Temporary do not use MemberNotNull

src/Avalonia.Diagnostics/Diagnostics/ViewModels/AvaloniaPropertyViewModel.cs

@@ -1,5 +1,3 @@
-using System.Diagnostics.CodeAnalysis;
-
 namespace Avalonia.Diagnostics.ViewModels
 {
     internal class AvaloniaPropertyViewModel : PropertyViewModel
@@ -10,7 +8,10 @@ namespace Avalonia.Diagnostics.ViewModels
         private string _priority;
         private string _group;
 
+#nullable disable
+        // Remove "nullable disable" after MemberNotNull will work on our CI.
         public AvaloniaPropertyViewModel(AvaloniaObject o, AvaloniaProperty property)
+#nullable restore
         {
             _target = o;
             Property = property;
@@ -47,7 +48,7 @@ namespace Avalonia.Diagnostics.ViewModels
 
         public override string Group => _group;
 
-        [MemberNotNull(nameof(_type), nameof(_group), nameof(_priority))]
+        // [MemberNotNull(nameof(_type), nameof(_group), nameof(_priority))]
         public override void Update()
         {
             if (Property.IsDirect)

src/Avalonia.Diagnostics/Diagnostics/ViewModels/ClrPropertyViewModel.cs

@@ -1,5 +1,4 @@
-using System.Diagnostics.CodeAnalysis;
-using System.Reflection;
+using System.Reflection;
 
 namespace Avalonia.Diagnostics.ViewModels
 {
@@ -9,7 +8,10 @@ namespace Avalonia.Diagnostics.ViewModels
         private string _type;
         private object? _value;
 
+#nullable disable
+        // Remove "nullable disable" after MemberNotNull will work on our CI.
         public ClrPropertyViewModel(object o, PropertyInfo property)
+#nullable restore
         {
             _target = o;
             Property = property;
@@ -47,7 +49,7 @@ namespace Avalonia.Diagnostics.ViewModels
             }
         }
 
-        [MemberNotNull(nameof(_type))]
+        // [MemberNotNull(nameof(_type))]
         public override void Update()
         {
             var val = Property.GetValue(_target);

src/Avalonia.Diagnostics/Diagnostics/ViewModels/MainViewModel.cs

@@ -1,6 +1,5 @@
 using System;
 using System.ComponentModel;
-using System.Diagnostics.CodeAnalysis;
 
 using Avalonia.Controls;
 using Avalonia.Diagnostics.Models;
@@ -24,7 +23,10 @@ namespace Avalonia.Diagnostics.ViewModels
         private bool _shouldVisualizeDirtyRects;
         private bool _showFpsOverlay;
 
+#nullable disable
+        // Remove "nullable disable" after MemberNotNull will work on our CI.
         public MainViewModel(TopLevel root)
+#nullable restore
         {
             _root = root;
             _logicalTree = new TreePageViewModel(this, LogicalTreeNode.Create(root));
@@ -85,7 +87,7 @@ namespace Avalonia.Diagnostics.ViewModels
         public ViewModelBase Content
         {
             get { return _content; }
-            [MemberNotNull(nameof(_content))]
+            // [MemberNotNull(nameof(_content))]
             private set
             {
                 if (_content is TreePageViewModel oldTree &&
@@ -116,7 +118,7 @@ namespace Avalonia.Diagnostics.ViewModels
         public int SelectedTab
         {
             get { return _selectedTab; }
-            [MemberNotNull(nameof(_content))]
+            // [MemberNotNull(nameof(_content))]
             set
             {
                 _selectedTab = value;

src/Avalonia.Diagnostics/Diagnostics/ViewModels/TreeNodeCollection.cs

@@ -3,7 +3,6 @@ using System.Collections;
 using System.Collections.Generic;
 using System.Collections.Specialized;
 using System.ComponentModel;
-using System.Diagnostics.CodeAnalysis;
 
 using Avalonia.Collections;
 
@@ -15,52 +14,22 @@ namespace Avalonia.Diagnostics.ViewModels
 
         public TreeNodeCollection(TreeNode owner) => Owner = owner;
 
-        public TreeNode this[int index]
-        {
-            get
-            {
-                EnsureInitialized();
-                return _inner[index];
-            }
-        }
+        public TreeNode this[int index] => EnsureInitialized()[index];
 
-        public int Count
-        {
-            get
-            {
-                EnsureInitialized();
-                return _inner.Count;
-            }
-        }
+        public int Count => EnsureInitialized().Count;
 
         protected TreeNode Owner { get; }
 
         public event NotifyCollectionChangedEventHandler? CollectionChanged
         {
-            add
-            {
-                EnsureInitialized();
-                _inner.CollectionChanged += value;
-            }
-            remove
-            {
-                EnsureInitialized();
-                _inner.CollectionChanged -= value;
-            }
+            add => EnsureInitialized().CollectionChanged += value;
+            remove => EnsureInitialized().CollectionChanged -= value;
         }
 
         public event PropertyChangedEventHandler? PropertyChanged
         {
-            add
-            {
-                EnsureInitialized();
-                _inner.PropertyChanged += value;
-            }
-            remove
-            {
-                EnsureInitialized();
-                _inner.PropertyChanged -= value;
-            }
+            add => EnsureInitialized().PropertyChanged += value;
+            remove => EnsureInitialized().PropertyChanged -= value;
         }
 
         public virtual void Dispose()
@@ -76,22 +45,21 @@ namespace Avalonia.Diagnostics.ViewModels
 
         public IEnumerator<TreeNode> GetEnumerator()
         {
-            EnsureInitialized();
-            return _inner.GetEnumerator();
+            return EnsureInitialized().GetEnumerator();
         }
 
         IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
 
         protected abstract void Initialize(AvaloniaList<TreeNode> nodes);
 
-        [MemberNotNull(nameof(_inner))]
-        private void EnsureInitialized()
+        private AvaloniaList<TreeNode> EnsureInitialized()
         {
             if (_inner is null)
             {
                 _inner = new AvaloniaList<TreeNode>();
                 Initialize(_inner);
             }
+            return _inner;
         }
     }
 }