C# P / Invoke с вариантами

Вариант - это объект.

Type Conversions

During marshaling one of the most important steps is converting unmanaged types to managed types and vice versa.The CLR marshaling service knows how to perform many of these conversions for you, but you must still know how the various types match up to each other when converting the unmanaged signature to the managed function. You can use this conversion table to match up the various types.

Table 1

+-------------------------+------------------+  
|    Windows Data Type    |  .NET Data Type  |  
+-------------------------+------------------+  
| VARIANT                 |  Object          |  
+-------------------------+------------------+  

Из документации, скачанной отсюда (стр. 9 249): http://msdn.microsoft.com/en-us/library/aa719104(VS.71).aspx