Use Manual Navigation

What you should know beforehand:

PSI
ShellLocks

Examples (?):

In some cases it might be useful to manually navigate the syntax tree (relatively to a particular tree node). For this purpose, any tree node has a number of properties and methods, like:

Parent: returns a parent tree node;
Children: returns IEnumerable with children nodes;
NextSibling, PrevSibling: next and previous sibling tree nodes;
lots of them.

For example, let's create an ITreeNode extension method that walks up the syntax tree and finds (if there are any) a parent tree node of a particular type:

[CanBeNull]
public static T GetParentOfType<T>(this ITreeNode node) where T : class, ITreeNode
{
    while (node != null)
    {
        var typedNode = node as T;
        if (typedNode != null)
            return typedNode;

        node = node.Parent;                                                                
    }
    return null;
}

For example, we can use it to navigate to the method declaration while standing anywhere inside a method:

private IShellLocks _shellLocks;
private NodeUnderCaretNavigator _navigator;
  
...
  
public void NavigateToParentMethod()
{
    _shellLocks.ExecuteOrQueueReadLock(_lifetime, "NavigateToParent", () =>
    {
        var node = _navigator.GetTreeNodeUnderCaret;
        var parentMethod = node.GetParentOfType<IMethodDeclaration>();
        parentMethod?.NavigateToTreeNode(true);
    });
}

Notes

We use the GetTreeNodeUnderCaret() method of the NodeUnderCaretNavigator class shown in Get a Tree Node Under Caret.
Note that to prevent conflicts with user input during the navigation, we must obtain the read lock before calculating the node under the caret. This is done by means of the special method of the IShellLocks interface: _shellLocks.QueueReadLock(...).

Last modified: 20 April 2023