问题描述：
在用非.NET客户端调用WebService中，按照使用Soap Toolkit中的指导实现起来很简单，但在实际使用过程中却发现一个问题。
假如Webservice提供的方法是：int SimpleMath.Add(int n1,int n2)，返回值是n1+n2, 但按照soap toolkit提供的例子，使用VC进行调用，得到的返回值却是0。

记录下我的解决过程，备忘。

试验环境：
OS:WindowsXP Professional
WebService：VS.NET 2003
WebService运行环境：IIS
客户端：VC6.0，VS.NET中的VC
SoapToolkit SDK：3.0

问题再现：
看Toolkit中稍微修改一下之后的例子代码：

#include <stdio.h>
#import "msxml4.dll"
using namespace MSXML2;
#import "C:\Program Files\Common Files\MSSoap\Binaries\mssoap30.dll" \
            exclude("IStream", "IErrorInfo", "ISequentialStream", "_LARGE_INTEGER", \
                    "_ULARGE_INTEGER", "tagSTATSTG", "_FILETIME")
using namespace MSSOAPLib30;

int test2()
{

 ISoapSerializerPtr Serializer;
 ISoapReaderPtr Reader;
 ISoapConnectorPtr Connector;
 
 // Connect to the service
 Connector.CreateInstance(__uuidof(HttpConnector));
 

 Connector->Property["EndPointURL"] = "http://localhost/WSTest/SimpleMath.asmx?WSDL";
 Connector->Connect();
 
 // Begin message
 Connector->Property["SoapAction"] = "http://tempuri.org/Add";
 Connector->BeginMessage();
 
 // Create the SoapSerializer
 Serializer.CreateInstance(__uuidof(SoapSerializer));
 
 // Connect the serializer to the input stream of the connector
 Serializer->Init(_variant_t((IUnknown*)Connector->InputStream));
 
 // Build the SOAP Message
 Serializer->startEnvelope("","","");
 Serializer->startBody("");
 Serializer->startElement("Add","http://tempuri.org/","","");
 Serializer->startElement("n1","","","");
 Serializer->writeString("5");
 Serializer->endElement();
 Serializer->startElement("n2","","","");
 Serializer->writeString("10");
 Serializer->endElement();
 Serializer->endElement();
 Serializer->endBody();
 Serializer->endEnvelope();
 
 // Send the message to the web service
 Connector->EndMessage();     
 
 // Let us read the response
 Reader.CreateInstance(__uuidof(SoapReader));
 
 // Connect the reader to the output stream of the connector
 Reader->Load(_variant_t((IUnknown*)Connector->OutputStream), "");
 
 // Display the result
 printf("Answer: %s\n", (const char*)Reader->RPCResult->text);
 return 0;
}

分析过程：

用soap toolkit的跟踪工具MSSoapT看一下，客户端到底向WebService发送了什么数据：

<SOAP-ENV:Envelope SOAP-ENV:encodingStyle="" xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/">
 <SOAP-ENV:Body SOAP-ENV:encodingStyle="">
 <SOAPSDK1:Add xmlns:SOAPSDK1="http://tempuri.org/" SOAP-ENV:encodingStyle="">
  <n1 SOAP-ENV:encodingStyle="">5</n1>
  <n2 SOAP-ENV:encodingStyle="">10</n2>
  </SOAPSDK1:Add>
  </SOAP-ENV:Body>
  </SOAP-ENV:Envelope>

再看看vs.NET调试中，IE浏览器发出的数据（模板）：

<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
  <soap:Body>
    <Add xmlns="http://tempuri.org/">
      <n1>int</n1>
      <n2>int</n2>
    </Add>
  </soap:Body>
</soap:Envelope>

区别在哪里？soaptoolkit的数据中，多了个encodingStyle属性，尽管没有制定值。我们想办法屏蔽这个属性。
在SoapSerializer30的startElement方法中的参数中按照如下方式调用，可以不制定这个属性。
改代码如下：

...
 Serializer->startElement("Add","http://tempuri.org/","NONE","");
 Serializer->startElement("n1","","NONE","");
 Serializer->writeString("5");
 Serializer->endElement();
 Serializer->startElement("n2","","NONE","");
 Serializer->writeString("10");
 Serializer->endElement();
 Serializer->endElement();
...

但返回结果还是0，看来和encodingStyle无关。看看跟踪情况：

<SOAP-ENV:Envelope SOAP-ENV:encodingStyle="" xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/">
 <SOAP-ENV:Body SOAP-ENV:encodingStyle="">
 <SOAPSDK1:Add xmlns:SOAPSDK1="http://tempuri.org/">
  <n1>5</n1>
  <n2>10</n2>
  </SOAPSDK1:Add>
  </SOAP-ENV:Body>
  </SOAP-ENV:Envelope>

问题解决：
比较一下vs.net中发出的请求，差别在哪里？认真看一下，n1和n2没有指定命名空间，那么就指定一下吧。
把代码改成：

 Serializer->startElement("Add","http://tempuri.org/","NONE","");
 Serializer->startElement("n1","http://tempuri.org/","NONE","");
 Serializer->writeString("5");
 Serializer->endElement();
 Serializer->startElement("n2","http://tempuri.org/","NONE","");
 Serializer->writeString("10");
 Serializer->endElement();
 Serializer->endElement();

测试结果正常了，返回15。

看看这时候发出的xml数据：
<SOAP-ENV:Envelope SOAP-ENV:encodingStyle="" xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/">
 <SOAP-ENV:Body SOAP-ENV:encodingStyle="">
 <SOAPSDK1:Add xmlns:SOAPSDK1="http://tempuri.org/">
  <SOAPSDK1:n1>5</SOAPSDK1:n1>
  <SOAPSDK1:n2>10</SOAPSDK1:n2>
  </SOAPSDK1:Add>
  </SOAP-ENV:Body>
  </SOAP-ENV:Envelope>

原因：

我也无法总结到底是谁的问题：（

也许是VS.NET的问题，也许是SoapToolKit的问题，也许是他提供的例子自身就有问题，也许是我的运行环境有问题，当然，更也许是我还没有真正理解xml的命名空间或没有正确使用WebService。