无法从 system.threding.Tasks .task<byte[]> 转换为 byte[]

Question

我是 c# 的新手并且有反应。我正在使用以下方法将图像 url 转换为字节

return Convert.ToBase64String(bytes);

但我收到一条错误消息

cannot convert from System.Threading.Tasks.Task<byte[]> to byte[]

这是方法：

[HttpGet]      
[Route("GetImages")]
public  IHttpActionResult GetImages()
{    
    ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;
    WebProxy myproxy = new WebProxy("corpproxy1.tatasteel.com", 80);
        myproxy.BypassProxyOnLocal = false;
    //myproxy.UseDefaultCredentials = true;    

    HttpClientHandler handler = new HttpClientHandler()
    {
        Proxy = myproxy
    };

    using (var client = new HttpClient(handler))
    {
        var bytes = 
             client.GetByteArrayAsync("https://firebasestorage.googleapis.com/v0/b/tsl-coil- 
        qlty-monitoring-dev.appspot.com/o/1a60ce3b-eddf-4e72-b2af-b6e99873e926? 
        alt=media&token=61399a02-1009-4bb9-ad89-d1235df900e4");
           
        return Convert.ToBase64String(bytes);
    }    
}

如何更正此错误？

Answer 1

GetByteArrayAsync 是一个异步方法，return 是一个任务。您需要等待任务才能获取 return 值。为了等待它，动作方法必须是异步的。

[HttpGet]
[Route("GetImages")]
public async Task<IHttpActionResult> GetImages()
{
    ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;
    WebProxy myproxy = new WebProxy("corpproxy1.tatasteel.com", 80);
    myproxy.BypassProxyOnLocal = false;
    HttpClientHandler handler = new HttpClientHandler()
    {
        Proxy = myproxy
    };
    using (var client = new HttpClient(handler))
    {
        var bytes = await client.GetByteArrayAsync("https://firebasestorage.googleapis.com/v0/b/tsl-coil- 
             qlty-monitoring-dev.appspot.com/o/1a60ce3b-eddf-4e72-b2af-b6e99873e926? 
             alt=media&token=61399a02-1009-4bb9-ad89-d1235df900e4");
           
        return Convert.ToBase64String(bytes);
    }
}

Answer 2

由于 GetByteArrayAsync returns 任务，您必须等待任务完成：

var bytes = client.GetByteArrayAsync("https://firebasestorage.googleapis.com/v0/b/tsl-coil- 
    qlty-monitoring-dev.appspot.com/o/1a60ce3b-eddf-4e72-b2af-b6e99873e926? 
    alt=media&token=61399a02-1009-4bb9-ad89-d1235df900e4").Result

或

var bytes = await client.GetByteArrayAsync("https://firebasestorage.googleapis.com/v0/b/tsl-coil- 
    qlty-monitoring-dev.appspot.com/o/1a60ce3b-eddf-4e72-b2af-b6e99873e926? 
    alt=media&token=61399a02-1009-4bb9-ad89-d1235df900e4")

第二种方式通常比第一种好，它不会阻塞线程

无法从 system.threding.Tasks .task<byte[]> 转换为 byte[]

cannot convert from system.threding.Tasks .task<byte[]> to byte[]

c#

image-processing

task