这种情况下，VARIANT变量的vt值是多少，哪个成员是有效的？

[Tiger-3D]

VC写的OCX，其中一个接口的参数为指针类型，为了供多种语言调用，OCX中将其定义成了VARIANT&类型。
C#调用这个OCX，传递了一个非托管内存的指针

经过测试，OCX接收到这个参数之后，VARIANT&参数的vt的值是22，并且VARIANT&参数的plVal和llVal的值都能够成功转化为自定义的结构体。

现在，请问，这是怎么个原理，为什么vt的值是22，为什么plVal和llVal的值都能转化呢？

[yaozhiyong110]

因为里面其实就是一个union

[okvee]

vt 对应类型，比如 VT_INT 这个就是22 XXval 对应的值 不晓得对不对，反正我是这么用的

[珍惜生命远离CPP]

typedef struct tagVARIANT VARIANT;
typedef struct tagVARIANT VARIANTARG;
struct tagVARIANT
    {
    union 
        {
        struct __tagVARIANT
            {
            VARTYPE vt;
            WORD wReserved1;
            WORD wReserved2;
            WORD wReserved3;
            union 
                {
                LONGLONG llVal;
                LONG lVal;
                BYTE bVal;
                SHORT iVal;
                FLOAT fltVal;
                DOUBLE dblVal;
                VARIANT_BOOL boolVal;
                _VARIANT_BOOL bool;
                SCODE scode;
                CY cyVal;
                DATE date;
                BSTR bstrVal;
                IUnknown *punkVal;
                IDispatch *pdispVal;
                SAFEARRAY *parray;
                BYTE *pbVal;
                SHORT *piVal;
                LONG *plVal;
                LONGLONG *pllVal;
                FLOAT *pfltVal;
                DOUBLE *pdblVal;
                VARIANT_BOOL *pboolVal;
                _VARIANT_BOOL *pbool;
                SCODE *pscode;
                CY *pcyVal;
                DATE *pdate;
                BSTR *pbstrVal;
                IUnknown **ppunkVal;
                IDispatch **ppdispVal;
                SAFEARRAY **pparray;
                VARIANT *pvarVal;
                PVOID byref;
                CHAR cVal;
                USHORT uiVal;
                ULONG ulVal;
                ULONGLONG ullVal;
                INT intVal;
                UINT uintVal;
                DECIMAL *pdecVal;
                CHAR *pcVal;
                USHORT *puiVal;
                ULONG *pulVal;
                ULONGLONG *pullVal;
                INT *pintVal;
                UINT *puintVal;
                struct __tagBRECORD
                    {
                    PVOID pvRecord;
                    IRecordInfo *pRecInfo;
                    }    __VARIANT_NAME_4;
                }    __VARIANT_NAME_3;
            }    __VARIANT_NAME_2;
        DECIMAL decVal;
        }    __VARIANT_NAME_1;
struct tagVARIANT  
   {
    union 
       {
       struct __tagVARIANT
       {
          VARTYPE vt;
          WORD wReserved1;
          WORD wReserved2;
          WORD wReserved3;
   union {
      LONGLONG                llval;             // VT_I8. 
      LONG                    lVal;              // VT_I4.
      BYTE                    bVal;              // VT_UI1.
      SHORT                   iVal;              // VT_I2.
      FLOAT                   fltVal;            // VT_R4.
      DOUBLE                  dblVal;            // VT_R8.
      VARIANT_BOOL            boolVal;           // VT_BOOL.
      _VARIANT_BOOL           bool;
      SCODE                   scode;             // VT_ERROR.
      CY                      cyVal;             // VT_CY.
      DATE                    date;              // VT_DATE.
      BSTR                    bstrVal;           // VT_BSTR.
      IUnknown                * punkVal;         // VT_UNKNOWN.
      IDispatch               * pdispVal;        // VT_DISPATCH.
      SAFEARRAY               * parray;          // VT_ARRAY|*.
      BYTE                    * pbVal;           // VT_BYREF|VT_UI1.
      SHORT                   * piVal;           // VT_BYREF|VT_I2.
      LONG                    * plVal;           // VT_BYREF|VT_I4.
      LONGLONG                * pllVal;          // VT_BYREF|VT_I8.
      FLOAT                   * pfltVal;         // VT_BYREF|VT_R4.
      DOUBLE                  * pdblVal;         // VT_BYREF|VT_R8.
      VARIANT_BOOL            * pboolVal;        // VT_BYREF|VT_BOOL.
      _VARIANT_BOOL           * pbool;
      SCODE                   * pscode;          // VT_BYREF|VT_ERROR.
      CY                      * pcyVal;          // VT_BYREF|VT_CY.
      DATE                    * pdate;           // VT_BYREF|VT_DATE.
      BSTR                    * pbstrVal;        // VT_BYREF|VT_BSTR.
      IUnknown                ** ppunkVal;       // VT_BYREF|VT_UNKNOWN.
      IDispatch               ** ppdispVal;      // VT_BYREF|VT_DISPATCH.
      SAFEARRAY               ** pparray;        // VT_BYREF|VT_ARRAY.
      VARIANT                 * pvarVal;         // VT_BYREF|VT_VARIANT.
      PVOID                   * byref;           // Generic ByRef.
      CHAR                    cVal;              // VT_I1.
      USHORT                  uiVal;             // VT_UI2.
      ULONG                   ulVal;             // VT_UI4.
      ULONGLONG               ullVal;            // VT_UI8.
      INT                     intVal;            // VT_INT.
      UINT                    uintVal;           // VT_UINT.
      DECIMAL                 * pdecVal          // VT_BYREF|VT_DECIMAL.
      CHAR                    * pcVal;           // VT_BYREF|VT_I1.
      USHORT                  * puiVal;          // VT_BYREF|VT_UI2.
      ULONG                   * pulVal;          // VT_BYREF|VT_UI4.
      ULONGLONG               * pullVal;         // VT_BYREF|VT_UI8.
      INT                     * pintVal;         // VT_BYREF|VT_INT.
      UINT                    * puintVal;        // VT_BYREF|VT_UINT.
      struct __tagBRECORD
      {
      PVOID                   pvRecord;
      IRecordInfo             *pRecInfo;
      }    __VARIANT_NAME_4;
   }    __VARIANT_NAME_3;
  }    __VARIANT_NAME_2;
  DECIMAL decVal;
}    __VARIANT_NAME_1;

   };
};
 

[oyljerry]

union，但是最好能用对应类型的变量数据