Fixing trees regression issue

src/Umbraco.Web/FormDataCollectionExtensions.cs

@@ -81,5 +81,24 @@ namespace Umbraco.Web
                 ? converted.Result
                 : default(T);
         }
+
+        /// <summary>
+        /// Returns the object based in the collection based on it's key. This does this with a conversion so if it doesn't convert or the query string is no there an exception is thrown
+        /// </summary>
+        /// <typeparam name="T"></typeparam>
+        /// <param name="items"></param>
+        /// <param name="key"></param>
+        /// <returns></returns>
+        public static T GetRequiredValue<T>(this FormDataCollection items, string key)
+        {
+            var val = items.Get(key);
+            if (string.IsNullOrEmpty(val))
+                throw new InvalidOperationException($"The required query string parameter {key} is missing");
+
+            var converted = val.TryConvertTo<T>();
+            return converted.Success
+                ? converted.Result
+                : throw new InvalidOperationException($"The required query string parameter {key} cannot be converted to type {typeof(T)}");
+        }
     }
 }

src/Umbraco.Web/Trees/ApplicationTreeController.cs

@@ -47,11 +47,11 @@ namespace Umbraco.Web.Trees
         /// </summary>
         /// <param name="application">The application to load tree for</param>
         /// <param name="tree">An optional single tree alias, if specified will only load the single tree for the request app</param>
-        /// <param name="querystring"></param>
+        /// <param name="queryStrings"></param>
         /// <param name="use">Tree use.</param>
         /// <returns></returns>
         [HttpQueryStringFilter("queryStrings")]
-        public async Task<TreeRootNode> GetApplicationTrees(string application, string tree, FormDataCollection querystring, TreeUse use = TreeUse.Main)
+        public async Task<TreeRootNode> GetApplicationTrees(string application, string tree, FormDataCollection queryStrings, TreeUse use = TreeUse.Main)
         {
             application = application.CleanForXss();
 
@@ -75,7 +75,7 @@ namespace Umbraco.Web.Trees
                 if (t == null)
                     throw new HttpResponseException(HttpStatusCode.NotFound);
 
-                var treeRootNode = await GetTreeRootNode(t, Constants.System.Root, querystring);
+                var treeRootNode = await GetTreeRootNode(t, Constants.System.Root, queryStrings);
                 if (treeRootNode != null)
                     return treeRootNode;
 
@@ -89,7 +89,7 @@ namespace Umbraco.Web.Trees
                 var nodes = new TreeNodeCollection();
                 foreach (var t in allTrees)
                 {
-                    var node = await TryGetRootNode(t, querystring);
+                    var node = await TryGetRootNode(t, queryStrings);
                     if (node != null)
                         nodes.Add(node);
                 }
@@ -115,7 +115,7 @@ namespace Umbraco.Web.Trees
                 var nodes = new TreeNodeCollection();
                 foreach (var t in trees)
                 {
-                    var node = await TryGetRootNode(t, querystring);
+                    var node = await TryGetRootNode(t, queryStrings);
                     if (node != null)
                         nodes.Add(node);
                 }

src/Umbraco.Web/Trees/ContentTreeControllerBase.cs

@@ -281,7 +281,7 @@ namespace Umbraco.Web.Trees
                         Services.TextService.Localize("general/recycleBin"),
                         "icon-trash",
                         RecycleBinSmells,
-                        queryStrings.GetValue<string>("application") + TreeAlias.EnsureStartsWith('/') + "/recyclebin"));
+                        queryStrings.GetRequiredValue<string>("application") + TreeAlias.EnsureStartsWith('/') + "/recyclebin"));
 
                 }
 

src/Umbraco.Web/Trees/MemberTreeController.cs

@@ -125,14 +125,14 @@ namespace Umbraco.Web.Trees
             {
                 nodes.Add(
                         CreateTreeNode(Constants.Conventions.MemberTypes.AllMembersListId, id, queryStrings, Services.TextService.Localize("member/allMembers"), "icon-users", true,
-                            queryStrings.GetValue<string>("application") + TreeAlias.EnsureStartsWith('/') + "/list/" + Constants.Conventions.MemberTypes.AllMembersListId));
+                            queryStrings.GetRequiredValue<string>("application") + TreeAlias.EnsureStartsWith('/') + "/list/" + Constants.Conventions.MemberTypes.AllMembersListId));
 
                 if (_isUmbracoProvider)
                 {
                     nodes.AddRange(Services.MemberTypeService.GetAll()
                         .Select(memberType =>
                             CreateTreeNode(memberType.Alias, id, queryStrings, memberType.Name, "icon-users", true,
-                                queryStrings.GetValue<string>("application") + TreeAlias.EnsureStartsWith('/') + "/list/" + memberType.Alias)));
+                                queryStrings.GetRequiredValue<string>("application") + TreeAlias.EnsureStartsWith('/') + "/list/" + memberType.Alias)));
                 }
             }
 

src/Umbraco.Web/Trees/TemplatesTreeController.cs

@@ -75,7 +75,7 @@ namespace Umbraco.Web.Trees
 
             //Create the normal create action
             var item = menu.Items.Add<ActionNew>(Services.TextService, opensDialog: true);
-            item.NavigateToRoute($"{queryStrings.GetValue<string>("application")}/templates/edit/{id}?create=true");
+            item.NavigateToRoute($"{queryStrings.GetRequiredValue<string>("application")}/templates/edit/{id}?create=true");
 
             if (id == Constants.System.Root.ToInvariantString())
             {