[release/11.0.1xx-preview7] Reset WinUI Label line height to default

src/Core/src/Platform/Windows/TextBlockExtensions.cs

@@ -71,6 +71,10 @@ public static void UpdateLineHeight(this TextBlock platformControl, ILabel label
 			{
 				platformControl.LineHeight = label.LineHeight * platformControl.FontSize;
 			}
+			else
+			{
+				platformControl.ClearValue(TextBlock.LineHeightProperty);
+			}
 		}
 
 		public static void UpdateHorizontalTextAlignment(this TextBlock platformControl, ILabel label)

src/Core/tests/DeviceTests/Handlers/Label/LabelHandlerTests.Windows.cs

@@ -3,6 +3,7 @@
 using System.Threading.Tasks;
 using Microsoft.Maui.DeviceTests.Stubs;
 using Microsoft.Maui.Storage;
+using Microsoft.UI.Xaml;
 using Microsoft.UI.Xaml.Controls;
 using Microsoft.UI.Xaml.Media;
 using Xunit;
@@ -81,6 +82,32 @@ public async Task EmbeddedFontFamilyIsCorrectForRendering(bool validateSize)
 			}
 		}
 
+		[Fact(DisplayName = "LineHeight Resets To Default")]
+		public async Task LineHeightResetsToDefault()
+		{
+			var label = new LabelStub
+			{
+				Text = "Test",
+				LineHeight = 3,
+			};
+
+			var handler = await CreateHandlerAsync(label);
+
+			var values = await InvokeOnMainThreadAsync(() =>
+			{
+				var initial = handler.PlatformView.ReadLocalValue(TextBlock.LineHeightProperty);
+
+				label.LineHeight = -1;
+				handler.UpdateValue(nameof(ILabel.LineHeight));
+
+				var reset = handler.PlatformView.ReadLocalValue(TextBlock.LineHeightProperty);
+				return (Initial: initial, Reset: reset);
+			});
+
+			Assert.NotEqual(DependencyProperty.UnsetValue, values.Initial);
+			Assert.Equal(DependencyProperty.UnsetValue, values.Reset);
+		}
+
 		TextBlock GetPlatformLabel(LabelHandler labelHandler) =>
 			labelHandler.PlatformView;