将COM接口传递回库的正确方法是什么？

当试图将接口作为参数从.NET传递到DLL时，我得到一个System.InvalidCastException运行时错误。代码在.NET方面失败了，从来没有交给Delphi方面。将COM接口传递回库的正确方法是什么？

在Delphi中构建一个简单的ActiveX库dll。两个自动化对象：MyContent和MyContainer。 MyContainer具有单一方法Add，其需要由IMyContent继承的IBase接口。 IBase是IDispatch

[ 
    uuid(E29018FF-F142-4BAE-B7A4-AE0A8847E930), 
    version(1.0) 

] 
library DelphiComLib 
{ 

    importlib("stdole2.tlb"); 

    interface IMyBase; 
    interface IMyContainer; 
    coclass MyContainer; 
    interface IMyContent; 
    coclass MyContent; 


    [ 
    uuid(07D17021-9E7F-4D7A-B861-59A35EC686A0), 
    dual, 
    oleautomation 
    ] 
    interface IMyBase: IDispatch 
    { 
    }; 

    [ 
    uuid(A6AB6F7D-8BEB-459F-A2F8-BC06FF81A45D), 
    helpstring("Dispatch interface for MyContainer Object"), 
    dual, 
    oleautomation 
    ] 
    interface IMyContainer: IDispatch 
    { 
    [id(0x000000C9)] 
    HRESULT _stdcall Add([in] IMyBase* AMyBase); 
    }; 

    [ 
    uuid(AB82964C-13D7-423B-9B16-A789D5D30421), 
    helpstring("Dispatch interface for MyContent Object"), 
    dual, 
    oleautomation 
    ] 
    interface IMyContent: IMyBase 
    { 
    }; 

    [ 
    uuid(DDDF77E5-E6A6-4429-BD4A-D9695E9E6CED), 
    helpstring("MyContainer Object") 
    ] 
    coclass MyContainer 
    { 
    [default] interface IMyContainer; 
    }; 

    [ 
    uuid(134BF8B2-30C3-4C37-8F74-3F677808300A), 
    helpstring("MyContent Object") 
    ] 
    coclass MyContent 
    { 
    [default] interface IMyContent; 
    }; 

};

类的实现并不重要。为了保持最小的样本，Add的实现可以留空。这里是集装箱

unit Unit1; 

{$WARN SYMBOL_PLATFORM OFF} 

interface 

uses 
    ComObj, ActiveX, DelphiComLib_TLB, StdVcl; 

type 
    TMyContainer = class(TAutoObject, IMyContainer) 
    protected 
    procedure Add(const AMyBase: IMyBase); safecall; 

    end; 

implementation 

uses ComServ; 

procedure TMyContainer.Add(const AMyBase: IMyBase); 
begin 

end; 

initialization 
    TAutoObjectFactory.Create(ComServer, TMyContainer, Class_MyContainer, 
    ciMultiInstance, tmApartment); 
end.

...和内容

unit Unit2; 

{$WARN SYMBOL_PLATFORM OFF} 

interface 

uses 
    ComObj, ActiveX, DelphiComLib_TLB, StdVcl; 

type 
    TMyContent = class(TAutoObject, IMyContent) 
    protected 

    end; 

implementation 

uses ComServ; 

initialization 
    TAutoObjectFactory.Create(ComServer, TMyContent, Class_MyContent, 
    ciMultiInstance, tmApartment); 
end.

注册库并添加引用到一个控制台应用程序。如果我在实现IBase我可以通过接口回成功.NET创建一个类，下面的代码将产生运行时错误

using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Text; 
using System.Threading.Tasks; 
using DelphiComLib; 
namespace ConsoleApplication2 
{ 
    class Program 
    { 
     static void Main(string[] args) 
     { 
      IMyContainer container = new MyContainer(); 
      IMyContent content = new MyContent(); 
      container.Add(content); 


     } 
    } 
}

。

这里是.NET

堆栈跟踪

at System.StubHelpers.InterfaceMarshaler.ConvertToNative(Object objSrc, IntPtr itfMT, IntPtr classMT, Int32 flags) 
    at DelphiComLib.IMyContainer.Add(IMyBase AMyBase) 
    at ConsoleApplication2.Program.Main(String[] args) in c:\users\jaspers\documents\visual studio 2015\Projects\ConsoleApplication2\ConsoleApplication2\Program.cs:line 15 
    at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args) 
    at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args) 
    at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly() 
    at System.Threading.ThreadHelper.ThreadStart_Context(Object state) 
    at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx) 
    at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx) 
    at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) 
    at System.Threading.ThreadHelper.ThreadStart()

来源

2016-09-13 Jasper Schellingerhout

您的问题无关的接口是如何传递到您的COM DLL。

错误System.InvalidCastException仅仅是因为从Delphi实现端投射IMyContent到IMyBase失败。原因是严格地说你的实现并不直接实现IMyBase接口（尽管它实现了派生的IMyContent接口）。你可以尝试一下：

var 
    MyContent: IMyContent; 
    MyBase: IMyBase; 
begin 
    MyContent := CoMyContent.Create; 
    MyBase := MyContent as IMyBase; // EIntfCastError is raised 
end;

你的实现类必须实现IMyBase明确的铸造工作：

这将改变你的实现类的声明：

type 
    TMyContent = class(TAutoObject, IMyContent, IMyBase) 
    ... 
    end;

这反过来将使任何COM clie的铸造工作nt代码（Delphi，C++，.NET等）

来源

2016-09-14 05:54:26

将COM接口传递回库的正确方法是什么？

回答

相关问题