[英]How do I call a VB6 COM object from C# with dynamic when it has a ref parameter?
我有以下想要从C#调用的旧版VB6函数。
Public Function CreateMiscRepayment(ByRef objMiscRepayment As MiscRepayment) As Variant
' Code that sets objMiscRepayment here
End Function
我在C#中使用以下代码,但出现异常:
dynamic vb6ComObject = Activator.CreateInstance(Type.GetTypeFromProgID(progId));
dynamic miscRepayment = null;
dynamic result = vb6ComObject.CreateMiscRepayment(ref miscRepayment);
例外是:
System.ArgumentException: Could not convert argument 0 for call to CreateMiscRepayment.
at System.Dynamic.ComRuntimeHelpers.CheckThrowException(Int32 hresult, ExcepInfo& excepInfo, UInt32 argErr, String message)
at CallSite.Target(Closure , CallSite , ComObject , Object& )
at CallSite.Target(Closure , CallSite , ComObject , Object& )
at CallSite.Target(Closure , CallSite , Object , Object& )
at CallSite.Target(Closure , CallSite , Object , Object& )
Application\ApplicationClasses.cs(65,0): at ApplicationClasses.CanInstantiateMiscRepayment()
我试过将ref
更改为out
但得到相同的错误。 如果我省略ref
,则该方法执行时没有错误,但是miscRepayment
当然仍然为空,而不是包含应该传递的对象。
我尝试了其他方法,包括使用VB.NET(因为它一直比C#对COM更友好)。
使用以下VB.NET代码:
Dim vb6ComObject = Activator.CreateInstance(System.Type.GetTypeFromProgID(progId))
Dim miscRepayment = Nothing
Dim result = vb6ComObject.CreateMiscRepayment(miscRepayment)
它引发以下类似但不同的异常:
System.Runtime.InteropServices.COMException: Type mismatch. (Exception from HRESULT: 0x80020005 (DISP_E_TYPEMISMATCH))
at Microsoft.VisualBasic.CompilerServices.LateBinding.LateGet(Object o, Type objType, String name, Object[] args, String[] paramnames, Boolean[] CopyBack)
at Microsoft.VisualBasic.CompilerServices.NewLateBinding.LateGet(Object Instance, Type Type, String MemberName, Object[] Arguments, String[] ArgumentNames, Type[] TypeArguments, Boolean[] CopyBack)
UnitTest1.vb(19,0): at TestProject1.UnitTest1.TestMethod1()
有趣的是,如果我将C#或VB.NET示例代码中的调用更改为使用null
/ Nothing
而不是miscRepayment
则代码将执行而不会引发异常。 我什至在VB6 COM对象的代码中设置了一个断点,并可以确认代码已在那一端正确执行。 显然,通过将miscRepayment
参数设置为null
/ Nothing
,.NET中将无法接收创建的对象。 问题必须与参数的编组有关。
我还尝试过将Type.InvokeMember
与ParameterModifier
参数一起使用,该ParameterModifier
将miscRepayment
标记为ref
参数,但得到以下异常:
System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.Runtime.InteropServices.COMException: Type mismatch. (Exception from HRESULT: 0x80020005 (DISP_E_TYPEMISMATCH))
--- End of inner exception stack trace ---
at System.RuntimeType.InvokeDispMethod(String name, BindingFlags invokeAttr, Object target, Object[] args, Boolean[] byrefModifiers, Int32 culture, String[] namedParameters)
at System.RuntimeType.InvokeMember(String name, BindingFlags bindingFlags, Binder binder, Object target, Object[] providedArgs, ParameterModifier[] modifiers, CultureInfo culture, String[] namedParams)
UnitTest1.vb(18,0): at TestProject1.UnitTest1.TestMethod1()
最后,我尝试了以下VB.NET代码:
Dim vb6ComObject = Activator.CreateInstance(System.Type.GetTypeFromProgID(progId))
Dim args(0) As Object
Microsoft.VisualBasic.CompilerServices.LateBinding.LateCall(vb6ComObject, type, "CreateMiscRepayment", args, Nothing, New Boolean() {True})
它引发以下异常:
System.Runtime.InteropServices.COMException: Type mismatch. (Exception from HRESULT: 0x80020005 (DISP_E_TYPEMISMATCH))
at Microsoft.VisualBasic.CompilerServices.LateBinding.InternalLateCall(Object o, Type objType, String name, Object[] args, String[] paramnames, Boolean[] CopyBack, Boolean IgnoreReturn)
at Microsoft.VisualBasic.CompilerServices.LateBinding.LateCall(Object o, Type objType, String name, Object[] args, String[] paramnames, Boolean[] CopyBack)
UnitTest1.vb(17,0): at TestProject1.UnitTest1.TestMethod1()
对于所有引发异常的代码,都不会调用VB6 COM对象。 尝试编组ref
参数时,COM互操作代码必须处于阻塞状态。
在我的Google搜索中,我遇到了一些使用Type.InvokeMember
示例,但是ref
参数始终用于简单类型,例如整数和字符串。
实际上不是答案,而是一种解决方法。
在我看来,当您将访问COM对象的方式从dynamic
更改为静态时,问题就消失了。 通过静态方式,我的意思是使用C:\\Program Files (x86)\\Microsoft SDKs\\Windows\\v7.0A\\Bin\\TlbImp.exe
为COM对象准备一个dll。 我想这是早期约束力。
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