VB.NET中Telegram Bot V18接收消息报错问题求助

需要修改的核心点 #

• 异步方法类型修正：Telegram Bot V18的StartReceiving要求更新和错误处理方法是返回Task的异步函数，而非异步Sub。异步Sub无法匹配框架要求的委托类型，这是参数报错的直接原因。
• 数据类型修正：update.Message.Chat.Id是Long类型，不能直接赋值给String变量，会引发类型转换错误。
• 接收配置优化：显式指定AllowedUpdates，只接收需要的更新类型，避免不必要的资源消耗。

修改后的完整可运行代码 #

Imports Telegram.Bot
Imports Telegram.Bot.Exceptions
Imports Telegram.Bot.Polling
Imports Telegram.Bot.Types
Imports Telegram.Bot.Types.Enums
Imports System.Threading

Public Class Form1

    Public TelegramBotToken As String = "YOUR TELEGRAM TOKEN HERE"
    Private cancellationTokenSource As CancellationTokenSource

    Private Sub Button4_Click(sender As Object, e As EventArgs) Handles Button4.Click
        cancellationTokenSource = New CancellationTokenSource()
        Dim bot1 = New TelegramBotClient(TelegramBotToken)
        
        Dim receiverOptions1 = New ReceiverOptions With {
            .AllowedUpdates = {UpdateType.Message} '仅接收消息类型更新
        }

        bot1.StartReceiving(
            updateHandler:=AddressOf UpdateHandler,
            pollingErrorHandler:=AddressOf ErrorHandler,
            receiverOptions:=receiverOptions1,
            cancellationToken:=cancellationTokenSource.Token
        )
    End Sub

    Private Async Function ErrorHandler(botClient As ITelegramBotClient, exception As Exception, ct As CancellationToken) As Task
        '添加错误日志逻辑，可根据需求输出到控制台或窗体控件
        Dim errorMsg = $"错误类型: {exception.GetType().Name}, 消息: {exception.Message}"
        Console.WriteLine(errorMsg)
        
        '处理API专属错误，获取更多细节
        If TypeOf exception Is ApiRequestException Then
            Dim apiEx = DirectCast(exception, ApiRequestException)
            Console.WriteLine($"API错误码: {apiEx.ErrorCode}, 描述: {apiEx.Description}")
        End If
    End Function

    Private Async Function UpdateHandler(botClient As ITelegramBotClient, update As Update, ct As CancellationToken) As Task
        If update.Type = UpdateType.Message Then
            Dim message = update.Message
            If message.Type = MessageType.Text Then
                Dim text As String = message.Text
                Dim chatId As Long = message.Chat.Id '修正为正确的Long类型
                Dim username As String = If(message.Chat.Username, "无用户名") '处理空用户名情况

                '将消息内容同步到窗体控件（避免跨线程操作报错）
                Me.Invoke(Sub()
                              TextBox1.Text = $"收到消息: {text}{Environment.NewLine}" &
                                             "Chat ID: " & chatId & Environment.NewLine &
                                             "用户名: " & username
                          End Sub)
            End If
        End If
    End Function

    '窗体关闭时优雅停止Bot接收任务
    Private Sub Form1_FormClosing(sender As Object, e As FormClosingEventArgs) Handles MyBase.FormClosing
        cancellationTokenSource?.Cancel()
    End Sub
End Class

关键细节说明 #

1. 异步函数的必要性：VB.NET中异步Sub仅适用于事件触发场景，而Telegram Bot框架需要通过返回Task来追踪异步操作的执行状态，确保消息处理流程的可靠性。
2. 取消令牌管理：通过CancellationTokenSource可以在窗体关闭或需要停止Bot时，安全终止接收任务，避免资源泄漏。
3. 跨线程操作处理：在WinForm环境中，更新UI控件必须通过Invoke方法切换到主线程，否则会引发跨线程操作异常。

内容的提问来源于stack exchange，提问作者Paul Falleyn