C# Error message: Not all code paths return a value

Question

My code is for searching a Binary Tree for the same value given.

To me it is returning a value.

Any ideas/help?

public Boolean ContainsValue (Node<T> tree, int value)
{
    if (tree == null)
        return false;

    if (tree.Data.Equals(value))
        return true;

    if (value.CompareTo(tree.Data) < 0)
        return ContainsValue(tree.Left, value);

    if (value.CompareTo(tree.Data) > 0)
        return ContainsValue(tree.Right, value);
}

EDIT: Thanks I realised what I did wrong once you all mentioned the problem. (I now feel very silly)

What if none of your if statement won't work? Your method does not return anything. — Soner Gönül
– Soner Gönül, Commented Jan 18, 2014 at 17:00

Sergey Berezovskiy · Accepted Answer · 2014-01-18 16:58:51Z

You need default (unconditional) return for case when none of conditions was satisfied:

public Boolean ContainsValue (Node<T> tree, int value)
{
    if (tree == null)
        return false;

    if (tree.Data.Equals(value))
        return true;

    if (value.CompareTo(tree.Data) < 0)
        return ContainsValue(tree.Left, value);

    if (value.CompareTo(tree.Data) > 0)
        return ContainsValue(tree.Right, value);

    // here
    // return some_value;
    // or throw exception
}

I think your code should look like:

public bool ContainsValue (Node<T> tree, int value)
{
    if (tree == null)
        return false;

    if (tree.Data.Equals(value))
        return true;

    if (value.CompareTo(tree.Data) < 0)
        return ContainsValue(tree.Left, value);

    // thus you already verified case when value is less or equal to data
    // you don't need if condition here
    return ContainsValue(tree.Right, value);
}

dursk · Accepted Answer · 2014-01-18 16:59:21Z

1

You need a default return value for the method. Your only return values are in IF statements, so the compiler will complain, even if we as humans can see that at least one IF statement will execute.

answered Jan 18, 2014 at 16:59

dursk

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