WCF 无法将文件作为流返回

Question

我有一个返回文件的 WCF webService 方法：

在 IMainService 中：

    [OperationContract]
    [WebInvoke(Method = "GET",
               RequestFormat = WebMessageFormat.Json,
               BodyStyle = WebMessageBodyStyle.Wrapped,
               UriTemplate = "/PerformScan")]
    Stream PerformScan();

在 MainService.cs 中：

    public Stream PerformScan()
    {
         MemoryStream SomeStream = new MemoryStream();

         // Filling this memory stream using some processes on the data

         WebOperationContext.Current.OutgoingResponse.ContentType = "image/jpeg";
         WebOperationContext.Current.OutgoingResponse.Headers.Add("Content-disposition", "inline; filename=Scan.Tiff");

         return SomeStream;      
    }

这是我的 App.Config：

<system.serviceModel>
  <services>
    <service name="ShamsScanner.WCF.ScanService" behaviorConfiguration="mexBehavior">
      <endpoint address="" binding="webHttpBinding" contract="ShamsScanner.WCF.IScanService" behaviorConfiguration="web"/>
      <host>
        <baseAddresses>
          <add baseAddress="http://localhost:1369"/>
          <add baseAddress="net.tcp://localhost:1369"/>
        </baseAddresses>
      </host>
    </service>
  </services>
  <behaviors>
    <serviceBehaviors>
      <behavior name="mexBehavior">
        <serviceMetadata httpGetEnabled="True" httpsGetEnabled="True"/>
        <serviceDebug includeExceptionDetailInFaults="False"/>
      </behavior>
    </serviceBehaviors>
    <endpointBehaviors>
      <behavior name="web">
        <webHttp/>
      </behavior>
    </endpointBehaviors>
  </behaviors>
</system.serviceModel>

当我在浏览器中调用此函数时。它不会返回任何内容。通过使用下载管理器，我会看到这个方法会不断被触发并且......什么都没有。

我已经将这个 MemoryStream 写在一个文件上，我发现它不是空的。

我应该怎么做才能返回文件？

Answer 1

感谢楼主的提示，我们需要重新定位内存流的位置。

  Stream ms = new MemoryStream();   
        FileStream fs = new FileStream(path, FileMode.Open, FileAccess.Read);
        fs.CopyTo(ms);
        ms.Position = 0;

我做了一个关于如何使用 Filestream 下载文件的演示。

IService.

[OperationContract]
    [WebGet]
    Stream Download();

Service.cs

public Stream Download()
    {
        string file = @"C:\1.png";
        try
        {
            //MemoryStream ms = new MemoryStream();
            //Stream stream = File.OpenRead(file);
            FileStream fs = new FileStream(file, FileMode.OpenOrCreate, FileAccess.Read, FileShare.Read);
            //byte[] bytes = new byte[fs.Length];
            //fs.Read(bytes, 0, (int)fs.Length);
            //ms.Write(bytes, 0, (int)fs.Length);
            WebOperationContext.Current.OutgoingResponse.ContentType = "image/png";
            WebOperationContext.Current.OutgoingResponse.Headers.Add("Content-disposition", "inline; filename=Scan.Tiff");
            return fs;
            //return Stream;
        }
        catch (Exception ex)
        {
            return null;
        }
    }

配置。

<service name="WcfServiceFile.Service1">
    <endpoint address="" binding="webHttpBinding" contract="WcfServiceFile.IService1" behaviorConfiguration="beh">
    </endpoint>
  </service>
</services>
<behaviors>
  <endpointBehaviors>
    <behavior name="beh">
      <webHttp />
    </behavior>
  </endpointBehaviors>

结果。