如何投射IDispatch在C＃

Question

我一直在开发Web服务在C＃链接网站与本地数据库。本地应用程序的SDK是一个COM对象。我打破我的心就如何转换下面的VB代码的第二日（在SDK协议给予），以C＃相当于：

XML_DOM := CreateOleObject('MSXML2.DOMDocument.3.0') as IXMLDOMDocumen 
GetData(XML_DOM as Idispatch) 

我已经试过这样：

System.Type objType = System.Type.GetTypeFromProgID("PERCo_S20_SDK.ExchangeMain"); 
      dynamic comObject = System.Activator.CreateInstance(objType); 
      if (comObject.SetConnect("192.168.1.14", "211", "ADMIN", "") != 0) 
      { 
        //Could not connect to server! 
      } 
      XmlDocument dep_xml = new XmlDocument(); 
      XmlDeclaration dep_xml_decl = dep_xml.CreateXmlDeclaration("1.0", "UTF-8", "yes"); 
      XmlElement root = dep_xml.DocumentElement; 
      dep_xml.InsertBefore(dep_xml_decl, root); 
      XmlElement element = dep_xml.CreateElement(string.Empty, "documentrequest", string.Empty); 
      element.SetAttribute("type", "subdiv"); 
      dep_xml.AppendChild(element); 
      comObject.GetData(dep_xml as IDispatch); 
      comObject.Disconnect(); 

与

[ComImport, InterfaceType(ComInterfaceType.InterfaceIsIUnknown), Guid("00020400-0000-0000-C000-000000000046")] 
     private interface IDispatch 
     { 
      [PreserveSig] 
      int GetTypeInfoCount(out int Count); 

      [PreserveSig] 
      int GetTypeInfo 
      (
       [MarshalAs(UnmanagedType.U4)] int iTInfo, 
       [MarshalAs(UnmanagedType.U4)] int lcid, 
       out System.Runtime.InteropServices.ComTypes.ITypeInfo typeInfo 
      ); 

      [PreserveSig] 
      int GetIDsOfNames 
      (
       ref Guid riid, 
       [MarshalAs(UnmanagedType.LPArray, ArraySubType = UnmanagedType.LPWStr)] 
       string[] rgsNames, 
       int cNames, 
       int lcid, 
       [MarshalAs(UnmanagedType.LPArray)] int[] rgDispId 
      ); 

      [PreserveSig] 
      int Invoke 
      (
       int dispIdMember, 
       ref Guid riid, 
       uint lcid, 
       ushort wFlags, 
       ref System.Runtime.InteropServices.ComTypes.DISPPARAMS pDispParams, 
       out object pVarResult, 
       ref System.Runtime.InteropServices.ComTypes.EXCEPINFO pExcepInfo, 
       out UInt32 pArgErr 
      ); 
     } 

，但我得到的错误

An exception of type 'System.ArgumentException' occurred in System.Dynamic.dll but was not handled in user code 

Additional information: Could not convert argument 0 for call to GetData. 

请帮我解决一下如何在C＃中投射IDispatch。

Answer 1

An exception of type 'System.ArgumentException' occurred in System.Dynamic.dll but was not handled in user code

Additional information: Could not convert argument 0 for call to GetData.

你的问题是在这里：

XmlDocument dep_xml = ... 
comObject.GetData(dep_xml as IDispatch); // <------ BANG!! 

XmlDocument不是一个标准的OLE自动化/调度方式。这不是一个：

• int
• float
• char
• BSTR
• SAFEARRAY
• etc

...或物体暴露IDispatch，XmlDocument未实现的COM接口。 XmlDocument需要[ComVisible]出席。

如果对象是COM兼容的，那么你可以只：

comObject.SomethingOrOther(myComCompliantObject); 

...没有不必要的演员。