Default value to a optional class variable parameter function call in vb.net -

i trying pass class variable optional parameter function. requires default value. set default value optional class variable.

private function savefruit(optional byval tempbanana bananaclass = ?) 

reference types' default value nothing (the null reference).

private function savefruit(optional byval tempbanana bananaclass = nothing)     if tempbanana nothing tempbanana = otherdefaultbanana     ..... end function 

as shown in example above have check if it's nothing is-operator before can use it, otherwise nullreferenceexception. can either assign instance exists or 1 initialize now.