为什么是ResponseMessage ?在await PostAsJsonAsync请求后，内容始终为空

我们正在向API发布一个"maintenanceEvent"，该API在ResponseMessage.Content中始终返回[]。如果我在这里写的代码有问题，我需要一些专家的指导。

private async Task SendMaintenanceEvent(object maintenanceEvent, MaintenanceEventType maintenanceEventType)
{
    string endpointAddress = "TheEndpointURI";
    string credentials = "OurCredentials";
    string credentialsBase64 = Convert.ToBase64String(System.Text.ASCIIEncoding.ASCII.GetBytes(credentials));
    // Convert the maintenanceEvent object to consumable JSON, then encode it to a StringContent object.
    this.responseInfo.MaintenanceEventAsJSON = System.Web.Helpers.Json.Encode(maintenanceEvent);
    StringContent stringContent = new StringContent(this.responseInfo.MaintenanceEventAsJSON, Encoding.UTF8, "application/json");
    using (HttpClient httpClient = new HttpClient())
    {
        httpClient.BaseAddress = new Uri(endpointAddress);
        httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Basic", credentialsBase64);
        this.responseInfo.AuthorizationHeader = httpClient.DefaultRequestHeaders.Authorization.ToString();
        this.responseInfo.EndpointUri = httpClient.BaseAddress.AbsoluteUri;
        // The async post.
        this.responseInfo.ResponseMessage = await httpClient.PostAsJsonAsync(access.EndpointDirectory, stringContent).ConfigureAwait(false);
        this.responseInfo.ResponseStatusCode = (int)this.responseInfo.ResponseMessage.StatusCode;
        // Consistently returns true so long as my credentials are valid.
        // When the auth credentials are invalid, this returns false.
        if (this.responseInfo.ResponseMessage.IsSuccessStatusCode)
        {
            // I expect to see some data from the service.
            this.responseInfo.ResponseContent = this.responseInfo.ResponseMessage.Content.ReadAsStringAsync();
        }
    }
}

Try/Catch块和一些公司特定信息被省略。上面的responseInfo对象只是一个带有一些属性的模型，用于从该方法收集信息，因此我们可以记录事件。

我怀疑问题可能在哪里，是在PostAsJsonAsync命令下面的代码。但我不知道该在那里做什么。谢谢你的帮助。

using (HttpClient httpClient = new HttpClient())
{
    // ...
    HttpResponseMessage responseMessage = await httpClient.PostAsJsonAsync(access.EndpointDirectory, stringContent).ConfigureAwait(false);
    // ...
    string responseBody = await responseMessage.Content.ReadAsStringAsync().ConfigureAwait(false);
    // ...
}