.

Author: SolidProgramming

roles/database/files/sql/idempotent/fworch-texts.sql

@@ -1158,6 +1158,8 @@ INSERT INTO txt VALUES ('edit_interface', 	    'German',	'Schnittstelle bearbeit
 INSERT INTO txt VALUES ('edit_interface', 	    'English',	'Edit Interface');
 INSERT INTO txt VALUES ('interface_contain_nwarea','German', 'Schnittstellen dürfen keine Netzbereiche enthalten');
 INSERT INTO txt VALUES ('interface_contain_nwarea','English','Interfaces must not contain network areas');
+INSERT INTO txt VALUES ('direction_contain_nwarea', 'German','Schnittstelle löschen');
+INSERT INTO txt VALUES ('direction_contain_nwarea', 'English','Delete Interface');
 INSERT INTO txt VALUES ('delete_interface', 	'German',	'Schnittstelle löschen');
 INSERT INTO txt VALUES ('delete_interface', 	'English',	'Delete Interface');
 INSERT INTO txt VALUES ('insert_forbidden', 	'German',	'Einfügen verboten');

roles/lib/files/FWO.Data/Direction.cs

@@ -0,0 +1,8 @@
+namespace FWO.Data
+{
+    public enum Direction
+    {
+        Source,
+        Destination
+    }
+}

roles/lib/files/FWO.Services/ModellingConnectionHandler.cs

@@ -1019,10 +1019,26 @@ public bool CalcVisibility()
             return true;
         }
 
-        public bool NetworkAreaUseAllowed(List<ModellingNetworkArea> networkAreas, out (string Title, string Text) reason)
+        private bool IsAreaForbiddenInDirection(Direction direction)
+        {
+            return direction switch
+            {
+                Direction.Source => ActConn.DestinationAreas.Count > 0,
+                Direction.Destination => ActConn.SourceAreas.Count > 0,
+                _ => false,
+            };
+        }
+
+        /// <summary>
+        /// Checks if the given network areas are allowed in the current connection/interface/service.
+        /// </summary>
+        /// <param name="networkAreas">The list of network areas to check.</param>
+        /// <param name="reason">Out parameter to give context as a reason why it's not allowed, otherwise is's empty.</param>
+        public bool NetworkAreaUseAllowed(List<ModellingNetworkArea> networkAreas, Direction direction, out (string Title, string Text) reason)
         {
             reason.Text = "";
 
+
             if (ActConn.IsCommonService)
             {
                 reason.Title = userConfig.GetText("edit_service");
@@ -1036,6 +1052,12 @@ public bool NetworkAreaUseAllowed(List<ModellingNetworkArea> networkAreas, out (
                 reason.Title = userConfig.GetText("edit_connection");
             }
 
+            if (IsAreaForbiddenInDirection(direction))
+            {
+                reason.Text = userConfig.GetText("direction_contain_nwarea");
+                return false;
+            }
+
             if (ActConn.IsInterface)
             {
                 reason.Text = userConfig.GetText("interface_contain_nwarea");

roles/ui/files/FWO.UI/Pages/NetworkModelling/EditConn.razor

@@ -506,7 +506,7 @@
             }
             if(Container.AreaElements.Count > 0)
             {
-                if (ConnHandler is not null && !ConnHandler.NetworkAreaUseAllowed(Container.AreaElements, out (string Title, string Text) reason))
+                if (ConnHandler is not null && !ConnHandler.NetworkAreaUseAllowed(Container.AreaElements, Direction.Source, out (string Title, string Text) reason))
                 {
                     DisplayMessageInUi(default, reason.Title, reason.Text, true);
                     Container.Clear();
@@ -548,7 +548,7 @@
             }
             if(Container.AreaElements.Count > 0)
             {
-                if (ConnHandler is not null && !ConnHandler.NetworkAreaUseAllowed(Container.AreaElements, out (string Title, string Text) reason))
+                if (ConnHandler is not null && !ConnHandler.NetworkAreaUseAllowed(Container.AreaElements, Direction.Destination, out (string Title, string Text) reason))
                 {
                     DisplayMessageInUi(default, reason.Title, reason.Text, true);
                     Container.Clear();

roles/ui/files/FWO.UI/Pages/NetworkModelling/EditConnLeftSide.razor

@@ -345,7 +345,9 @@
             }
         }
 
-        if (areas.Count > 0 && ConnHandler is not null && !ConnHandler.NetworkAreaUseAllowed(areas, out (string Title, string Text) reason))
+        Direction direction = toSource ? Direction.Source : Direction.Destination;
+
+        if (areas.Count > 0 && ConnHandler is not null && !ConnHandler.NetworkAreaUseAllowed(areas, direction, out (string Title, string Text) reason))
         {
             DisplayMessageInUi(default, reason.Title, reason.Text, true);
             return;