从WebMethod返回SpreadsheetGear工作簿流

Question

我想提供一个Web服务，让我可以下载某些Excel工作簿。这些Excel工作簿是可以用数据修改的SpreadsheetGear对象。我不想将它们写入文件并返回文件。相反，我想将它们串流到浏览器中，以便用户获得下载的文件。

这是我尝试不工作，从this guide from SpreadsheetGear's site得出：

[System.Web.Services.WebMethod(
    Description = "Returns a stream for the excel file")] 
    public ActionResult downloadTemplate(string excelFileName) 
    { 
     var workbook = makeSpreadsheetGearWorkbookFrom(excelFileName); 
     // Save workbook to an Open XML (XLSX) workbook stream. 
     System.IO.Stream stream = workbook.SaveToStream(
      SpreadsheetGear.FileFormat.OpenXMLWorkbook); 

     // Reset stream's current position back to the beginning. 
     stream.Seek(0, System.IO.SeekOrigin.Begin); 

     return new FileStreamResult(stream, 
      "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"); 
    } 

我得到以下错误：

The web service returned the following result: 

500 - Internal Server Error 
System.InvalidOperationException: There was an error generating the XML document. ---> System.InvalidOperationException: System.Web.Mvc.FileStreamResult cannot be serialized because it does not have a parameterless constructor. 
    at System.Xml.Serialization.TypeDesc.CheckSupported() [0x0001c] in <611e64636ff745389933c69c817b2d4a>:0 
    at System.Xml.Serialization.TypeScope.GetTypeDesc (System.Type type, System.Reflection.MemberInfo source, System.Boolean directReference, System.Boolean throwOnError) [0x0006a] in <611e64636ff745389933c69c817b2d4a>:0 
    at System.Xml.Serialization.TypeScope.GetTypeDesc (System.Type type) [0x00000] in <611e64636ff745389933c69c817b2d4a>:0 
    at System.Xml.Serialization.XmlSerializationWriter.CreateUnknownTypeException (System.Type type) [0x00039] in <611e64636ff745389933c69c817b2d4a>:0 
    at System.Xml.Serialization.XmlSerializationWriter.CreateUnknownTypeException (System.Object o) [0x00007] in <611e64636ff745389933c69c817b2d4a>:0 
    at Microsoft.Xml.Serialization.GeneratedAssembly.XmlSerializationWriter1.Write3_ActionResult (System.String n, System.String ns, System.Web.Mvc.ActionResult o, System.Boolean isNullable, System.Boolean needType) [0x00048] in <3fa7e61a58e74ec08df7a46ab2fb8972>:0 
    at Microsoft.Xml.Serialization.GeneratedAssembly.XmlSerializationWriter1.Write7_ActionResult (System.Object o) [0x00028] in <3fa7e61a58e74ec08df7a46ab2fb8972>:0 
    at Microsoft.Xml.Serialization.GeneratedAssembly.ActionResultSerializer.Serialize (System.Object objectToSerialize, System.Xml.Serialization.XmlSerializationWriter writer) [0x00000] in <3fa7e61a58e74ec08df7a46ab2fb8972>:0 
    at System.Xml.Serialization.XmlSerializer.Serialize (System.Xml.XmlWriter xmlWriter, System.Object o, System.Xml.Serialization.XmlSerializerNamespaces namespaces, System.String encodingStyle, System.String id) [0x00098] in <611e64636ff745389933c69c817b2d4a>:0 
    StackTraceEnd 
    at System.Xml.Serialization.XmlSerializer.Serialize (System.Xml.XmlWriter xmlWriter, System.Object o, System.Xml.Serialization.XmlSerializerNamespaces namespaces, System.String encodingStyle, System.String id) [0x0012f] in <611e64636ff745389933c69c817b2d4a>:0 
    at System.Xml.Serialization.XmlSerializer.Serialize (System.Xml.XmlWriter xmlWriter, System.Object o, System.Xml.Serialization.XmlSerializerNamespaces namespaces, System.String encodingStyle) [0x00000] in <611e64636ff745389933c69c817b2d4a>:0 
    at System.Xml.Serialization.XmlSerializer.Serialize (System.Xml.XmlWriter xmlWriter, System.Object o, System.Xml.Serialization.XmlSerializerNamespaces namespaces) [0x00000] in <611e64636ff745389933c69c817b2d4a>:0 
    at System.Xml.Serialization.XmlSerializer.Serialize (System.IO.TextWriter textWriter, System.Object o, System.Xml.Serialization.XmlSerializerNamespaces namespaces) [0x00015] in <611e64636ff745389933c69c817b2d4a>:0 
    at System.Xml.Serialization.XmlSerializer.Serialize (System.IO.TextWriter textWriter, System.Object o) [0x00000] in <611e64636ff745389933c69c817b2d4a>:0 
    at System.Web.Services.Protocols.XmlReturnWriter.Write (System.Web.HttpResponse response, System.IO.Stream outputStream, System.Object returnValue) [0x00079] in <11189ae945ae429a8c10c5e8a65a097a>:0 
    at System.Web.Services.Protocols.HttpServerProtocol.WriteReturns (System.Object[] returnValues, System.IO.Stream outputStream) [0x0003f] in <11189ae945ae429a8c10c5e8a65a097a>:0 
    at System.Web.Services.Protocols.WebServiceHandler.WriteReturns (System.Object[] returnValues) [0x00051] in <11189ae945ae429a8c10c5e8a65a097a>:0 
    at System.Web.Services.Protocols.WebServiceHandler.Invoke() [0x000cc] in <11189ae945ae429a8c10c5e8a65a097a>:0 

我应该如何看待呢？

Answer 1

通过返回字节而不是构造StreamResult的列表，像这样问题解决了：

public byte[] downloadTemplate(string excelFileName) 
    //... 
    byte[] modelData = toByteArray(stream); 
    return modelData; 
} 

public byte[] toByteArray(System.IO.Stream stream) 
{ 
    using (System.IO.MemoryStream ms = new System.IO.MemoryStream()) 
    { 
     stream.CopyTo(ms); 
     return ms.ToArray(); 
    } 
} 

这是很容易把字节数组到JObject，然后到一个XML信封。