Fix DatePicker CharacterSpacing property not working on Windows platform

src/Controls/tests/TestCases.HostApp/Issues/Issue30066.cs

@@ -0,0 +1,63 @@
+using Microsoft.Maui.Controls;
+using System;
+
+namespace Maui.Controls.Sample.Issues;
+
+[Issue(IssueTracker.Github, "30066", "DatePicker CharacterSpacing Property Not Working on Windows", PlatformAffected.UWP)]
+public class Issue30066 : TestShell
+{
+	protected override void Init()
+	{
+		var shellContent = new ShellContent
+		{
+			Title = "DatePicker CharacterSpacing Test",
+			Content = new Issue30066ContentPage() { Title = "DatePicker CharacterSpacing Test" }
+		};
+
+		Items.Add(shellContent);
+	}
+
+	class Issue30066ContentPage : ContentPage
+	{
+		public Issue30066ContentPage()
+		{
+			var datePicker = new DatePicker
+			{
+				Date = DateTime.Today,
+				CharacterSpacing = 10,
+				AutomationId = "TestDatePicker",
+				HorizontalOptions = LayoutOptions.Center,
+				VerticalOptions = LayoutOptions.Center,
+			};
+
+			var label = new Label
+			{
+				Text = "The DatePicker above should have character spacing of 10 applied to its text.",
+				HorizontalOptions = LayoutOptions.Center,
+				Margin = new Thickness(20),
+				HorizontalTextAlignment = TextAlignment.Center
+			};
+
+			var button = new Button
+			{
+				Text = "Change Character Spacing to 20",
+				AutomationId = "ChangeSpacingButton",
+				HorizontalOptions = LayoutOptions.Center,
+				Margin = new Thickness(0, 20)
+			};
+
+			button.Clicked += (s, e) =>
+			{
+				datePicker.CharacterSpacing = datePicker.CharacterSpacing == 10 ? 20 : 10;
+				button.Text = $"Change Character Spacing to {(datePicker.CharacterSpacing == 10 ? 20 : 10)}";
+			};
+
+			Content = new StackLayout
+			{
+				Children = { datePicker, label, button },
+				Spacing = 20,
+				Margin = new Thickness(20)
+			};
+		}
+	}
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue30066.cs

@@ -0,0 +1,40 @@
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues;
+
+public class Issue30066 : _IssuesUITest
+{
+	public Issue30066(TestDevice device)
+		: base(device)
+	{
+	}
+
+	public override string Issue => "DatePicker CharacterSpacing Property Not Working on Windows";
+
+	[Test]
+	[Category(UITestCategories.DatePicker)]
+	public void DatePickerCharacterSpacingShouldApply()
+	{
+		App.WaitForElement("TestDatePicker");
+
+		// Take a screenshot to verify character spacing is applied
+		// On Windows, the DatePicker text should show increased character spacing
+		VerifyScreenshot();
+	}
+
+	[Test]
+	[Category(UITestCategories.DatePicker)]
+	public void DatePickerCharacterSpacingCanChange()
+	{
+		App.WaitForElement("TestDatePicker");
+		App.WaitForElement("ChangeSpacingButton");
+
+		// Change the character spacing by clicking the button
+		App.Tap("ChangeSpacingButton");
+
+		// Take a screenshot to verify the character spacing changed
+		VerifyScreenshot();
+	}
+}

src/Core/src/Platform/Windows/CharacterSpacingExtensions.cs

@@ -8,5 +8,21 @@ public static int ToEm(this double pt)
 		{
 			return Convert.ToInt32(pt * 0.0624f * 1000); // Coefficient for converting Pt to Em. The value is uniform spacing between characters, in units of 1/1000 of an em.
 		}
+
+		/// <summary>
+		/// Converts character spacing from Em units back to the original double value.
+		/// </summary>
+		/// <param name="emValue">The character spacing value in Em units (1/1000 of an em)</param>
+		/// <returns>The original character spacing value in points</returns>
+		/// <remarks>
+		/// This method performs the inverse operation of ToEm().
+		/// Em units are defined as 1/1000 of an em, where the conversion coefficient is 0.0624.
+		/// The calculation reverses: originalValue * 0.0624 * 1000 = emValue
+		/// So: originalValue = emValue / (0.0624 * 1000)
+		/// </remarks>
+		public static double FromEm(this int emValue)
+		{
+			return emValue / (0.0624 * 1000);
+		}
 	}
 }

src/Core/src/Platform/Windows/DatePickerExtensions.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Linq;
 using Microsoft.Maui.Graphics;
 using Microsoft.UI.Xaml.Controls;
 using WBrush = Microsoft.UI.Xaml.Media.Brush;
@@ -38,7 +39,34 @@ public static void UpdateMaximumDate(this CalendarDatePicker platformDatePicker,
 
 		public static void UpdateCharacterSpacing(this CalendarDatePicker platformDatePicker, IDatePicker datePicker)
 		{
-			platformDatePicker.CharacterSpacing = datePicker.CharacterSpacing.ToEm();
+			// Store the character spacing value to apply it when ready
+			var characterSpacing = datePicker.CharacterSpacing;
+
+			// Apply immediately if loaded, otherwise wait for load
+			if (platformDatePicker.IsLoaded)
+			{
+				ApplyCharacterSpacingToTextBlocks(platformDatePicker, characterSpacing);
+			}
+			else
+			{
+				// Wait for the control to load, then apply character spacing
+				platformDatePicker.OnLoaded(() => ApplyCharacterSpacingToTextBlocks(platformDatePicker, characterSpacing));
+			}
+		}
+
+		static void ApplyCharacterSpacingToTextBlocks(CalendarDatePicker platformDatePicker, double characterSpacing)
+		{
+			// Find all TextBlock elements within the CalendarDatePicker and apply character spacing
+			var textBlocks = platformDatePicker.GetChildren<Microsoft.UI.Xaml.Controls.TextBlock>();
+			var characterSpacingEm = characterSpacing.ToEm();
+
+			foreach (var textBlock in textBlocks)
+			{
+				if (textBlock is not null)
+				{
+					textBlock.CharacterSpacing = characterSpacingEm;
+				}
+			}
 		}
 
 		public static void UpdateFont(this CalendarDatePicker platformDatePicker, IDatePicker datePicker, IFontManager fontManager) =>

src/Core/src/PublicAPI/net-windows/PublicAPI.Unshipped.txt

@@ -1 +1,2 @@
 #nullable enable
+static Microsoft.Maui.Platform.CharacterSpacingExtensions.FromEm(this int emValue) -> double

src/Core/tests/DeviceTests/Handlers/DatePicker/DatePickerHandlerTests.Windows.cs

@@ -2,6 +2,7 @@
 using System.Threading.Tasks;
 using Microsoft.Maui.Controls;
 using Microsoft.Maui.DeviceTests.Stubs;
+using Microsoft.Maui.Platform;
 using Microsoft.UI.Xaml.Controls;
 using Xunit;
 
@@ -89,5 +90,53 @@ Color GetNativeTextColor(DatePickerHandler datePickerHandler)
 
 			return null;
 		}
+
+		[Fact]
+		public async Task CharacterSpacingInitializesCorrectly()
+		{
+			var datePicker = new DatePickerStub()
+			{
+				Date = DateTime.Today,
+				CharacterSpacing = 10
+			};
+
+			await ValidatePropertyInitValue(datePicker, () => datePicker.CharacterSpacing, GetNativeCharacterSpacing, 10.0);
+		}
+
+		double GetNativeCharacterSpacing(DatePickerHandler datePickerHandler)
+		{
+			var platformDatePicker = GetNativeDatePicker(datePickerHandler);
+
+			// Since CalendarDatePicker doesn't have CharacterSpacing property directly,
+			// we need to check if it was applied to internal TextBlock elements
+			var textBlocks = platformDatePicker.GetChildren<Microsoft.UI.Xaml.Controls.TextBlock>();
+			foreach (var textBlock in textBlocks)
+			{
+				if (textBlock is not null && textBlock.CharacterSpacing > 0)
+				{
+					// Convert back from Em to original value using the extension method
+					return textBlock.CharacterSpacing.FromEm();
+				}
+			}
+
+			return 0.0;
+		}
+
+		[Fact]
+		public async Task CharacterSpacingUpdatesCorrectly()
+		{
+			var datePicker = new DatePickerStub()
+			{
+				Date = DateTime.Today,
+				CharacterSpacing = 5
+			};
+
+			await ValidatePropertyUpdatesValue(
+				datePicker,
+				nameof(IDatePicker.CharacterSpacing),
+				GetNativeCharacterSpacing,
+				5.0,
+				15.0);
+		}
 	}
 }