public void Undo()
{
if (!Executed)
{
throw new CommandNotExecutedException();
}
if (!_Db.RemoveNode(_NewNode))
{
throw new CommandFailedDbWriteException();
}
_ParentNode.RemoveChild(_NewNode);
_NewNode.RemoveParent(_ParentNode);
Executed = false;
}
public void Execute()
{
if (Executed)
{
throw new CommandAlreadyExecutedException();
}
if (!_Db.RemoveNode(_RemoveNode))
{
throw new CommandFailedDbWriteException();
}
//Make note of any links between the node's parents and the node's children
//We need this information to rebuild these links if we undo the command
foreach (var parent in _RemoveNode.ParentNodes)
{
foreach (var parentChild in parent.ChildNodes)
{
foreach (var child in _RemoveNode.ChildNodes)
{
if (ReferenceEquals(parentChild, child))
{
_ParentChildLinks.Add(parent, parentChild);
}
}
}
}
//Link up each of the node's children to each of the node's parents
foreach (var node in _RemoveNode.ChildNodes)
{
_Children.Add(node);
foreach (var parent in _RemoveNode.ParentNodes)
{
node.AddParent(parent);
}
node.RemoveParent(_RemoveNode);
}
//Link up each of the node's parents to each of the node's children
foreach (var parent in _RemoveNode.ParentNodes)
{
_Parents.Add(parent);
foreach (var node in _RemoveNode.ChildNodes)
{
parent.AddChild(node);
}
parent.RemoveChild(_RemoveNode);
}
//Remove eacho f the node's children
foreach (var node in _Children)
{
_RemoveNode.RemoveChild(node);
}
//Remove each of the node's parents
foreach (var parent in _Parents)
{
_RemoveNode.RemoveParent(parent);
}
Executed = true;
}