Properly add and remove reflect children

src/System.Windows.Forms/src/System/Windows/Forms/Control.cs

@@ -3271,11 +3271,9 @@ private Control ReflectParent
                     value.AddReflectChild();
                 }
 
+                Control existing = _reflectParent as Control;
                 _reflectParent = value;
-                if (ReflectParent is Control c)
-                {
-                    c.RemoveReflectChild();
-                }
+                existing?.RemoveReflectChild();
             }
         }
 

src/System.Windows.Forms/tests/IntegrationTests/System.Windows.Forms.IntegrationTests.Common/MainFormControlsTabOrder.cs

@@ -22,6 +22,8 @@ public enum MainFormControlsTabOrder
         MdiParent,
         PropertyGrid,
         ListView,
-        FontNameEditor
+        FontNameEditor,
+        CollectionEditors,
+        RichTextBoxes
     }
 }

src/System.Windows.Forms/tests/IntegrationTests/System.Windows.Forms.IntegrationTests/WinformsControlsTest.cs

@@ -65,10 +65,10 @@ public void WinformsControlsTest_CalendarTest()
         }
 
         [Fact]
-        public void WinformsControlsTest_TreeViewAndImageListTest()
+        public void WinformsControlsTest_MultipleControlsTest()
         {
-            var process = TestHelpers.StartProcess(_exePath);
-            TestHelpers.PressTabsOnProcess(process, 2);
+            Process process = TestHelpers.StartProcess(_exePath);
+            TestHelpers.PressTabsOnProcess(process, MainFormControlsTabOrder.MultipleControls);
             TestHelpers.PressEnterOnProcess(process);
 
             Assert.False(process.HasExited);
@@ -80,10 +80,10 @@ public void WinformsControlsTest_TreeViewAndImageListTest()
         }
 
         [Fact]
-        public void WinformsControlsTest_ContentAlignmentTest()
+        public void WinformsControlsTest_ComboBoxesTest()
         {
             Process process = TestHelpers.StartProcess(_exePath);
-            TestHelpers.PressTabsOnProcess(process, MainFormControlsTabOrder.ContentAlignment);
+            TestHelpers.PressTabsOnProcess(process, MainFormControlsTabOrder.ComboBoxes);
             TestHelpers.PressEnterOnProcess(process);
 
             Assert.False(process.HasExited);
@@ -95,10 +95,10 @@ public void WinformsControlsTest_ContentAlignmentTest()
         }
 
         [Fact]
-        public void WinformsControlsTest_MultipleControlsTest()
+        public void WinformsControlsTest_DateTimePickerTest()
         {
             Process process = TestHelpers.StartProcess(_exePath);
-            TestHelpers.PressTabsOnProcess(process, MainFormControlsTabOrder.MultipleControls);
+            TestHelpers.PressTabsOnProcess(process, MainFormControlsTabOrder.DateTimePickerButton);
             TestHelpers.PressEnterOnProcess(process);
 
             Assert.False(process.HasExited);
@@ -109,11 +109,16 @@ public void WinformsControlsTest_MultipleControlsTest()
             Assert.True(process.HasExited);
         }
 
+        // FolderBrower
+
         [Fact]
-        public void WinformsControlsTest_DataGridViewTest()
+        public void WinformsControlsTest_ThreadExceptionDialogTest()
         {
             Process process = TestHelpers.StartProcess(_exePath);
-            TestHelpers.PressTabsOnProcess(process, MainFormControlsTabOrder.DataGridView);
+            TestHelpers.PressTabsOnProcess(process, MainFormControlsTabOrder.ThreadExceptionDialog);
+            TestHelpers.PressEnterOnProcess(process);
+
+            TestHelpers.PressTabsOnProcess(process, 2);
             TestHelpers.PressEnterOnProcess(process);
 
             Assert.False(process.HasExited);
@@ -125,10 +130,10 @@ public void WinformsControlsTest_DataGridViewTest()
         }
 
         [Fact]
-        public void WinformsControlsTest_MenusTest()
+        public void WinformsControlsTest_DataGridViewTest()
         {
             Process process = TestHelpers.StartProcess(_exePath);
-            TestHelpers.PressTabsOnProcess(process, MainFormControlsTabOrder.Menus);
+            TestHelpers.PressTabsOnProcess(process, MainFormControlsTabOrder.DataGridView);
             TestHelpers.PressEnterOnProcess(process);
 
             Assert.False(process.HasExited);
@@ -140,10 +145,10 @@ public void WinformsControlsTest_MenusTest()
         }
 
         [Fact]
-        public void WinformsControlsTest_PanelsTest()
+        public void WinformsControlsTest_TreeViewAndImageListTest()
         {
-            Process process = TestHelpers.StartProcess(_exePath);
-            TestHelpers.PressTabsOnProcess(process, MainFormControlsTabOrder.Panels);
+            var process = TestHelpers.StartProcess(_exePath);
+            TestHelpers.PressTabsOnProcess(process, 2);
             TestHelpers.PressEnterOnProcess(process);
 
             Assert.False(process.HasExited);
@@ -155,10 +160,10 @@ public void WinformsControlsTest_PanelsTest()
         }
 
         [Fact]
-        public void WinformsControlsTest_SplitterTest()
+        public void WinformsControlsTest_ContentAlignmentTest()
         {
             Process process = TestHelpers.StartProcess(_exePath);
-            TestHelpers.PressTabsOnProcess(process, MainFormControlsTabOrder.Splitter);
+            TestHelpers.PressTabsOnProcess(process, MainFormControlsTabOrder.ContentAlignment);
             TestHelpers.PressEnterOnProcess(process);
 
             Assert.False(process.HasExited);
@@ -170,10 +175,10 @@ public void WinformsControlsTest_SplitterTest()
         }
 
         [Fact]
-        public void WinformsControlsTest_ComboBoxesTest()
+        public void WinformsControlsTest_MenusTest()
         {
             Process process = TestHelpers.StartProcess(_exePath);
-            TestHelpers.PressTabsOnProcess(process, MainFormControlsTabOrder.ComboBoxes);
+            TestHelpers.PressTabsOnProcess(process, MainFormControlsTabOrder.Menus);
             TestHelpers.PressEnterOnProcess(process);
 
             Assert.False(process.HasExited);
@@ -185,10 +190,10 @@ public void WinformsControlsTest_ComboBoxesTest()
         }
 
         [Fact]
-        public void WinformsControlsTest_MDIParentTest()
+        public void WinformsControlsTest_PanelsTest()
         {
             Process process = TestHelpers.StartProcess(_exePath);
-            TestHelpers.PressTabsOnProcess(process, MainFormControlsTabOrder.MdiParent);
+            TestHelpers.PressTabsOnProcess(process, MainFormControlsTabOrder.Panels);
             TestHelpers.PressEnterOnProcess(process);
 
             Assert.False(process.HasExited);
@@ -200,10 +205,10 @@ public void WinformsControlsTest_MDIParentTest()
         }
 
         [Fact]
-        public void WinformsControlsTest_PropertyGridTest()
+        public void WinformsControlsTest_SplitterTest()
         {
             Process process = TestHelpers.StartProcess(_exePath);
-            TestHelpers.PressTabsOnProcess(process, MainFormControlsTabOrder.PropertyGrid);
+            TestHelpers.PressTabsOnProcess(process, MainFormControlsTabOrder.Splitter);
             TestHelpers.PressEnterOnProcess(process);
 
             Assert.False(process.HasExited);
@@ -215,10 +220,10 @@ public void WinformsControlsTest_PropertyGridTest()
         }
 
         [Fact]
-        public void WinformsControlsTest_FontNameEditorTest()
+        public void WinformsControlsTest_MDIParentTest()
         {
             Process process = TestHelpers.StartProcess(_exePath);
-            TestHelpers.PressTabsOnProcess(process, MainFormControlsTabOrder.FontNameEditor);
+            TestHelpers.PressTabsOnProcess(process, MainFormControlsTabOrder.MdiParent);
             TestHelpers.PressEnterOnProcess(process);
 
             Assert.False(process.HasExited);
@@ -230,18 +235,12 @@ public void WinformsControlsTest_FontNameEditorTest()
         }
 
         [Fact]
-        public void WinformsControlsTest_PropertyGrid_CollectionEditorTest()
+        public void WinformsControlsTest_PropertyGridTest()
         {
             Process process = TestHelpers.StartProcess(_exePath);
             TestHelpers.PressTabsOnProcess(process, MainFormControlsTabOrder.PropertyGrid);
             TestHelpers.PressEnterOnProcess(process);
 
-            TestHelpers.PressTabOnProcess(process);
-            TestHelpers.PressRightOnProcess(process); // once
-            TestHelpers.PressRightOnProcess(process); // twice
-            TestHelpers.PressTabsOnProcess(process, 2);
-            TestHelpers.PressEnterOnProcess(process);
-
             Assert.False(process.HasExited);
 
             process.Kill();
@@ -267,10 +266,10 @@ public void WinformsControlsTest_PropertyGrid_CollectionEditorTest()
         // }
 
         [Fact]
-        public void WinformsControlsTest_DateTimePickerTest()
+        public void WinformsControlsTest_FontNameEditorTest()
         {
             Process process = TestHelpers.StartProcess(_exePath);
-            TestHelpers.PressTabsOnProcess(process, MainFormControlsTabOrder.DateTimePickerButton);
+            TestHelpers.PressTabsOnProcess(process, MainFormControlsTabOrder.FontNameEditor);
             TestHelpers.PressEnterOnProcess(process);
 
             Assert.False(process.HasExited);
@@ -282,12 +281,15 @@ public void WinformsControlsTest_DateTimePickerTest()
         }
 
         [Fact]
-        public void WinformsControlsTest_ThreadExceptionDialogTest()
+        public void WinformsControlsTest_PropertyGrid_CollectionEditorTest()
         {
             Process process = TestHelpers.StartProcess(_exePath);
-            TestHelpers.PressTabsOnProcess(process, MainFormControlsTabOrder.ThreadExceptionDialog);
+            TestHelpers.PressTabsOnProcess(process, MainFormControlsTabOrder.PropertyGrid);
             TestHelpers.PressEnterOnProcess(process);
 
+            TestHelpers.PressTabOnProcess(process);
+            TestHelpers.PressRightOnProcess(process); // once
+            TestHelpers.PressRightOnProcess(process); // twice
             TestHelpers.PressTabsOnProcess(process, 2);
             TestHelpers.PressEnterOnProcess(process);
 
@@ -298,5 +300,20 @@ public void WinformsControlsTest_ThreadExceptionDialogTest()
 
             Assert.True(process.HasExited);
         }
+
+        [Fact]
+        public void WinformsControlsTest_RichTextBoxesTest()
+        {
+            Process process = TestHelpers.StartProcess(_exePath);
+            TestHelpers.PressTabsOnProcess(process, MainFormControlsTabOrder.RichTextBoxes);
+            TestHelpers.PressEnterOnProcess(process);
+
+            Assert.False(process.HasExited);
+
+            process.Kill();
+            process.WaitForExit();
+
+            Assert.True(process.HasExited);
+        }
     }
 }

src/System.Windows.Forms/tests/IntegrationTests/WinFormsControlsClassicTests/WinFormsControlsClassicTests.csproj

@@ -209,6 +209,14 @@
       <Link>PropertyGrid.Designer.cs</Link>
       <DependentUpon>PropertyGrid.cs</DependentUpon>
     </Compile>
+    <Compile Include="..\WinformsControlsTest\RichTextBoxes.cs">
+      <Link>RichTextBoxes.cs</Link>
+      <SubType>Form</SubType>
+    </Compile>
+    <Compile Include="..\WinformsControlsTest\RichTextBoxes.Designer.cs">
+      <Link>RichTextBoxes.Designer.cs</Link>
+      <DependentUpon>RichTextBoxes.cs</DependentUpon>
+    </Compile>
     <Compile Include="..\WinformsControlsTest\ScalingBeforeChanges.cs">
       <Link>ScalingBeforeChanges.cs</Link>
       <SubType>Form</SubType>
@@ -272,6 +280,10 @@
       <Link>ListViewTest.resx</Link>
       <DependentUpon>ListViewTest.cs</DependentUpon>
     </EmbeddedResource>
+    <EmbeddedResource Include="..\WinformsControlsTest\MainForm.resx">
+      <Link>MainForm.resx</Link>
+      <DependentUpon>MainForm.cs</DependentUpon>
+    </EmbeddedResource>
     <EmbeddedResource Include="..\WinformsControlsTest\MdiChild.resx">
       <Link>MdiChild.resx</Link>
       <DependentUpon>MdiChild.cs</DependentUpon>
@@ -310,6 +322,10 @@
     </EmbeddedResource>
   </ItemGroup>
   <ItemGroup>
+    <None Include="..\WinformsControlsTest\Data\example.rtf">
+      <Link>Data\example.rtf</Link>
+      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
+    </None>
     <None Include="App.config" />
   </ItemGroup>
   <ItemGroup>

src/System.Windows.Forms/tests/IntegrationTests/WinformsControlsTest/ComboBoxes.cs

@@ -17,6 +17,12 @@ public partial class ComboBoxes : Form
         public ComboBoxes()
         {
             InitializeComponent();
+            comboBox1.SelectedIndex = 0;
+        }
+
+        private void ComboBox1_SelectedIndexChanged(object sender, EventArgs e)
+        {
+            label1.Text = comboBox1.Text;
         }
     }
 }