c# - Azure Web 作业中的异步调用后 TextWriter 意外关闭

Question

我创建了一个简单的 Azure WebJob，它调用异步任务，并尝试使用 TextWriter 来记录一些信息。 在调用异步任务之前写入日志没问题，但在调用之后，TextWriter 将关闭。在下面的示例代码中，我只是调用 Task.Delay() 来演示。

如果我将 await log.WriteLineAsync("") 调用更改为 log.WriteLine("")

也没关系

public class Program
{
    // Please set the following connection strings in app.config for this WebJob to run:
    // AzureWebJobsDashboard and AzureWebJobsStorage
    static void Main()
    {
        JobHostConfiguration config = new JobHostConfiguration();
        JobHost host = new JobHost(config);
        host.Call(typeof (Program).GetMethod("DoJobNow"), new { value = "Hello world!" });
        host.RunAndBlock();
    }


    [NoAutomaticTrigger]
    public async static void DoJobNow(string value, TextWriter log)
    {
        await log.WriteLineAsync("Write with textwriter");
        await log.WriteLineAsync("Write with textwriter again - still open");
        await Task.Delay(100);
        await log.WriteLineAsync("TextWriter is closed?? Exception here!");

    }
}

当我在本地运行此代码时，我在最后一次日志调用中收到 System.ObjectDisposeException ，如果我对 Task.Delay 行进行评论，它工作正常! 这是为什么？

Answer 1

您需要设置DoJobNow的返回类型以返回Task。调用线程将导致 TextWriter 被释放

[NoAutomaticTrigger]
public async static Task DoJobNow(string value, TextWriter log)
{
    await log.WriteLineAsync("Write with textwriter");
    await log.WriteLineAsync("Write with textwriter again - still open");
    await Task.Delay(100);
    await log.WriteLineAsync("TextWriter is closed?? Exception here!");
}