VICA, .NET specific error

    A custom attribute declaration is valid if and only if it
    satisfies one of the following conditions:

      1 Its creation expression is valid

      2 The actual arguments of the creation expression are
        manifest constants, or constants access.

      3 If it has some optional arguments, arguments shall be
        attributes  or  properties  of the base class  of its
        creation type.

      4 If it has some  optional  arguments, arguments  shall
	    appear only once in the list.
