c# - 找不到这个 NullReferenceException 的原因

Question

我有以下方法:

internal static void removeMethodFromTag(byte p, Method method)
        {
            Console.WriteLine("Remove method " + method.getName() + " from the tag");
            List<Method> outList = new List<Method>();
            methodTaggings.TryGetValue(p, out outList);
            Console.WriteLine(outList.Count);
            outList.Remove(method);
            methodTaggings.Remove(p);
            methodTaggings.Add(p, outList);
        }

这是字典方法标签:

private static Dictionary<byte, List<Method>> methodTaggings = new Dictionary<byte, List<Method>>();

现在我总是在行中得到一个NullReferenceException

Console.WriteLine(outList.Count);

但我不明白为什么？即使我在字典中找不到值，列表也不应该为空？

Answer 1

这不应该是:

internal static void removeMethodFromTag(byte p, Method method)
        {
            Console.WriteLine("Remove method " + method.getName() + " from the tag");
            List<Method> outList = new List<Method>();
            if (methodTaggings.TryGetValue(p, out outList);
            {
              Console.WriteLine(outList.Count);
              outList.Remove(method);
              methodTaggings.Remove(p);
              methodTaggings.Add(p, outList);
           }
        }