Nullable<T> for generic method in c#? -

how can write generic method can take nullable object use extension method. want add xelement parent element, if value used not null.

e.g.

public static xelement addoptionalelement<t>(this xelement parentelement, string childname, t childvalue){ ... code check if value null add element parent here if not null ... } 

if make addoptionalelement<t?>(...) compiler errors. if make addoptionalelement<nullable<t>>(...) compiler errors.

is there way can acheive this?

i know can make call method:

parent.addoptionalelement<mytype?>(...) 

but way?

public static xelement addoptionalelement<t>(     xelement parentelement, string childname, t? childvalue)     t : struct {     // ... }