof(Easing), new Maui.Converters.EasingTypeConverter() },
 			{ typeof(Maui.Graphics.Color), new ColorTypeConverter() },
-			{ typeof(ImageSource), new ImageSourceConverter() }
+			{ typeof(ImageSource), new ImageSourceConverter() },
+#if NET6_0_OR_GREATER
+			{ typeof(DateTime), new DateTimeTypeConverter() },
+			{ typeof(TimeSpan), new TimeSpanTypeConverter() }
+#endif
 		};
 
 		internal static readonly Dictionary<Type, IValueConverter> KnownIValueConverters = new Dictionary<Type, IValueConverter>
@@ -269,9 +273,12 @@ internal bool TryConvert(ref object value)
 				value = Convert.ChangeType(value, returnType);
 				return true;
 			}
-			if (KnownTypeConverters.TryGetValue(returnType, out TypeConverter typeConverterTo) && typeConverterTo.CanConvertFrom(valueType))
+
+			Type targetType = Nullable.GetUnderlyingType(returnType) ?? returnType;
+
+			if (KnownTypeConverters.TryGetValue(targetType, out TypeConverter typeConverterTo) && typeConverterTo.CanConvertFrom(valueType))
 			{
-				value = typeConverterTo.ConvertFromInvariantString(value.ToString());
+				value = typeConverterTo.ConvertFromInvariantString(Convert.ToString(value, CultureInfo.InvariantCulture));
 				return true;
 			}
 			if (returnType.IsAssignableFrom(valueType))

src/Controls/src/Core/DateTimeTypeConverter.cs

@@ -0,0 +1,104 @@
+#if NET6_0_OR_GREATER
+using System;
+using System.ComponentModel;
+using System.Globalization;
+using Microsoft.Maui.Controls.Xaml;
+
+namespace Microsoft.Maui.Controls;
+
+internal class DateTimeTypeConverter : TypeConverter
+{
+    public override bool CanConvertFrom(ITypeDescriptorContext? context, Type? sourceType)
+        => sourceType == typeof(DateOnly) || sourceType == typeof(string);
+
+    public override bool CanConvertTo(ITypeDescriptorContext? context, Type? destinationType)
+        => destinationType == typeof(DateTime);
+
+    public override object ConvertFrom(ITypeDescriptorContext? context, CultureInfo? culture, object value)
+    {
+        if (value is DateTime dateTime)
+        {
+            return dateTime;
+        }
+        if (value is DateOnly dateOnly)
+        {
+            return dateOnly.ToDateTime(TimeOnly.MinValue);
+        }
+        if (value is string stringValue)
+        {
+            if (DateOnly.TryParse(stringValue, CultureInfo.InvariantCulture, DateTimeStyles.None, out DateOnly dateTimeOnly))
+            {
+                return dateTimeOnly.ToDateTime(TimeOnly.MinValue);
+            }
+            else if (DateTime.TryParse(stringValue, CultureInfo.InvariantCulture, DateTimeStyles.None, out dateTime))
+            {
+                return dateTime;
+            }
+        }
+
+        throw new NotImplementedException($"Cannot convert \"{value}\" into {typeof(DateTime)}");
+    }
+
+    public override object ConvertTo(ITypeDescriptorContext? context, CultureInfo? culture, object? value, Type? destinationType)
+    {
+        if (value is DateOnly dateOnly)
+        {
+            return ConvertToDestinationType(dateOnly, destinationType, culture);
+        }
+        else if (value is DateTime dateTime)
+        {
+            return ConvertToDestinationType(dateTime, destinationType, culture);
+        }
+        else if (value is string stringValue)
+        {
+            if (DateTime.TryParse(stringValue, CultureInfo.InvariantCulture, DateTimeStyles.None, out dateTime))
+            {
+                return ConvertToDestinationType(dateTime, destinationType, culture);
+            }
+            else if (DateOnly.TryParse(stringValue, CultureInfo.InvariantCulture, out dateOnly))
+            {
+                return ConvertToDestinationType(dateOnly, destinationType, culture);
+            }
+        }
+
+        throw new NotImplementedException($"Cannot convert \"{value}\" into {destinationType}");
+    }
+
+    static object ConvertToDestinationType(DateOnly dateOnly, Type? destinationType, CultureInfo? culture)
+    {
+        if (destinationType == typeof(string))
+        {
+            return dateOnly.ToString( CultureInfo.InvariantCulture);
+        }
+        else if (destinationType == typeof(DateTime))
+        {
+            return dateOnly.ToDateTime(TimeOnly.MinValue);
+        }
+        else if (destinationType == typeof(DateOnly))
+        {
+            return dateOnly;
+        }
+
+        throw new NotImplementedException($"Cannot convert \"{dateOnly}\" into {destinationType}");
+    }
+
+    static object ConvertToDestinationType(DateTime dateTime, Type? destinationType, CultureInfo? culture)
+    {
+        if (destinationType == typeof(string))
+        {
+            return dateTime.ToString(CultureInfo.InvariantCulture);
+        }
+        else if (destinationType == typeof(DateTime))
+        {
+            return dateTime;
+        }
+        else if (destinationType == typeof(DateOnly))
+        {
+            return DateOnly.FromDateTime(dateTime);
+        }
+
+        throw new NotImplementedException($"Cannot convert \"{dateTime}\" into {destinationType}");
+    }
+}
+
+#endif

src/Controls/src/Core/TimeSpanTypeConverter.cs

@@ -0,0 +1,102 @@
+#if NET6_0_OR_GREATER
+using System;
+using System.ComponentModel;
+using System.Globalization;
+using Microsoft.Maui.Controls.Xaml;
+
+namespace Microsoft.Maui.Controls;
+
+internal class TimeSpanTypeConverter : TypeConverter
+{
+    public override bool CanConvertFrom(ITypeDescriptorContext? context, Type? sourceType)
+        => sourceType == typeof(TimeOnly);
+
+    public override bool CanConvertTo(ITypeDescriptorContext? context, Type? destinationType)
+        => destinationType == typeof(TimeSpan);
+
+    public override object ConvertFrom(ITypeDescriptorContext? context, CultureInfo? culture, object value)
+    {
+        if (value is TimeSpan timeSpan)
+        {
+            return timeSpan;
+        }
+        else if (value is TimeOnly timeOnly)
+        {
+            return timeOnly.ToTimeSpan();
+        }
+        else if (value is string stringValue)
+        {
+            if (TimeOnly.TryParse(stringValue, culture, out var timeOnlyResult))
+            {
+                return timeOnlyResult.ToTimeSpan();
+            }
+            else if (TimeSpan.TryParse(stringValue, culture, out var timeSpanResult))
+            {
+                return timeSpanResult;
+            }
+        }
+        throw new NotImplementedException($"Cannot convert \"{value}\" into {typeof(TimeSpan)}");
+    }
+
+    public override object ConvertTo(ITypeDescriptorContext? context, CultureInfo? culture, object? value, Type? destinationType)
+    {
+        if (value is TimeSpan timeSpan)
+        {
+            return ConvertToDestinationType(timeSpan, destinationType, culture);
+        }
+        else if (value is TimeOnly timeOnly)
+        {
+            return ConvertToDestinationType(timeOnly, destinationType, culture);
+        }
+        else if (value is string stringValue)
+        {
+            if (TimeOnly.TryParse(stringValue, culture, out timeOnly))
+            {
+                return ConvertToDestinationType(timeOnly, destinationType, culture);
+            }
+            else if (TimeSpan.TryParse(stringValue, culture, out var timeSpan1))
+            {
+                return ConvertToDestinationType(timeSpan1, destinationType, culture);
+            }
+        }
+
+        throw new NotImplementedException($"Cannot convert \"{value}\" into {destinationType}");
+    }
+
+    static object ConvertToDestinationType(TimeOnly timeOnly, Type? destinationType, CultureInfo? culture)
+    {
+        if (destinationType == typeof(string))
+        {
+            return timeOnly.ToString(culture);
+        }
+        else if (destinationType == typeof(TimeSpan))
+        {
+            return timeOnly.ToTimeSpan();
+        }
+        else if (destinationType == typeof(TimeOnly))
+        {
+            return timeOnly;
+        }
+
+        throw new NotImplementedException($"Cannot convert \"{timeOnly}\" into {destinationType}");
+    }
+
+    static object ConvertToDestinationType(TimeSpan timeSpan, Type? destinationType, CultureInfo? culture)
+    {
+        if (destinationType == typeof(string))
+        {
+            return timeSpan.ToString();
+        }
+        else if (destinationType == typeof(TimeSpan))
+        {
+            return timeSpan;
+        }
+        else if (destinationType == typeof(TimeOnly))
+        {
+            return TimeOnly.FromTimeSpan(timeSpan);
+        }
+
+        throw new NotImplementedException($"Cannot convert \"{timeSpan}\" into {destinationType}");
+    }
+}
+#endif

src/Controls/tests/Core.UnitTests/DateOnlyTypeConverterTests.cs

@@ -0,0 +1,73 @@
+#if NET6_0_OR_GREATER
+
+namespace Microsoft.Maui.Controls.Core.UnitTests;
+
+using System;
+using System.ComponentModel;
+using System.Globalization;
+using System.Threading.Tasks;
+using Xunit;
+
+public class DateOnlyTypeConverterTests : BaseTestFixture
+{
+	[Fact]
+	public void DateOnlyToDateTimeConversion()
+	{
+		var converter = new DateTimeTypeConverter();
+
+		var dateOnlyValue = new DateOnly(2025, 2, 21);
+
+		var actualDateTime = converter.ConvertFrom(null, CultureInfo.InvariantCulture, dateOnlyValue);
+		var expectedDateTime = new DateTime(2025, 2, 21);
+
+		Assert.Equal(expectedDateTime, actualDateTime);
+	}
+
+	[Fact]
+	public void DateTimeToDateOnlyConversion()
+	{
+		var converter = new DateTimeTypeConverter();
+
+		var dateTimeValue = new DateTime(2025, 2, 21);
+
+		var actualDateOnly = converter.ConvertTo(null, CultureInfo.InvariantCulture, dateTimeValue, typeof(DateOnly));
+		var expectedDateOnly = new DateOnly(2025, 2, 21);
+
+		Assert.Equal(expectedDateOnly, actualDateOnly);
+	}
+
+	[Fact]
+	public void DateOnlyToDatePickerBinding()
+	{
+		var datePicker = new DatePicker();
+		var source = new Issue20438DatePickerViewModel
+		{
+			SelectedDate = new DateOnly(2025, 3, 15)
+		};
+		datePicker.BindingContext = source;
+		datePicker.SetBinding(DatePicker.DateProperty, "SelectedDate");
+		var expectedDateTime = new DateTime(2025, 3, 15);
+		Assert.Equal(expectedDateTime, datePicker.Date);
+	}
+
+	[Fact]
+	public void DateOnlyToNonNullableBinding()
+	{
+		var dateProperty = BindableProperty.Create("Date", typeof(DateTime), typeof(DatePicker), null, BindingMode.TwoWay);
+		var source = new Issue20438DatePickerViewModel
+		{
+			SelectedDate = new DateOnly(2025, 3, 15)
+		};
+		var bo = new MockBindable { BindingContext = source };
+
+		bo.SetBinding(dateProperty, "SelectedDate");
+		var expectedDateTime = new DateTime(2025, 3, 15);
+		Assert.Equal(expectedDateTime, bo.GetValue(dateProperty));
+	}
+
+	public class Issue20438DatePickerViewModel
+	{
+		public DateOnly SelectedDate { get; set; }
+	}
+}
+#endif

src/Controls/tests/Core.UnitTests/TimeOnlyTypeConverterTests.cs

@@ -0,0 +1,72 @@
+#if NET6_0_OR_GREATER
+
+namespace Microsoft.Maui.Controls.Core.UnitTests;
+
+using System;
+using System.Globalization;
+using System.Threading.Tasks;
+using Xunit;
+
+public class TimeOnlyTypeConverterTests : BaseTestFixture
+{
+	[Fact]
+	public void TimeOnlyToTimeSpanConversion()
+	{
+		var converter = new TimeSpanTypeConverter();
+
+		var timeOnlyValue = new TimeOnly(8, 30, 0);
+
+		var actualTimeSpan = converter.ConvertFrom(null, CultureInfo.InvariantCulture, timeOnlyValue);
+		var expectedTimeSpan = new TimeSpan(8, 30, 0);
+
+		Assert.Equal(expectedTimeSpan, actualTimeSpan);
+	}
+
+	[Fact]
+	public void TimeSpanToTimeOnlyConversion()
+	{
+		var converter = new TimeSpanTypeConverter();
+
+		var timeSpanValue = new TimeSpan(8, 30, 0);
+
+		var actualTimeOnly = converter.ConvertTo(null, CultureInfo.InvariantCulture, timeSpanValue, typeof(TimeOnly));
+		var expectedTimeOnly = new TimeOnly(8, 30, 0);
+
+		Assert.Equal(expectedTimeOnly, actualTimeOnly);
+	}
+
+	[Fact]
+	public void TimeOnlyToTimePickerBinding()
+	{
+		var timePicker = new TimePicker();
+		var source = new Issue20438TimePickerViewModel
+		{
+			SelectedTime = new TimeOnly(14, 30, 0)
+		};
+		timePicker.BindingContext = source;
+		timePicker.SetBinding(TimePicker.TimeProperty, "SelectedTime");
+		var expectedTimeSpan = new TimeSpan(14, 30, 0);
+		Assert.Equal(expectedTimeSpan, timePicker.Time);
+	}
+
+	[Fact]
+	public void TimeOnlyToNonNullableBinding()
+	{
+		var timeProperty = BindableProperty.Create("Time", typeof(TimeSpan), typeof(TimePicker), null, BindingMode.TwoWay);
+		var source = new Issue20438TimePickerViewModel
+		{
+			SelectedTime = new TimeOnly(14, 30, 0)
+		};
+		var bo = new MockBindable { BindingContext = source };
+
+		bo.SetBinding(timeProperty, "SelectedTime");
+		var expectedTimeSpan = new TimeSpan(14, 30, 0);
+		Assert.Equal(expectedTimeSpan, bo.GetValue(timeProperty));
+	}
+
+	public class Issue20438TimePickerViewModel
+	{
+		public TimeOnly SelectedTime { get; set; }
+	}
+}
+#endif