如何修复Unity2017端口项目Unity 4.x

Question

How can fix this error that occurs when trying to port a Unity 4.x project to Unity2017?

Error CS0177: The out parameter `result' must be assigned to before control leaves the current method

public bool TryDequeue(out T result)
{
    Node<T> curHead;
    Node<T> curTail;
    Node<T> next;
    do
    {
        curHead = _head;
        curTail = _tail;
        next = curHead.Next;
        if (curHead == _head)
        {
            if (next == null)
            {
                result = default(T);
                return false;
            }
            if (curHead == curTail)
            {
                Interlocked.CompareExchange<Node<T>>(ref _tail, next, curTail); 
            }
            else
            {
                result = next.Item; 
                if (Interlocked.CompareExchange<Node<T>>(ref _head, 
                    next, curHead) == curHead)
                    break;
            }
        }
    }
    while (true);
    return true;
}

Answer 1

An out parameter must be assigned some value, before the control leaves the function.

In your case, the compiler can't determine whether your variable will be assigned or not, because it is being assigned inside of an if statement.

Make sure the parameter is assigned a value in all possible cases or add a default value (start of the method) to make sure it will be assigned at least once.