Fixes #3955 - Fixed NRE when setting text on Wide tile only via TileContentBuilder

+ added appropriate unit test to cover this problem for all tile sizes

Author: supermartzin

Microsoft.Toolkit.Uwp.Notifications/Tiles/Builder/TileContentBuilder.cs

@@ -499,7 +499,7 @@ public TileContentBuilder AddAdaptiveTileVisualChild(ITileBindingContentAdaptive
                 GetAdaptiveTileContent(MediumTile).Children.Add(child);
             }
 
-            if (size.HasFlag(TileSize.Wide) && WideTile != null && GetAdaptiveTileContent(MediumTile) != null)
+            if (size.HasFlag(TileSize.Wide) && WideTile != null && GetAdaptiveTileContent(WideTile) != null)
             {
                 GetAdaptiveTileContent(WideTile).Children.Add(child);
             }

UnitTests/UnitTests.Notifications.Shared/TestTileContentBuilder.cs

@@ -0,0 +1,113 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Linq;
+using Microsoft.Toolkit.Uwp.Notifications;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+namespace UnitTests.Notifications
+{
+#if !WINRT
+    [TestClass]
+    public class TestTileContentBuilder
+    {
+        [TestMethod]
+        public void AddTextTest_OnSmallTileOnly()
+        {
+            // Arrange
+            string text = "text on small tile";
+            TileContentBuilder builder = new TileContentBuilder();
+            builder.AddTile(TileSize.Small);
+
+            // Act
+            builder.AddText(text);
+
+            // Assert
+            var tileText = GetTileAdaptiveText(builder, TileSize.Small);
+            Assert.IsNotNull(tileText);
+            Assert.AreSame("text on small tile", (string)tileText.Text);
+        }
+
+        [TestMethod]
+        public void AddTextTest_OnMediumTileOnly()
+        {
+            // Arrange
+            string text = "text on medium tile";
+            TileContentBuilder builder = new TileContentBuilder();
+            builder.AddTile(TileSize.Medium);
+
+            // Act
+            builder.AddText(text);
+
+            // Assert
+            var tileText = GetTileAdaptiveText(builder, TileSize.Medium);
+            Assert.IsNotNull(tileText);
+            Assert.AreSame("text on medium tile", (string)tileText.Text);
+        }
+
+        [TestMethod]
+        public void AddTextTest_OnWideTileOnly()
+        {
+            // Arrange
+            string text = "text on wide tile";
+            TileContentBuilder builder = new TileContentBuilder();
+            builder.AddTile(TileSize.Wide);
+
+            // Act
+            builder.AddText(text);
+
+            // Assert
+            var tileText = GetTileAdaptiveText(builder, TileSize.Wide);
+            Assert.IsNotNull(tileText);
+            Assert.AreSame("text on wide tile", (string)tileText.Text);
+        }
+
+        [TestMethod]
+        public void AddTextTest_OnLargeTileOnly()
+        {
+            // Arrange
+            string text = "text on large tile";
+            TileContentBuilder builder = new TileContentBuilder();
+            builder.AddTile(TileSize.Large);
+
+            // Act
+            builder.AddText(text);
+
+            // Assert
+            var tileText = GetTileAdaptiveText(builder, TileSize.Large);
+            Assert.IsNotNull(tileText);
+            Assert.AreSame("text on large tile", (string)tileText.Text);
+        }
+
+        private static AdaptiveText GetTileAdaptiveText(TileContentBuilder builder, TileSize size)
+        {
+            TileBinding tileBinding;
+            switch (size)
+            {
+                case TileSize.Small:
+                    tileBinding = builder.Content.Visual.TileSmall;
+                    break;
+
+                case TileSize.Medium:
+                    tileBinding = builder.Content.Visual.TileMedium;
+                    break;
+
+                case TileSize.Wide:
+                    tileBinding = builder.Content.Visual.TileWide;
+                    break;
+
+                case TileSize.Large:
+                    tileBinding = builder.Content.Visual.TileLarge;
+                    break;
+
+                default:
+                    return null;
+            }
+
+            var content = (TileBindingContentAdaptive)tileBinding.Content;
+            return content.Children.FirstOrDefault() as AdaptiveText;
+        }
+    }
+#endif
+}

UnitTests/UnitTests.Notifications.Shared/UnitTests.Notifications.Shared.projitems

@@ -11,6 +11,7 @@
   <ItemGroup>
     <Compile Include="$(MSBuildThisFileDirectory)TestAssertHelper.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)TestMail.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)TestTileContentBuilder.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)TestToastArguments.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)TestToastContentBuilder.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)TestWeather.cs" />