vb.net - How do you pass a lambda function into a regular function as a default value for a conditional argument? -

the following:

delegate function operationdelegate(byval x double) double public function test(optional byref operation operationdelegate = addressof defaultoperation) double     return operation.invoke(3) end function 

gives me error: constant expression required. addressof defaultoperation causing error using visual studio 2013.

i have tried defining defaultoperation in 2 following ways.

public function defaultoperation(byval x double) double     return x end function  dim defaultoperation operationdelegate = function(x double) double                                                 return x                                             end function 

in either case has not worked. ressource have been using: https://msdn.microsoft.com/en-us/library/bb531253.aspx

anyways time.

a similar questions found:

• https://softwareengineering.stackexchange.com/questions/304320/specifying-a-default-value-for-an-optional-anonymous-function-parameter-in-vb-ne
• lambda default argument

as suggested in comments on original post, lambda can not used optional parameter.

an alternative overload function (test, in example) version no parameters , version delegate parameter.

delegate function operationdelegate(byval x double) double  public function test() double    return test(addressof operationdelegate) end function  public function test(operation operationdelegate) double    return operation.invoke(3) end function