返回圖像（WCF服務）

Question

林試圖從WCF服務的圖片
我有一個返回的圖片給客戶端，
但是當我從客戶 調用它，我得到這個異常的OperationContract的功能： The socket connection was aborted. This could be caused by an error processing your message or a receive timeout being exceeded by the remote host, or an underlying network resource issue. Local socket timeout was '00:00:59.9619978'.

客戶：

private void btnNew_Click(object sender, EventArgs e) 
    { 
     picBox.Picture = client.GetScreenShot(); 
    } 

Service.cs：

public Image GetScreenShot() 
    { 
     Rectangle bounds = Screen.GetBounds(Point.Empty); 
     using (Bitmap bmp = new Bitmap(bounds.Width,bounds.Height)) 
     { 
      using (Graphics g = Graphics.FromImage(bmp)) 
      { 
       g.CopyFromScreen(Point.Empty, Point.Empty, bounds.Size); 
      } 
      using (MemoryStream ms = new MemoryStream()) 
      { 
       bmp.Save(ms, System.Drawing.Imaging.ImageFormat.Png); 
       return Image.FromStream(ms); 
      } 
     } 
    } 

IScreenShot接口：

[ServiceContract] 
public interface IScreenShot 
{ 
    [OperationContract] 
    System.Drawing.Image GetScreenShot(); 
} 

所以這是爲什麼發生，如何解決呢？

Answer 1

我已經想通了。

• 首先使用TransferMode.Streamed //或StreamedResponse取決於您的需要。
• 返回流，並且不要忘記設置Stream.Postion = 0所以開始從開始讀取流。

在服務

：

public Stream GetStream() 
    { 
     Rectangle bounds = Screen.GetBounds(Point.Empty); 
     using (Bitmap bmp = new Bitmap(bounds.Width, bounds.Height)) 
     { 
      using (Graphics g = Graphics.FromImage(bmp)) 
      { 
       g.CopyFromScreen(Point.Empty, Point.Empty, bounds.Size); 
      } 
      MemoryStream ms = new MemoryStream(); 
      bmp.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg); 
      ms.Position = 0; //This's a very important 
      return ms; 
     } 
    } 

接口：

[ServiceContract] 
public interface IScreenShot 
{ 
    [OperationContract] 
    Stream GetStream(); 
} 

在客戶端：

public partial class ScreenImage : Form 
{ 
    ScreenShotClient client; 
    public ScreenImage(string baseAddress) 
    { 
     InitializeComponent(); 
     NetTcpBinding binding = new NetTcpBinding(SecurityMode.None); 
     binding.TransferMode = TransferMode.StreamedResponse; 
     binding.MaxReceivedMessageSize = 1024 * 1024 * 2; 
     client = new ScreenShotClient(binding, new EndpointAddress(baseAddress)); 
    } 

    private void btnNew_Click(object sender, EventArgs e) 
    { 
     picBox.Image = Image.FromStream(client.GetStream()); 
    } 
} 

Answer 2

您將需要定義可序列化的內容。 System.Drawing.Image是，但默認情況下不在WCF的cotnext（使用DataContractSerializer）中。這可能包括將原始字節作爲數組返回，或者將序列化返回爲字符串（base64，JSON）或實現可序列化的DataContract，並且可以攜帶數據。

正如其他人所說，WCF支持流式傳輸，但這不是問題的關鍵。根據數據的大小，您可能希望這樣做，並且這樣做會減少問題本身，因爲您將流式傳輸字節（來自明顯的頂級視圖）。

您也可以take a look at this answer來幫助您獲得實際的異常詳細信息，例如完整的堆棧跟蹤，而不僅僅是故障信息。

Answer 3

您可以使用Stream來返回大量數據/圖像。

Sample Example(returning Image as Stream) from MSDN