.NET Framework 4.6中HttpClient.PostAsJsonAsync调用无响应问题求助

调试模式下运行项目，执行到PingServerAsync方法中的以下代码时：

var response = await httpClient.PostAsJsonAsync(url, payload);

程序短暂卡顿后直接退出，既不返回响应值，也未触发异常，相关日志也未记录响应信息。

相关代码 #

CheckDicomServersAsync方法 #

public async Task CheckDicomServersAsync(string hostName)
{
     ...
     var cstore = result.FirstOrDefault();
     MqttService.applog.Debug($"****** Gonna Dicom Echo this - {cstore.ClientAETitle} *******");
    string resp = await PingDicomServerAsync(cstore);
    Console.WriteLine($"Dicom Echo response: {resp}");
}

PingServerAsync方法 #

private async Task<string> PingServerAsync(DICOMClient client)
{
    EchoViewModelSettings payload = new EchoViewModelSettings();
    payload.ClientAE = client.ClientAETitle;
    // 其他属性赋值...           
    
    using (httpClient)
    {
        httpClient.BaseAddress = new Uri(m_appConfig.DICOM_URL);
       
        var requestUri = handler + "/Echo?SessionID=" + System.Web.HttpUtility.UrlEncode(session.SessionID.ToString());

        try
        {
            MqttService.applog.Debug($"Make request: {requestUri}");

            var url = "http://localhost/MyDicomAPI/api/dicom/Echo?SessionID=my_session";

            // 发送POST请求
            var response = await httpClient.PostAsJsonAsync(url, payload);                    

            MqttService.applog.Debug($"The Response: {response.Content}");

            if (response.IsSuccessStatusCode)
            {
                var echoResponse = await response.Content.ReadAsStringAsync();
                MqttService.applog.Debug($"The Echo Response is: {echoResponse}");
            }                    
            if (response.StatusCode == System.Net.HttpStatusCode.OK)
            {
                Console.WriteLine(response.StatusCode.ToString());
                return response.StatusCode.ToString();
            }
            else
            {
                return response.StatusCode.ToString();
            }
        }
        catch (Exception ex)
        {
            MqttService.applog.Error($"WTF is wrong now: {ex}");
            throw;
        }
    }
}

Postman测试验证 #

使用Postman调用相同的URL和JSON请求体，能够正常返回响应（值为0表示成功）：

更新：补充调用链（临时绕过Windows服务） #

Program.cs代码 #

// Program.cs
static void Main()
{
    // 注释掉Windows服务启动代码
    //ServiceBase[] ServicesToRun;
    //ServicesToRun = new ServiceBase[]
    //{
    //    new MqttService()
    //};
    //ServiceBase.Run(ServicesToRun);

    MqttService mqttSvc = new MqttService(); // 调试版本
    
    mqttSvc.StartDebugMode();
}

MqttService.cs代码 #

// MqttService.cs
public void StartDebugMode()
{
    Init();

    this.CheckOtherServers(hostName);

    // 注释掉其他服务启动代码
    //StartSubscriber();
    //StartPublisher();
    //PublishHeartBeat(null, null);            
}

private async void CheckOtherServers(string hostName)
{
    if (this.pingDicom)
    {
        DicomStatus dicom = new DicomStatus();
        await dicom.CheckDicomServersAsync(hostName);
    }
}

内容的提问来源于stack exchange，提问作者bob.mazzo