如何在 C# 中转换 IDispatch

Question

我一直在用 c# 开发一个 Web 服务到 link 带有本地数据库的网站。本地应用程序的 SDK 是一个 COM 对象。第二天，我开始思考如何将下面的 VB 代码（在 SDK 协议中给出）转换为 C# 等效代码：

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

我试过这个：

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();

和

[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
            );
        }

但我收到错误

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.

请帮我看看我应该如何在 C# 中转换 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.

你的问题在这里：

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

XmlDocument 不是标准 OLE automation/dispatch 类型 。这不是：

int
float
char
BSTR
SAFEARRAY
etc

...或暴露 IDispatch 的对象，XmlDocument 未实现的 COM 接口。 XmlDocument 需要 [ComVisible] 存在。

如果对象是 COM 兼容的，那么您可以：

 comObject.SomethingOrOther(myComCompliantObject);

...没有不必要的转换。

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