V8: Duplicate MemberGroup names cause MemberGroup mixup

src/Umbraco.Web.UI/Umbraco/config/lang/en.xml

@@ -1477,6 +1477,7 @@ To manage your website, simply open the Umbraco backoffice and start adding cont
     <key alias="mediaTypeSavedHeader">Media Type saved</key>
     <key alias="memberTypeSavedHeader">Member Type saved</key>
     <key alias="memberGroupSavedHeader">Member Group saved</key>
+    <key alias="memberGroupNameDuplicate">Another Member Group with the same name already exists</key>
     <key alias="templateErrorHeader">Template not saved</key>
     <key alias="templateErrorText">Please make sure that you do not have 2 templates with the same alias</key>
     <key alias="templateSavedHeader">Template saved</key>

src/Umbraco.Web.UI/Umbraco/config/lang/en_us.xml

@@ -1488,6 +1488,7 @@ To manage your website, simply open the Umbraco backoffice and start adding cont
     <key alias="mediaTypeSavedHeader">Media Type saved</key>
     <key alias="memberTypeSavedHeader">Member Type saved</key>
     <key alias="memberGroupSavedHeader">Member Group saved</key>
+    <key alias="memberGroupNameDuplicate">Another Member Group with the same name already exists</key>
     <key alias="templateErrorHeader">Template not saved</key>
     <key alias="templateErrorText">Please make sure that you do not have 2 templates with the same alias</key>
     <key alias="templateSavedHeader">Template saved</key>

src/Umbraco.Web.UI/Umbraco/config/lang/fr.xml

@@ -1411,6 +1411,7 @@ Pour gérer votre site, ouvrez simplement le backoffice Umbraco et commencez à
     <key alias="mediaTypeSavedHeader">Type de média sauvegardé</key>
     <key alias="memberTypeSavedHeader">Type de membre sauvegardé</key>
     <key alias="memberGroupSavedHeader">Groupe de membres sauvegardé</key>
+    <key alias="memberGroupNameDuplicate">Un autre groupe de membres existe déjà avec le même nom</key>
     <key alias="templateErrorHeader">Modèle non sauvegardé</key>
     <key alias="templateErrorText">Assurez-vous de ne pas avoir 2 modèles avec le même alias.</key>
     <key alias="templateSavedHeader">Modèle sauvegardé</key>

src/Umbraco.Web.UI/Umbraco/config/lang/nl.xml

@@ -1276,6 +1276,7 @@ Echter, Runway biedt een gemakkelijke basis om je snel op weg te helpen. Als je
     <key alias="mediaTypeSavedHeader">Mediatype opgeslagen</key>
     <key alias="memberTypeSavedHeader">Ledentype opgeslagen</key>
     <key alias="memberGroupSavedHeader">Ledengroep opgeslagen</key>
+    <key alias="memberGroupNameDuplicate">Er bestaat al een andere ledengroep met dezelfde naam</key>
     <key alias="templateErrorHeader">Sjabloon niet opgeslagen</key>
     <key alias="templateErrorText">Controleer dat je geen 2 sjablonen met dezelfde naam hebt</key>
     <key alias="templateSavedHeader">Sjabloon opgeslagen</key>

src/Umbraco.Web/Editors/MemberGroupController.cs

@@ -135,6 +135,19 @@ public MemberGroupDisplay GetEmpty()
             return Mapper.Map<IMemberGroup, MemberGroupDisplay>(item);
         }
 
+        public bool IsMemberGroupNameUnique(int id, string oldName, string newName)
+        {
+            if (newName == oldName)
+                return true; // name hasn't changed
+
+            var service = Services.MemberGroupService;
+            var memberGroup = service.GetByName(newName);
+            if (memberGroup == null)
+                return true; // no member group found
+
+            return memberGroup.Id == id;
+        }
+
         public MemberGroupDisplay PostSave(MemberGroupSave saveModel)
         {
             var service = Services.MemberGroupService;
@@ -146,16 +159,27 @@ public MemberGroupDisplay PostSave(MemberGroupSave saveModel)
                 throw new HttpResponseException(HttpStatusCode.NotFound);
             }
 
-            memberGroup.Name = saveModel.Name;
-            service.Save(memberGroup);
+            if (IsMemberGroupNameUnique(memberGroup.Id, memberGroup.Name, saveModel.Name))
+            {
+                memberGroup.Name = saveModel.Name;
+                service.Save(memberGroup);
 
-            var display = Mapper.Map<IMemberGroup, MemberGroupDisplay>(memberGroup);
+                var display = Mapper.Map<IMemberGroup, MemberGroupDisplay>(memberGroup);
+                display.AddSuccessNotification(
+                                Services.TextService.Localize("speechBubbles", "memberGroupSavedHeader"),
+                                string.Empty);
 
-            display.AddSuccessNotification(
-                            Services.TextService.Localize("speechBubbles", "memberGroupSavedHeader"),
-                            string.Empty);
+                return display;
+            }
+            else
+            {
+                var display = Mapper.Map<IMemberGroup, MemberGroupDisplay>(memberGroup);
+                display.AddErrorNotification(
+                                Services.TextService.Localize("speechBubbles", "memberGroupNameDuplicate"),
+                                string.Empty);
 
-            return display;
+                return display;
+            }            
         }
     }
 }