有人知道为什么我在尝试处理 Reaction 时会收到此 NullReferenceException 错误

Question

所以我正在为我的 Discord 服务器创建一个 Discord Bot，但我不知道为什么它不起作用。我认为问题出在我的 ReactionHandler 中，但我不确定是什么原因造成的？

我试图修改一些代码..但我无法弄清楚所以我想问问是否有人知道我的代码有什么问题......我的代码可能很乱，但我希望它不介意你。我不会展示我的 "Commands" 脚本，因为它与这个问题无关！

private async Task Client_CheckTicket(SocketMessage arg)
{
    try
    {
        var Message = arg as SocketUserMessage;
        var Context = new SocketCommandContext(Client, Message);
        if (Context.Channel.Id == debugchannel)
        {
            Console.WriteLine("Detected a debug message i wont be taking any actions against it");
            return;
        }

        if (Context.User.IsBot)
        {
            String s = "";
            String path = @"C:\Users\Alex\source\repos\discbot\ids.txt";

            using (StreamReader sr = File.OpenText(path))
            {
                try
                {
                    while ((s = sr.ReadLine()) != null)
                    {
                        await DebugMessage("Checking this message: " + Message.Content);
                        if (Context.Message.Content.Contains(s))
                        {
                            messageid = Message.Id;
                            await DebugMessage("added");
                        }

                    }

                }
                catch (Exception e)
                {
                    await DebugMessage("Something went wrong... Exception was sent to console!");
                    Console.WriteLine(e);
                    return;
                }
                sr.Close();

            }
            if (messageid != 0)
            {
                path = @"C:\Users\Alex\source\repos\discbot\messageid.txt";
                using (StreamWriter sr = File.AppendText(path))
                {
                    sr.WriteLine(messageid);
                    sr.Close();
                }
            }
            else
            {
                await DebugMessage("MessageID was 0 so i will not add it to my database");
                return;
            }

        }
        else
        {
            await DebugMessage("No pass");
        }
    } catch(Exception e)
    {
       await DebugMessage(e.ToString());
    }
}

完整代码： https://pastebin.com/RrcBTdr0

我从输出调试中得到的错误：

Exception thrown: 'System.NullReferenceException' in discbot.dll
Exception thrown: 'System.NullReferenceException' in System.Private.CoreLib.dll

在控制台上我得到：

26.6.2019 17.20.10 at Gateway A ReactionAdded handler has thrown an unhandled exception.

我希望当将特定反应添加到 "Ticket"

时，机器人会向特定频道发送消息

没有 "Client.MessageReceived += Client_CheckTicket" 和 "Client.ReactionAdded += OnReactionAdded;" 其他代码工作正常。但是当我把它们加回去时，东西就刹车了……

注意：我没有在 OnReactionAdded 上收到 DebugMessages，所以执行是否有问题？

private async Task OnReactionAdded(Cacheable<IUserMessage, ulong> cache, ISocketMessageChannel channel, SocketReaction thereaction)
        {
            await DebugMessage("React func started");

难道当我assign/create一个新变量时它会因为内存占用而覆盖另一个变量？

MessageRecever（我打错了）：

private async Task Client_MessageReceived(SocketMessage arg)
        {

            var Message = arg as SocketUserMessage;
            await ReactAsync(Message);
            var Context = new SocketCommandContext(Client, Message);

            if (Context.Message == null || Context.Message.Content == "") return;
            if (Context.User.IsBot) return;

            int ArgPos = 0;
            if (!(Message.HasStringPrefix("nuked!", ref ArgPos) || Message.HasMentionPrefix(Client.CurrentUser, ref ArgPos))) return;


            var Result = await Commands.ExecuteAsync(Context, ArgPos, null);
            if (!Result.IsSuccess)
            {
                Console.WriteLine($"{DateTime.Now} at Commands Something went wrong with executing a nuke launch. Text: {Context.Message.Content} | Error: {Result.ErrorReason}");
                await Context.Channel.SendMessageAsync($"{DateTime.Now} at Commands Something went wrong with executing a nuke launch. Text: {Context.Message.Content} | Error: {Result.ErrorReason}");
            }

        }

我已经尝试更多地定位问题，我认为它就在这里：

 using (StreamReader sr = File.OpenText(path))
                    {
                        try
                        {
                            while ((s = sr.ReadLine()) != null)
                            {
                                DebugMessage("Checking this message: " + Message.Content);
                                if (Context.Message.Content.Contains(s))
                                {
                                    messageid = Message.Id;
                                    DebugMessage("added");
                                }

                            }

                        }
                        catch (Exception e)
                        {
                            DebugMessage("Something went wrong... Exception was sent to console!");
                            Console.WriteLine(e);
                            return;
                        }
                        sr.Close();

                    }

最后我得到了一些更具体的错误：

System.NullReferenceException: Object reference not set to an instance of an object. at discbot.Program.DebugMessage(String a) in C:\Users\Alex\source\repos\discbot\discbot\Program.cs:line 103 at discbot.Program.Client_CheckTicket(SocketMessage arg) in C:\Users\Alex\source\repos\discbot\discbot\Program.cs:line 222

第 103 行：await Client.GetGuild(593114638770634763).GetTextChannel(593430696874213384).SendMessageAsync(a);

第 222 行：await DebugMessage("No pass");

是的，这是一个 nullreference 错误，有很多答案，但我无法弄清楚..

Console.WriteLine(a);
            await Client.GetGuild(593114638770634763).GetTextChannel(593430696874213384).SendMessageAsync(a);

WriteLine 有效，但 SenmessageAsync returns NullReferenceException.. 我检查了我的服务器 ID 和我的频道 ID 是正确的...

所以问题出在：

public async Task DebugMessage(string a)
        {
            Console.WriteLine(a);
            await Client.GetGuild(593114638770634763).GetTextChannel(593430696874213384).SendMessageAsync(a);

        }

空错误发生在： Client.GetGuild(593114638770634763).GetTextChannel(593430696874213384).SendMessageAsync(a);

因为当我执行 await DebugMessage("No pass"); 时 Console.WriteLine 有效但第二个无效？知道为什么它不起作用吗？

字符串 "a" 不是原因，因为我用这个替换了 a 变量： await Client.GetGuild(593114638770634763).GetTextChannel(593430696874213384).SendMessageAsync("ok");

还是不行...

如果您仍然不明白哪个部分坏了，那就是：

await Client.GetGuild(593114638770634763).GetTextChannel(593430696874213384).SendMessageAsync(The variable is not causing this...);

现在我这样设置:

public async Task DebugMessage(string a)
        {
            Console.WriteLine("Getting server");
            var server =  Client.GetGuild(593114638770634763);
            Console.WriteLine("Getting chat");
            var chat = server.GetTextChannel(593430696874213384);
            Console.WriteLine("Writing to Chat");
            await chat.SendMessageAsync(a);
            Console.WriteLine("Succeeded");

        }

它失败了： await chat.SendMessageAsync(a);

Answer 1

"Because chat is null... most likely because your ID is incorrect and no channel with a matching ID can be found in that guild." -Anu6is 这有效....

有人知道为什么我在尝试处理 Reaction 时会收到此 NullReferenceException 错误

Does somebody know why i get this NullReferenceException error when trying to handle a Reaction

c#

discord.net