How do I Backtrack a Stack-Based Depth First Search - search

Question

I am trying to implement a DFS algorithm to work in a maze. The maze has walls. The DFS gets stuck in a corner and does not backtrack therefore it results in an infinite loop. How should I rewrite my code to get it to backtrack. This is code for a space-search type of DFS.
Depth-First-Search Function
public List<Node<Point2D>> DFS(Problem p)
{
Node<Point2D> root = new Node<Point2D>() { Data = p.initial, Parent = null };
frontierStack.Push(root);
while (frontierStack.Count > 0 && explored.Count < 55)
{
Node<Point2D> currentNode = frontierStack.Pop();
explored.Add(currentNode.Data.ToString());
Console.WriteLine(currentNode);
//Debug.WriteLine(explored.Count);
foreach (string action in p.Action)
{
if (p.Result(currentNode.Data, action) != null)
{
Node<Point2D> adjacentNode
= new() { Data = p.Result(currentNode.Data, action), Parent = currentNode };
if (explored.Contains(adjacentNode.Data.ToString()) == false || frontierStack.Contains(adjacentNode) == false)
{
if (p.GoalTest(adjacentNode.Data) == true)
{
return GetNodes(adjacentNode);
}
}
frontierStack.Push(adjacentNode);
}
}
}
return null;
}
Here is Where it gets stuck:
The black line is the path it took, the blue 'X' are walls and the red 'X' is where it gets stuck at point (1,3) - (1,4). I have been trying to resolve this for a few hours now. Nothing seems to be working. I am still a beginner so sorry for asking something so trivial and thank you for your help in advance.

Answer 1

Solved it. Hope this is useful for other beginners out there.
Updated DFS Algorithm
foreach (string action in p.Action)
{
if (p.Result(currentNode.Data, action) != null)
{
Node<Point2D> adjacentNode = new() {
Data = p.Result(currentNode.Data, action),
Parent = currentNode
};
frontierStack.Push(adjacentNode);
if (explored.Contains(adjacentNode.Data.ToString()) == false || frontierStack.Contains(adjacentNode) == false)
{
if (p.GoalTest(adjacentNode.Data) == true)
{
return GetNodes(adjacentNode);
}
}
else if (explored.Contains(adjacentNode.Data.ToString()) == true && frontierStack.Contains(adjacentNode) == true)
{
frontierStack.Pop();
}
}
}
Add the else if to check if it is either visited/explored and still in the frontier.