"Hacky fix" to showcase what the root cause is

Author: nicolaihenriksen

MaterialDesignThemes.Wpf/DialogHost.cs

@@ -369,6 +369,19 @@ private static void IsOpenPropertyChangedCallback(DependencyObject dependencyObj
             var window = Window.GetWindow(dialogHost);
             dialogHost._restoreFocusDialogClose = window != null ? FocusManager.GetFocusedElement(window) : null;
 
+            /* The root cause of the issue is that dialogHost._restoreFocusDialogClose at this point is a TabItem.
+             * So when trying to restore focus when the dialog closes, it will call .Focus() on the TabItem which
+             * effectively does a tab switch if that TabItem is not currently the selected TabItem.
+             *
+             * This IS NOT the right fix, but showcases the issue. How can we go about creating a generic fix for this?
+             * I don't believe TabControl is the only control which is facing this issue. Any control with state similar
+             * to the TabControl would arguably suffer from the same issue.
+             */
+            if (dialogHost._restoreFocusDialogClose is TabItem { Parent: TabControl tabControl })
+            {
+                dialogHost._restoreFocusDialogClose = tabControl;
+            }
+
             //multiple ways of calling back that the dialog has opened:
             // * routed event
             // * the attached property (which should be applied to the button which opened the dialog