public static void ReadOnlyProperties()
        {
            ControllerTools.ResetExpectedName();

            Main RootNode;
            IReadOnlyRootNodeIndex RootIndex0;
            IReadOnlyRootNodeIndex RootIndex1;

            RootNode = CreateRoot(ValueGuid0, Imperfections.None);
            Assert.That(BaseNodeHelper.NodeTreeDiagnostic.IsValid(RootNode));

            RootIndex0 = new ReadOnlyRootNodeIndex(RootNode);
            Assert.That(RootIndex0.Node == RootNode);
            Assert.That(RootIndex0.IsEqual(CompareEqual.New(), RootIndex0));

            RootIndex1 = new ReadOnlyRootNodeIndex(RootNode);
            Assert.That(RootIndex1.Node == RootNode);
            Assert.That(CompareEqual.CoverIsEqual(RootIndex0, RootIndex1));

            ReadOnlyController Controller0 = ReadOnlyController.Create(RootIndex0);

            Assert.That(Controller0.RootIndex == RootIndex0);

            Stats Stats = Controller0.Stats;

            Assert.That(Stats.NodeCount >= 0);
            Assert.That(Stats.PlaceholderNodeCount >= 0);
            Assert.That(Stats.OptionalNodeCount >= 0);
            Assert.That(Stats.AssignedOptionalNodeCount >= 0);
            Assert.That(Stats.ListCount >= 0);
            Assert.That(Stats.BlockListCount >= 0);
            Assert.That(Stats.BlockCount >= 0);

            IReadOnlyPlaceholderNodeState RootState = Controller0.RootState;

            Assert.That(RootState.ParentIndex == RootIndex0);

            Assert.That(Controller0.Contains(RootIndex0));
            Assert.That(Controller0.IndexToState(RootIndex0) == RootState);

            Assert.That(RootState.InnerTable.Count == 8);
            Assert.That(RootState.InnerTable.ContainsKey(nameof(Main.PlaceholderTree)));
            Assert.That(RootState.InnerTable.ContainsKey(nameof(Main.PlaceholderLeaf)));
            Assert.That(RootState.InnerTable.ContainsKey(nameof(Main.UnassignedOptionalLeaf)));
            Assert.That(RootState.InnerTable.ContainsKey(nameof(Main.EmptyOptionalLeaf)));
            Assert.That(RootState.InnerTable.ContainsKey(nameof(Main.AssignedOptionalTree)));
            Assert.That(RootState.InnerTable.ContainsKey(nameof(Main.AssignedOptionalLeaf)));
            Assert.That(RootState.InnerTable.ContainsKey(nameof(Main.LeafBlocks)));
            Assert.That(RootState.InnerTable.ContainsKey(nameof(Main.LeafPath)));

            IReadOnlyPlaceholderInner MainPlaceholderTreeInner = (IReadOnlyPlaceholderInner)RootState.PropertyToInner(nameof(Main.PlaceholderTree));

            Assert.That(MainPlaceholderTreeInner != null);
            if (MainPlaceholderTreeInner != null)
            {
                Assert.That(MainPlaceholderTreeInner.InterfaceType.IsTypeof <Tree>());
                Assert.That(MainPlaceholderTreeInner.ChildState != null);
                Assert.That(MainPlaceholderTreeInner.ChildState?.ParentInner == MainPlaceholderTreeInner);
            }

            IReadOnlyPlaceholderInner MainPlaceholderLeafInner = (IReadOnlyPlaceholderInner)RootState.PropertyToInner(nameof(Main.PlaceholderLeaf));

            Assert.That(MainPlaceholderLeafInner != null);
            if (MainPlaceholderLeafInner != null)
            {
                Assert.That(MainPlaceholderLeafInner.InterfaceType.IsTypeof <Leaf>());
                Assert.That(MainPlaceholderLeafInner.ChildState != null);
                Assert.That(MainPlaceholderLeafInner.ChildState?.ParentInner == MainPlaceholderLeafInner);
            }

            IReadOnlyOptionalInner MainUnassignedOptionalInner = (IReadOnlyOptionalInner)RootState.PropertyToInner(nameof(Main.UnassignedOptionalLeaf));

            Assert.That(MainUnassignedOptionalInner != null);
            if (MainUnassignedOptionalInner != null)
            {
                Assert.That(MainUnassignedOptionalInner.InterfaceType.IsTypeof <Leaf>());
                Assert.That(!MainUnassignedOptionalInner.IsAssigned);
                Assert.That(MainUnassignedOptionalInner.ChildState != null);
                Assert.That(MainUnassignedOptionalInner.ChildState?.ParentInner == MainUnassignedOptionalInner);
            }

            IReadOnlyOptionalInner MainAssignedOptionalTreeInner = (IReadOnlyOptionalInner)RootState.PropertyToInner(nameof(Main.AssignedOptionalTree));

            Assert.That(MainAssignedOptionalTreeInner != null);
            if (MainAssignedOptionalTreeInner != null)
            {
                Assert.That(MainAssignedOptionalTreeInner.InterfaceType.IsTypeof <Tree>());
                Assert.That(MainAssignedOptionalTreeInner.IsAssigned);
            }

            IReadOnlyNodeState AssignedOptionalTreeState = MainAssignedOptionalTreeInner.ChildState;

            Assert.That(AssignedOptionalTreeState != null);
            if (AssignedOptionalTreeState != null)
            {
                Assert.That(AssignedOptionalTreeState.ParentInner == MainAssignedOptionalTreeInner);
                Assert.That(AssignedOptionalTreeState.ParentState == RootState);
            }

            ReadOnlyNodeStateReadOnlyList AssignedOptionalTreeAllChildren = AssignedOptionalTreeState.GetAllChildren();

            Assert.That(AssignedOptionalTreeAllChildren.Count == 2, $"New count: {AssignedOptionalTreeAllChildren.Count}");

            IReadOnlyOptionalInner MainAssignedOptionalLeafInner = (IReadOnlyOptionalInner)RootState.PropertyToInner(nameof(Main.AssignedOptionalLeaf));

            Assert.That(MainAssignedOptionalLeafInner != null);
            if (MainAssignedOptionalLeafInner != null)
            {
                Assert.That(MainAssignedOptionalLeafInner.InterfaceType.IsTypeof <Leaf>());
                Assert.That(MainAssignedOptionalLeafInner.IsAssigned);
                Assert.That(MainAssignedOptionalLeafInner.ChildState != null);
                Assert.That(MainAssignedOptionalLeafInner.ChildState.ParentInner == MainAssignedOptionalLeafInner);
            }

            IReadOnlyBlockListInner MainLeafBlocksInner = (IReadOnlyBlockListInner)RootState.PropertyToInner(nameof(Main.LeafBlocks));

            Assert.That(MainLeafBlocksInner != null);
            if (MainLeafBlocksInner != null)
            {
                Assert.That(!MainLeafBlocksInner.IsNeverEmpty);
                Assert.That(!MainLeafBlocksInner.IsEmpty);
                Assert.That(!MainLeafBlocksInner.IsSingle);
                Assert.That(MainLeafBlocksInner.InterfaceType.IsTypeof <Leaf>());
                Assert.That(MainLeafBlocksInner.BlockType.IsTypeof <BaseNode.IBlock <Leaf> >());
                Assert.That(MainLeafBlocksInner.ItemType.IsTypeof <Leaf>());
                Assert.That(MainLeafBlocksInner.Count == 4);
                Assert.That(MainLeafBlocksInner.BlockStateList != null);
                Assert.That(MainLeafBlocksInner.BlockStateList.Count == 3);
                Assert.That(MainLeafBlocksInner.AllIndexes().Count == MainLeafBlocksInner.Count);
            }

            IReadOnlyBlockState LeafBlock = MainLeafBlocksInner.BlockStateList[0];

            Assert.That(LeafBlock != null);
            if (LeafBlock != null)
            {
                Assert.That(LeafBlock.StateList != null);
                Assert.That(LeafBlock.StateList.Count == 1);
                Assert.That(MainLeafBlocksInner.FirstNodeState == LeafBlock.StateList[0]);
                Assert.That(MainLeafBlocksInner.IndexAt(0, 0) == MainLeafBlocksInner.FirstNodeState.ParentIndex);
                Assert.That(LeafBlock.Comment == "");
            }

            IReadOnlyPlaceholderInner PatternInner = (IReadOnlyPlaceholderInner)LeafBlock.PropertyToInner(nameof(BaseNode.IBlock.ReplicationPattern));

            Assert.That(PatternInner != null);

            IReadOnlyPlaceholderInner SourceInner = (IReadOnlyPlaceholderInner)LeafBlock.PropertyToInner(nameof(BaseNode.IBlock.SourceIdentifier));

            Assert.That(SourceInner != null);

            IReadOnlyPatternState PatternState = LeafBlock.PatternState;

            Assert.That(PatternState != null);
            if (PatternState != null)
            {
                Assert.That(PatternState.ParentInner == PatternInner);
                Assert.That(PatternState.ParentIndex == LeafBlock.PatternIndex);
            }

            IReadOnlySourceState SourceState = LeafBlock.SourceState;

            Assert.That(SourceState != null);
            if (SourceState != null)
            {
                Assert.That(SourceState.ParentInner == SourceInner);
                Assert.That(SourceState.ParentIndex == LeafBlock.SourceIndex);
            }

            Assert.That(MainLeafBlocksInner.FirstNodeState == LeafBlock.StateList[0]);

            IReadOnlyListInner MainLeafPathInner = (IReadOnlyListInner)RootState.PropertyToInner(nameof(Main.LeafPath));

            Assert.That(MainLeafPathInner != null);
            if (MainLeafPathInner != null)
            {
                Assert.That(!MainLeafPathInner.IsNeverEmpty);
                Assert.That(MainLeafPathInner.InterfaceType.IsTypeof <Leaf>());
                Assert.That(MainLeafPathInner.Count == 2);
                Assert.That(MainLeafPathInner.StateList != null);
                Assert.That(MainLeafPathInner.StateList?.Count == 2);
                Assert.That(MainLeafPathInner.FirstNodeState == MainLeafPathInner.StateList[0]);
                Assert.That(MainLeafPathInner.IndexAt(0) == MainLeafPathInner.FirstNodeState.ParentIndex);
                Assert.That(MainLeafPathInner.AllIndexes().Count == MainLeafPathInner.Count);
            }

            ReadOnlyNodeStateReadOnlyList AllChildren = RootState.GetAllChildren();

            Assert.That(AllChildren.Count == 19, $"New count: {AllChildren.Count}");

            IReadOnlyPlaceholderInner PlaceholderInner = (IReadOnlyPlaceholderInner)RootState.InnerTable[nameof(Main.PlaceholderLeaf)];

            Assert.That(PlaceholderInner != null);

            IReadOnlyBrowsingPlaceholderNodeIndex PlaceholderNodeIndex = (IReadOnlyBrowsingPlaceholderNodeIndex)PlaceholderInner.ChildState.ParentIndex;

            Assert.That(PlaceholderNodeIndex != null);
            Assert.That(Controller0.Contains(PlaceholderNodeIndex));

            IReadOnlyOptionalInner UnassignedOptionalInner = (IReadOnlyOptionalInner)RootState.InnerTable[nameof(Main.UnassignedOptionalLeaf)];

            Assert.That(UnassignedOptionalInner != null);

            IReadOnlyBrowsingOptionalNodeIndex UnassignedOptionalNodeIndex = UnassignedOptionalInner.ChildState.ParentIndex;

            Assert.That(UnassignedOptionalNodeIndex != null);
            Assert.That(Controller0.Contains(UnassignedOptionalNodeIndex));
            Assert.That(Controller0.IsAssigned(UnassignedOptionalNodeIndex) == false);

            IReadOnlyOptionalInner AssignedOptionalInner = (IReadOnlyOptionalInner)RootState.InnerTable[nameof(Main.AssignedOptionalLeaf)];

            Assert.That(AssignedOptionalInner != null);

            IReadOnlyBrowsingOptionalNodeIndex AssignedOptionalNodeIndex = AssignedOptionalInner.ChildState.ParentIndex;

            Assert.That(AssignedOptionalNodeIndex != null);
            Assert.That(Controller0.Contains(AssignedOptionalNodeIndex));
            Assert.That(Controller0.IsAssigned(AssignedOptionalNodeIndex) == true);

            int    Min, Max;
            object ReadValue;

            RootState.PropertyToValue(nameof(Main.ValueBoolean), out ReadValue, out Min, out Max);
            bool ReadAsBoolean = ((int)ReadValue) != 0;

            Assert.That(ReadAsBoolean == true);
            Assert.That(Controller0.GetDiscreteValue(RootIndex0, nameof(Main.ValueBoolean), out Min, out Max) == (ReadAsBoolean ? 1 : 0));
            Assert.That(Min == 0);
            Assert.That(Max == 1);

            RootState.PropertyToValue(nameof(Main.ValueEnum), out ReadValue, out Min, out Max);
            BaseNode.CopySemantic ReadAsEnum = (BaseNode.CopySemantic)(int) ReadValue;
            Assert.That(ReadAsEnum == BaseNode.CopySemantic.Value);
            Assert.That(Controller0.GetDiscreteValue(RootIndex0, nameof(Main.ValueEnum), out Min, out Max) == (int)ReadAsEnum);
            Assert.That(Min == 0);
            Assert.That(Max == 2);

            RootState.PropertyToValue(nameof(Main.ValueString), out ReadValue, out Min, out Max);
            string ReadAsString = ReadValue as string;

            Assert.That(ReadAsString == "s");
            Assert.That(Controller0.GetStringValue(RootIndex0, nameof(Main.ValueString)) == ReadAsString);

            RootState.PropertyToValue(nameof(Main.ValueGuid), out ReadValue, out Min, out Max);
            Guid ReadAsGuid = (Guid)ReadValue;

            Assert.That(ReadAsGuid == ValueGuid0);
            Assert.That(Controller0.GetGuidValue(RootIndex0, nameof(Main.ValueGuid)) == ReadAsGuid);

            ReadOnlyController Controller1 = ReadOnlyController.Create(RootIndex0);

            Assert.That(Controller0.IsEqual(CompareEqual.New(), Controller0));

            Assert.That(CompareEqual.CoverIsEqual(Controller0, Controller1));
        }
        static void BrowseNode(ReadOnlyController controller, IReadOnlyIndex index, Stats stats)
        {
            Assert.That(index != null, "ReadOnly #0");
            Assert.That(controller.Contains(index), "ReadOnly #1");
            IReadOnlyNodeState State = controller.IndexToState(index);

            Assert.That(State != null, "ReadOnly #2");
            Assert.That(State.ParentIndex == index, "ReadOnly #4");

            Node Node;

            if (State is IReadOnlyPlaceholderNodeState AsPlaceholderState)
            {
                Node = AsPlaceholderState.Node;
            }
            else if (State is IReadOnlyPatternState AsPatternState)
            {
                Node = AsPatternState.Node;
            }
            else if (State is IReadOnlySourceState AsSourceState)
            {
                Node = AsSourceState.Node;
            }
            else
            {
                Assert.That(State is IReadOnlyOptionalNodeState, "ReadOnly #5");
                IReadOnlyOptionalNodeState AsOptionalState = (IReadOnlyOptionalNodeState)State;
                IReadOnlyOptionalInner     ParentInner     = AsOptionalState.ParentInner;

                //Assert.That(ParentInner.IsAssigned, "ReadOnly #6");

                Node = AsOptionalState.Node;
            }

            stats.NodeCount++;

            Type           ChildNodeType;
            IList <string> PropertyNames = NodeTreeHelper.EnumChildNodeProperties(Node);

            foreach (string PropertyName in PropertyNames)
            {
                if (NodeTreeHelperChild.IsChildNodeProperty(Node, PropertyName, out ChildNodeType))
                {
                    stats.PlaceholderNodeCount++;

                    IReadOnlyPlaceholderInner Inner      = (IReadOnlyPlaceholderInner)State.PropertyToInner(PropertyName);
                    IReadOnlyNodeState        ChildState = Inner.ChildState;
                    IReadOnlyIndex            ChildIndex = ChildState.ParentIndex;
                    BrowseNode(controller, ChildIndex, stats);
                }

                else if (NodeTreeHelperOptional.IsOptionalChildNodeProperty(Node, PropertyName, out ChildNodeType))
                {
                    stats.OptionalNodeCount++;

                    NodeTreeHelperOptional.GetChildNode(Node, PropertyName, out bool IsAssigned, out Node ChildNode);
                    Debug.Assert(ChildNode is not null);
                    //if (IsAssigned)
                    {
                        if (IsAssigned)
                        {
                            stats.AssignedOptionalNodeCount++;
                        }

                        IReadOnlyOptionalInner Inner      = (IReadOnlyOptionalInner)State.PropertyToInner(PropertyName);
                        IReadOnlyNodeState     ChildState = Inner.ChildState;
                        IReadOnlyIndex         ChildIndex = ChildState.ParentIndex;
                        BrowseNode(controller, ChildIndex, stats);
                    }

                    /*else
                     *  stats.NodeCount++;*/
                }

                else if (NodeTreeHelperList.IsNodeListProperty(Node, PropertyName, out ChildNodeType))
                {
                    stats.ListCount++;

                    IReadOnlyListInner Inner = (IReadOnlyListInner)State.PropertyToInner(PropertyName);

                    for (int i = 0; i < Inner.StateList.Count; i++)
                    {
                        stats.PlaceholderNodeCount++;

                        IReadOnlyPlaceholderNodeState ChildState = Inner.StateList[i];
                        IReadOnlyIndex ChildIndex = ChildState.ParentIndex;
                        BrowseNode(controller, ChildIndex, stats);
                    }
                }

                else if (NodeTreeHelperBlockList.IsBlockListProperty(Node, PropertyName, /*out Type ChildInterfaceType,*/ out ChildNodeType))
                {
                    stats.BlockListCount++;

                    IReadOnlyBlockListInner Inner = (IReadOnlyBlockListInner)State.PropertyToInner(PropertyName);

                    for (int BlockIndex = 0; BlockIndex < Inner.BlockStateList.Count; BlockIndex++)
                    {
                        IReadOnlyBlockState BlockState = Inner.BlockStateList[BlockIndex];

                        stats.PlaceholderNodeCount++;
                        BrowseNode(controller, BlockState.PatternIndex, stats);

                        stats.PlaceholderNodeCount++;
                        BrowseNode(controller, BlockState.SourceIndex, stats);

                        for (int i = 0; i < BlockState.StateList.Count; i++)
                        {
                            stats.PlaceholderNodeCount++;

                            IReadOnlyPlaceholderNodeState ChildState = BlockState.StateList[i];
                            IReadOnlyIndex ChildIndex = ChildState.ParentIndex;
                            BrowseNode(controller, ChildIndex, stats);
                        }
                    }
                }

                else
                {
                    Type         NodeType = Type.FromGetType(Node);
                    PropertyInfo Info     = NodeType.GetProperty(PropertyName);

                    if (Info.PropertyType.IsTypeof <Document>())
                    {
                    }
                    else if (Info.PropertyType.IsTypeof <bool>())
                    {
                    }
                    else if (Info.PropertyType.IsEnum)
                    {
                    }
                    else if (Info.PropertyType.IsTypeof <string>())
                    {
                    }
                    else if (Info.PropertyType.IsTypeof <Guid>())
                    {
                    }
                    else
                    {
                        Assert.That(false, $"State Tree unexpected property: {Info.PropertyType.Name}");
                    }
                }
            }
        }