/// <summary>
/// Expands the current branch if possible
/// </summary>
public void Expand()
{
if (ChildBranches == null)
{
FetchChildren();
}
if (ChildBranches.Any())
{
IsExpanded = true;
}
}
/// <summary>
/// Refreshes cached knowledge in this branch e.g. what children an object has
/// </summary>
/// <param name="startAtTop">True to also refresh all <see cref="Parent"/>
/// branches (starting with the root)</param>
public void Refresh(bool startAtTop)
{
// if we must go up and refresh from the top down
if (startAtTop)
{
Parent?.Refresh(true);
}
// we don't want to loose the state of our children so lets be selective about how we refresh
//if we don't know about any children yet just use the normal method
if (ChildBranches == null)
{
FetchChildren();
}
else
{
// we already knew about some children so preserve the state of the old children
// first gather the new Children
var newChildren = tree.TreeBuilder?.GetChildren(this.Model) ?? Enumerable.Empty <T> ();
// Children who no longer appear need to go
foreach (var toRemove in ChildBranches.Keys.Except(newChildren).ToArray())
{
ChildBranches.Remove(toRemove);
//also if the user has this node selected (its disapearing) so lets change selection to us (the parent object) to be helpful
if (Equals(tree.SelectedObject, toRemove))
{
tree.SelectedObject = Model;
}
}
// New children need to be added
foreach (var newChild in newChildren)
{
// If we don't know about the child yet we need a new branch
if (!ChildBranches.ContainsKey(newChild))
{
ChildBranches.Add(newChild, new Branch <T> (tree, this, newChild));
}
else
{
//we already have this object but update the reference anyway incase Equality match but the references are new
ChildBranches [newChild].Model = newChild;
}
}
}
}
/// <summary>
/// Returns true if the current branch can be expanded according to
/// the <see cref="TreeBuilder{T}"/> or cached children already fetched
/// </summary>
/// <returns></returns>
public bool CanExpand()
{
// if we do not know the children yet
if (ChildBranches == null)
{
//if there is a rapid method for determining whether there are children
if (tree.TreeBuilder.SupportsCanExpand)
{
return(tree.TreeBuilder.CanExpand(Model));
}
//there is no way of knowing whether we can expand without fetching the children
FetchChildren();
}
//we fetched or already know the children, so return whether we have any
return(ChildBranches.Any());
}
