COM - [in] parameter as SAFEARRAY(STRUCT)

I am able to call a COM interface method using SAFEARRAY(BSTR) as input. If I define instead a simple (containing only some BSTR-s fields) STRUCT to pass into the COM I get "[System.ArgumentException] = {"The parameter is incorrect. (Exception from HRESULT: 0x80070057 (E_INVALIDARG))"

The call to my COM server is not made because as it seems the arguments from client does not match the expected arguments on server: E_INVALIDARG

Here is my declaration in IDL:

typedef enum UserEntityType
{
    User,
    Group,
    IPAddress
} UserEntityType;

[
    uuid(4786F77E-BA5F-4806-B224-12AA8601A5B1)
]
typedef struct UserEntity
{
    UserEntityType      EntityType;
    BSTR                Value;
} UserEntity;

[id(9)]          HRESULT SetUsers([in] SAFEARRAY(UserE开发者_Go百科ntity) input);

The exception is thrown at run-time when a C# 4 client calls SetUsers().

The problem was in the C# client that was using the exe COM server where

SetUsers([in] SAFEARRAY(UserEntity) input)

was defined. In order to fix this (at least for .NET 4.0) one has to change the following property of the imported COM server: Embed Interop Types = False