What does param means in c# (not params)

Question

I found the following attribute declaration.

     [param: MarshalAs(UnmanagedType.LPTStr)]

what param keyword means in this context and why should we use it ?

Answer 1

param is the Attribute Target. Quote from MSDN:

The list of possible target values is shown in the following table.

 C#            Visual Basic    Applies to


 assembly      Assembly        Entire assembly
 module        Module          Current assembly module (which is different from a
                                 Visual Basic Module)
 field         Not supported   Field in a class or a struct
 event         Not supported   Event
 method        Not supported   Method or get and set property accessors
 param         Not supported   Method parameters or set property accessor parameters
 property      Not supported   Property 
 return        Not supported   Return value of a method, property indexer, or
                                 get property accessor
 type          Not supported   Struct, class, interface, enum, or delegate

In your example, the attribute is probably used for a property setter and assigns the attribute to the (implicit) value parameter.