Update some C# examples for 4.0 (#6693)

* Update some C# examples

- Rename members that have been renamed in Godot's C# API for 4.0.
- Change `delta` parameter type to `double`.
- Ensure parameters match base declaration.
- Other minor code fixes.

---------

Co-authored-by: Paul Joannon <437025+paulloz@users.noreply.github.com>

tutorials/best_practices/data_preferences.rst

@@ -249,28 +249,25 @@ tree structures.
   .. code-tab:: csharp
 
     using Godot;
+    using System.Collections.Generic;
 
     // Can decide whether to expose getters/setters for properties later
-    public partial class TreeNode : Object
+    public partial class TreeNode : GodotObject
     {
         private TreeNode _parent = null;
 
-        private object[] _children = new object[0];
+        private List<TreeNode> _children = new();
 
-        public override void Notification(int what)
+        public override void _Notification(int what)
         {
             switch (what)
             {
                 case NotificationPredelete:
-                    foreach (object child in _children)
+                    foreach (TreeNode child in _children)
                     {
-                        TreeNode node = child as TreeNode;
-                        if (node != null)
-                            node.Free();
+                        node.Free();
                     }
                     break;
-                default:
-                    break;
             }
         }
     }

tutorials/best_practices/godot_interfaces.rst

@@ -26,8 +26,8 @@ is to get a reference to an existing object from another acquired instance.
 
   .. code-tab:: csharp
 
-    Object obj = node.Object; // Property access.
-    Object obj = node.GetObject(); // Method access.
+    GodotObject obj = node.Object; // Property access.
+    GodotObject obj = node.GetObject(); // Method access.
 
 The same principle applies for :ref:`RefCounted <class_RefCounted>` objects.
 While users often access :ref:`Node <class_Node>` and
@@ -181,31 +181,35 @@ Nodes likewise have an alternative access point: the SceneTree.
 
   .. code-tab:: csharp
 
-    public class MyNode
+    using Godot;
+    using System;
+    using System.Diagnostics;
+
+    public class MyNode : Node
     {
         // Slow
         public void DynamicLookupWithDynamicNodePath()
         {
-            GD.Print(GetNode(NodePath("Child")));
+            GD.Print(GetNode("Child"));
         }
 
         // Fastest. Lookup node and cache for future access.
         // Doesn't break if node moves later.
-        public Node Child;
+        private Node _child;
         public void _Ready()
         {
-            Child = GetNode(NodePath("Child"));
+            _child = GetNode("Child");
         }
         public void LookupAndCacheForFutureAccess()
         {
-            GD.Print(Child);
+            GD.Print(_child);
         }
 
         // Delegate reference assignment to an external source.
         // Con: need to perform a validation check.
         // Pro: node makes no requirements of its external structure.
         //      'prop' can come from anywhere.
-        public object Prop;
+        public object Prop { get; set; }
         public void CallMeAfterPropIsInitializedByParent()
         {
             // Validate prop in one of three ways.
@@ -223,7 +227,15 @@ Nodes likewise have an alternative access point: the SceneTree.
                 return;
             }
 
+            // Fail with an exception.
+            if (prop == null)
+            {
+                throw new InvalidOperationException("'Prop' wasn't initialized.");
+            }
+
             // Fail and terminate.
+            // Note: Scripts run from a release export template don't
+            // run `Debug.Assert` statements.
             Debug.Assert(Prop, "'Prop' wasn't initialized");
         }
 
@@ -232,10 +244,10 @@ Nodes likewise have an alternative access point: the SceneTree.
         // that manage their own data and don't interfere with other objects.
         public void ReferenceAGlobalAutoloadedVariable()
         {
-            Node globals = GetNode(NodePath("/root/Globals"));
+            MyNode globals = GetNode<MyNode>("/root/Globals");
             GD.Print(globals);
-            GD.Print(globals.prop);
-            GD.Print(globals.my_getter());
+            GD.Print(globals.Prop);
+            GD.Print(globals.MyGetter());
         }
     };
 

tutorials/best_practices/godot_notifications.rst

@@ -119,7 +119,7 @@ deltatime methods as needed.
     {
 
         // Called every frame, even when the engine detects no input.
-        public void _Process(float delta)
+        public void _Process(double delta)
         {
             if (Input.IsActionJustPressed("ui_select"))
                 GD.Print(delta);
@@ -130,12 +130,10 @@ deltatime methods as needed.
         {
             switch (event)
             {
-                case InputEventKey keyEvent:
+                case InputEventKey:
                     if (Input.IsActionJustPressed("ui_accept"))
                         GD.Print(GetProcessDeltaTime());
                     break;
-                default:
-                    break;
             }
         }
 
@@ -187,7 +185,7 @@ instantiation:
             set
             {
                 _test = value;
-                GD.Print("Setting: " + _test);
+                GD.Print($"Setting: {_test}");
             }
         }