AllowNoneSelected hinzugefuegt im SingleSelectSubMenu

MultiTerm.Wpf/Controls/SingleSelectSubMenu.cs

@@ -12,6 +12,10 @@ namespace MultiTerm.Wpf.Controls;
 
 public class SingleSelectSubMenu : MenuItem
 {
+    /// <summary>
+    /// Internal marker for when internal unchecking is ongoing. Unchecking events shall then be ignored.
+    /// </summary>
+    private bool internalUncheckingOngoing = false;
     #region Static Properties
     private static readonly Dictionary<MenuItem, SingleSelectSubMenu> RegisteredSubItemsAndParent = new();
     #endregion
@@ -31,6 +35,11 @@ public class SingleSelectSubMenu : MenuItem
         DependencyProperty.Register("SelectedMenuItem",
         typeof(object), typeof(SingleSelectSubMenu),
         new PropertyMetadata(null, OnSelectedMenuItemPropertyChanged));
+
+    public static readonly DependencyProperty AllowNoneSelectedProperty =
+        DependencyProperty.Register("AllowNoneSelected",
+        typeof(bool), typeof(SingleSelectSubMenu),
+        new PropertyMetadata(false, OnAllowNoneSelectedPropertyChanged));
     #endregion
 
     #region Dotnet Properties
@@ -63,6 +72,16 @@ public class SingleSelectSubMenu : MenuItem
         get { return (string)GetValue(TitleProperty); }
         set { SetValue(TitleProperty, value); }
     }
+
+    /// <summary>
+    /// .NET Property for AllowNoneSelected.
+    /// </summary>
+    [Bindable(false)]
+    public bool AllowNoneSelected
+    {
+        get { return (bool)GetValue(AllowNoneSelectedProperty); }
+        set { SetValue(AllowNoneSelectedProperty, value); }
+    }
     #endregion
 
     /// <summary>
@@ -127,6 +146,7 @@ public class SingleSelectSubMenu : MenuItem
 
             // assign to event handler and register in dictionary
             newMenuItem.Checked += OnAnyItemChecked;
+            newMenuItem.Unchecked += OnAnyItemUnchecked;
             RegisteredSubItemsAndParent.Add(newMenuItem, sssm);
 
             // add to parent (which is expected to be a menu item)
@@ -147,6 +167,10 @@ public class SingleSelectSubMenu : MenuItem
         // get associated menu items
         var associatedMenuitems = GetAssociatedMenuItems(menuItem);
 
+        // get parent sssm 
+        var parentSssm = GetParentSingleSelectSubMenu(menuItem);
+
+        parentSssm.internalUncheckingOngoing = true;
         foreach (var associatedItem in associatedMenuitems)
         {
             // uncheck items that are not null and not the sender item
@@ -155,9 +179,46 @@ public class SingleSelectSubMenu : MenuItem
                 associatedItem.IsChecked = false;
             }
         }
+        parentSssm.internalUncheckingOngoing = false;
 
         // update SelectedMenuItem for respective parent
-        GetParentSingleSelectSubMenu(menuItem).SelectedMenuItem = menuItem;
+        parentSssm.SelectedMenuItem = menuItem;
+    }
+
+    /// <summary>
+    /// Event handler that handles registered menu items being unchecked.
+    /// </summary>
+    /// <param name="sender">MenuItem that was checked</param>
+    /// <param name="e">routed event args</param>
+    private static void OnAnyItemUnchecked(object sender, RoutedEventArgs e)
+    {
+        // extract sender menuItem and guard null
+        if (sender is not MenuItem menuItem) { return; }
+
+        // get parent sssm 
+        var parentSssm = GetParentSingleSelectSubMenu(menuItem);
+        // if automated unchecking is ongoing => ignore events
+        if (parentSssm.internalUncheckingOngoing) { return; }
+
+        // if unselection is not allowed => recheck
+        if (parentSssm.AllowNoneSelected == false)
+        {
+            menuItem.IsChecked = true;
+        }
+    }
+
+    /// <summary>
+    /// Event handler that handles if the property AllowNoneSelected changed.
+    /// </summary>
+    /// <param name="d">sender</param>
+    /// <param name="e">routed event args</param>
+    /// <exception cref="NotImplementedException"></exception>
+    private static void OnAllowNoneSelectedPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
+    {
+        // extract instance and guard null
+        // if (d is not SingleSelectSubMenu sssm) { return; }
+        
+        // nothing to do
     }
 
     #region Helpers