Get a Tree Node by Reference

What you should know beforehand:

PSI
ShellLocks

Examples (?):

This is useful in case you need to navigate to an element that is referenced by a particular tree node (e.g., from a usage to a declaration).

So, the task is to obtain the reference you need. For example, we want to create a navigation from a particular expression to a declaration (the example is quite useless as it duplicates ReSharper's functionality, nevertheless, it perfectly illustrates the usage of references).

Let's make this as an extension method for ITreeNode:

[CanBeNull]
public static IEnumerable<IDeclaredElement> GetReferencedElements(this ITreeNode node)
{
    var result = new List<IDeclaredElement>();
    var parentExpression = node.GetParentOfType<IReferenceExpression>();
    if (parentExpression == null) return null;            
                          
    var references = parentExpression.GetReferences();            
 
    foreach (var reference in references)
    {
        var declaredElement = reference.Resolve().DeclaredElement;
        if (declaredElement != null)
            result.Add(declaredElement);
    }
 
    return result.Count == 0 ? null : result;
}

Now, it can be used to navigate to the first referenced element of the tree node under the caret (it would be always a declaration):

private IShellLocks _shellLocks;
private NodeUnderCaretNavigator _navigator;
 
// ...
 
public void NavigateToFirstReferencedElement()
{
    _shellLocks.ExecuteOrQueueReadLock(_lifetime, "NavigateByReference", () =>
    {
        var node = _navigator.GetTreeNodeUnderCaret();
        var referencedElements = node.GetReferencedElements();
        var element = referencedElements?.FirstNotNull();
        element?.Navigate(true);
    });
}

Notes

We use the GetTreeNodeUnderCaret() method of the NodeUnderCaretNavigator class shown in Get a Tree Node Under Caret.
We use the GetParentOfType method from Use Manual Navigation to obtain an IReferenceExpression instance.
The GetReferences method returns the list of references.
The IReference interface provides the Resolve method that allows getting a declared element from a reference.
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: 04 July 2023