[#20] MemberAdminWindow: Add MemberBusinessSharesAdminWindow to manage member shares

Elwig/App.xaml.cs

@@ -344,6 +344,10 @@ namespace Elwig {
             return FocusWindow<DeliveryAdminWindow>(() => new(true), w => w.ViewModel.IsReceipt);
         }
 
+        public static MemberBusinessSharesAdminWindow FocusMemberBusinessSharesWindow(int mgnr) {
+            return FocusWindow<MemberBusinessSharesAdminWindow>(() => new(mgnr), w => w.ViewModel.FilterMember?.MgNr == mgnr);
+        }
+
         public static DeliveryAdminWindow FocusMemberDeliveries(int mgnr) {
             return FocusWindow<DeliveryAdminWindow>(() => new(mgnr), w => w.ViewModel.FilterMember?.MgNr == mgnr);
         }