Added automation peer class for expander

Microsoft.Toolkit.Uwp.UI.Controls/Expander/Expander.cs

@@ -5,6 +5,7 @@
 using System;
 using Windows.System;
 using Windows.UI.Xaml;
+using Windows.UI.Xaml.Automation.Peers;
 using Windows.UI.Xaml.Controls;
 using Windows.UI.Xaml.Controls.Primitives;
 using Windows.UI.Xaml.Input;
@@ -76,6 +77,15 @@ protected virtual void OnCollapsed(EventArgs args)
             Collapsed?.Invoke(this, args);
         }
 
+        /// <summary>
+        /// Creates AutomationPeer (<see cref="UIElement.OnCreateAutomationPeer"/>)
+        /// </summary>
+        /// <returns>An automation peer for this <see cref="Expander"/>.</returns>
+        protected override AutomationPeer OnCreateAutomationPeer()
+        {
+            return new ExpanderAutomationPeer(this);
+        }
+
         private void ExpanderToggleButtonPart_KeyDown(object sender, KeyRoutedEventArgs e)
         {
             if (e.Key != VirtualKey.Enter)

Microsoft.Toolkit.Uwp.UI.Controls/Expander/ExpanderAutomationPeer.cs

@@ -0,0 +1,115 @@
+// 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 Windows.UI.Xaml.Automation;
+using Windows.UI.Xaml.Automation.Peers;
+using Windows.UI.Xaml.Automation.Provider;
+
+namespace Microsoft.Toolkit.Uwp.UI.Controls
+{
+    /// <summary>
+    /// Defines a framework element automation peer for the <see cref="Expander"/> control.
+    /// </summary>
+    public class ExpanderAutomationPeer : FrameworkElementAutomationPeer, IToggleProvider
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ExpanderAutomationPeer"/> class.
+        /// </summary>
+        /// <param name="owner">
+        /// The <see cref="Expander" /> that is associated with this <see cref="T:Windows.UI.Xaml.Automation.Peers.ExpanderAutomationPeer" />.
+        /// </param>
+        public ExpanderAutomationPeer(Expander owner)
+            : base(owner)
+        {
+        }
+
+        /// <summary>Gets the toggle state of the control.</summary>
+        /// <returns>The toggle state of the control, as a value of the enumeration.</returns>
+        public ToggleState ToggleState => OwningExpander.IsExpanded ? ToggleState.On : ToggleState.Off;
+
+        private Expander OwningExpander
+        {
+            get
+            {
+                return Owner as Expander;
+            }
+        }
+
+        /// <summary>Cycles through the toggle states of a control.</summary>
+        public void Toggle()
+        {
+            if (!IsEnabled())
+            {
+                throw new ElementNotEnabledException();
+            }
+
+            OwningExpander.IsExpanded = !OwningExpander.IsExpanded;
+        }
+
+        /// <summary>
+        /// Gets the control type for the element that is associated with the UI Automation peer.
+        /// </summary>
+        /// <returns>The control type.</returns>
+        protected override AutomationControlType GetAutomationControlTypeCore()
+        {
+            return AutomationControlType.Custom;
+        }
+
+        /// <summary>
+        /// Called by GetClassName that gets a human readable name that, in addition to AutomationControlType,
+        /// differentiates the control represented by this AutomationPeer.
+        /// </summary>
+        /// <returns>The string that contains the name.</returns>
+        protected override string GetClassNameCore()
+        {
+            return Owner.GetType().Name;
+        }
+
+        /// <summary>
+        /// Called by GetName.
+        /// </summary>
+        /// <returns>
+        /// Returns the first of these that is not null or empty:
+        /// - Value returned by the base implementation
+        /// - Name of the owning Expander
+        /// - Expander class name
+        /// </returns>
+        protected override string GetNameCore()
+        {
+            string name = base.GetNameCore();
+            if (!string.IsNullOrEmpty(name))
+            {
+                return name;
+            }
+
+            if (this.OwningExpander != null)
+            {
+                name = this.OwningExpander.Name;
+            }
+
+            if (string.IsNullOrEmpty(name))
+            {
+                name = this.GetClassName();
+            }
+
+            return name;
+        }
+
+        /// <summary>
+        /// Gets the control pattern that is associated with the specified Windows.UI.Xaml.Automation.Peers.PatternInterface.
+        /// </summary>
+        /// <param name="patternInterface">A value from the Windows.UI.Xaml.Automation.Peers.PatternInterface enumeration.</param>
+        /// <returns>The object that supports the specified pattern, or null if unsupported.</returns>
+        protected override object GetPatternCore(PatternInterface patternInterface)
+        {
+            switch (patternInterface)
+            {
+                case PatternInterface.Toggle:
+                    return this;
+            }
+
+            return base.GetPatternCore(patternInterface);
+        }
+    }
+}