任务不包含内容的定义

Question

如何克服下面的错误？我已经按照下面的教程，但我得到的红线表示不包含Content的定义。 https://www.youtube.com/watch?v=IVvJX4CoLUY

private void UploadFile_Cliked(object sender, EventArgs e)
{
    var content = new MultipartFormDataContent();
    content.Add(new StreamContent(_mediaFile.GetStream()),
        "\"file\"",
        $"\"{_mediaFile.Path}\"");
    var httpClient = new HttpClient();

    var uploadServiceBaseAddress = "http://192.168.137.1/pic/";
    var httpResponseMessage = httpClient.PostAsync(uploadServiceBaseAddress, content);
    RemotePathLabel.Text = httpResponseMessage.Content.ReadAsStringAsync();
}

'Task'不包含'Content'的定义，也没有扩展方法'Content'可以找到接受'Task'类型的第一个参数（你是否缺少using指令或汇编引用？）

这是错误，但任何想法解决它？

我已添加此Microsoft.AspNet.WebApi.Client包但仍然失败

Answer 1

使事件处理程序异步，然后等待返回Task派生结果的函数，因为在调用ReadAsStringAsync时你会遇到同样的问题

private HttpClient httpClient = new HttpClient();

private async void UploadFile_Cliked(object sender, EventArgs e) {
    var content = new MultipartFormDataContent();
    content.Add(new StreamContent(_mediaFile.GetStream()),
        "\"file\"",
        $"\"{_mediaFile.Path}\"");        

    var uploadServiceBaseAddress = "http://192.168.137.1/pic/";
    var httpResponseMessage = await httpClient.PostAsync(uploadServiceBaseAddress, content);
    RemotePathLabel.Text = await httpResponseMessage.Content.ReadAsStringAsync();
}

请注意，事件处理程序是允许使用async void的规则的例外

参考Async/Await - Best Practices in Asynchronous Programming