c# - 从 OperationContract 方法返回图像(WCF 服务)

Question

我正在尝试从 WCF 服务获取 Image。

我有一个 OperationContract 函数，它返回一个 Image 给客户端，但是当我从客户端调用它时，我得到这个异常(exception):

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'.

客户:

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

服务.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(interface):

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

那么为什么会发生这种情况，我该如何解决？

Answer 1

我想通了。

• 首先使用 TransferMode.Streamed 或 StreamedResponse(取决于您的需要)。
• 返回流，不要忘记设置 Stream.Postion = 0，这样您就可以从头开始读取流。

在服务中:

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 is very important
        return ms;
    }
}

接口(interface):

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

在客户端:

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());
    }
}