diff --git a/csharp/App/Backend/DataTypes/Methods/Session.cs b/csharp/App/Backend/DataTypes/Methods/Session.cs
index 564f90035..e29e9e769 100644
--- a/csharp/App/Backend/DataTypes/Methods/Session.cs
+++ b/csharp/App/Backend/DataTypes/Methods/Session.cs
@@ -98,15 +98,39 @@ public static class SessionMethods
         var user = session?.User;
 
         var original = Db.GetInstallationById(installation?.Id);
-        
+        var originalOrderNumbers = original!.GetOrderNumbers();
+
+        if (!Equals(originalOrderNumbers, installation?.OrderNumbers))
+        {
+            foreach (var orderNumber in installation!.OrderNumbers)
+            {
+                if (originalOrderNumbers.Contains(orderNumber)) continue;
+                var o2I = new OrderNumber2Installation
+                {
+                    OrderNumber = orderNumber,
+                    InstallationId = installation.Id
+                };
+                Db.Create(o2I);
+            }
+
+            foreach (var orderNumberOld in originalOrderNumbers)
+            {
+                if (!installation!.OrderNumbers.Contains(orderNumberOld))
+                {
+                    Db.OrderNumber2Installation.Delete(i =>
+                        i.InstallationId == installation.Id && i.OrderNumber == orderNumberOld);
+                }
+            }
+        }
+
         return user is not null
-            && installation is not null
-            && original is not null
-            && user.HasWriteAccess
-            && user.HasAccessTo(installation)
-            && installation
-              .WithParentOf(original)  // prevent moving
-              .Apply(Db.Update); 
+               && installation is not null
+               && original is not null
+               && user.HasWriteAccess
+               && user.HasAccessTo(installation)
+               && installation
+                   .WithParentOf(original)  // prevent moving
+                   .Apply(Db.Update); 
     }
 
     public static Boolean Delete(this Session? session, Installation? installation)
diff --git a/csharp/App/Backend/Database/Create.cs b/csharp/App/Backend/Database/Create.cs
index 436ca6246..95849acaa 100644
--- a/csharp/App/Backend/Database/Create.cs
+++ b/csharp/App/Backend/Database/Create.cs
@@ -52,4 +52,9 @@ public static partial class Db
     {
         return Connection.Insert(folderAccess) > 0;
     }
+
+    public static Boolean Create(OrderNumber2Installation o2i)
+    {
+        return Connection.Insert(o2i) > 0;
+    }
 }
\ No newline at end of file
diff --git a/csharp/App/Backend/Database/Db.cs b/csharp/App/Backend/Database/Db.cs
index 161e30485..e9cb827ca 100644
--- a/csharp/App/Backend/Database/Db.cs
+++ b/csharp/App/Backend/Database/Db.cs
@@ -100,4 +100,5 @@ public static partial class Db
               .Select(i => i.RenewS3BucketUrl())
               .WhenAll();
     }
+    
 }
\ No newline at end of file
diff --git a/csharp/App/Backend/Relations/OrderNumber2Installation.cs b/csharp/App/Backend/Relations/OrderNumber2Installation.cs
index ec2b7d84d..a994f7fb7 100644
--- a/csharp/App/Backend/Relations/OrderNumber2Installation.cs
+++ b/csharp/App/Backend/Relations/OrderNumber2Installation.cs
@@ -4,6 +4,7 @@ namespace InnovEnergy.App.Backend.Relations;
 
 public class OrderNumber2Installation : Relation<String, Int64>
 {
-    [Indexed] public String OrderNumber          { get => Left ; init => Left  = value;}
-    [Indexed] public Int64  InstallationId       { get => Right; init => Right = value;}
+    [Indexed] public String OrderNumber          { get => Left ; set => Left  = value;}
+    [Indexed] public Int64  InstallationId       { get => Right; set => Right = value;}
+
 }
\ No newline at end of file
diff --git a/csharp/InnovEnergy.sln.DotSettings b/csharp/InnovEnergy.sln.DotSettings
index 116325457..8232b1720 100644
--- a/csharp/InnovEnergy.sln.DotSettings
+++ b/csharp/InnovEnergy.sln.DotSettings
@@ -34,6 +34,7 @@
 	<s:Boolean x:Key="/Default/UserDictionary/Words/=resultset/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/UserDictionary/Words/=Salimax/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/UserDictionary/Words/=signurl/@EntryIndexedValue">True</s:Boolean>
+	<s:Boolean x:Key="/Default/UserDictionary/Words/=Smpt/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/UserDictionary/Words/=Trumpf/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/UserDictionary/Words/=ttyusb/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/UserDictionary/Words/=tupled/@EntryIndexedValue">True</s:Boolean>