Why isn't this recursion working in C#?

Question

public static bool AllNodesChecked(TreeNodeCollection nodes)        
{
    foreach (TreeNode node in nodes)
    {
        if (!node.Checked)
        {
            return false;
        }
        AllNodesChecked(node.Nodes);
    }
    return true;
}

Test tree is

A1(checked) -> B1(unchecked)
A2(checked)
A3(checked)

but it isn't returning when it hits node B1.

EDIT: Thank you all for helping my tired brain. Recursion should only be attempted early in the day after a cold shower.

Answer 1

You are ignoring the return value of AllNodesChecked in the recursive call:

public static bool AllNodesChecked(TreeNodeCollection nodes)        
{
    foreach (TreeNode node in nodes)
        if (!node.Checked || !AllNodesChecked(node.Nodes))
           return false;
    return true;
}

The return statement only returns from the current method in the call stack to the immediate caller. It doesn't suddenly return from all other calls above in the call stack.

Answer 2

Change:

AllNodesChecked(node.Nodes); 

To:

if(!AllNodesChecked(node.Nodes))
    return false;

Answer 3

Try this:

public static bool AllNodesChecked(TreeNodeCollection nodes)         
{ 
    foreach (TreeNode node in nodes) 
    { 
        if (node.Checked == false || !AllNodesChecked(node.Nodes)) 
        { 
            return false; 
        } 
    } 
    return true; 
} 

Answer 4

You're not evaluating the result of the recursive call to check child nodes.

Answer 5

I would take a slightly different approach here. What I'd do is I'd first write code that turns your tree (which I assume really is a tree, not an arbitrary graph) into a sequence of nodes. Something like:

static IEnumerable<Node> AllNodes(this Node node)
{
    var stack = new Stack<Node>();
    stack.Push(node);
    while(stack.Count > 0)
    {
        var current = stack.Pop();
        yield return current;
        foreach(var child in current.Nodes)
            stack.Push(child);
    }
}

and now you can use sequence operators:

bool allChecked = root.AllNodes().All(x=>x.Checked);

No recursion, no problem.