vb.net - How do I sum an array of structures? -

i creating arrays of structures defined, when stripped essentials purpose of question, this:-

public structure mystruct      public innards double      public shared operator +(byval example1 mystruct, byval example2 mystruct) mystruct         dim out_struct mystruct         out_struct.innards = example1.innards + example2.innards         return out_struct     end operator  end structure 

i set array:-

dim my_struct1 mystruct dim my_struct2 mystruct dim my_struct3 mystruct  my_struct1.innards = 1 my_struct2.innards = 2 my_struct3.innards = 3  dim my_struct_array() mystruct = {my_struct1, my_struct2, my_struct3} 

and want calculate sum of elements in array:-

dim my_total mystruct my_total = my_struct_array.sum 

but results in compilation error:-

overload resolution failed because no accessible 'sum' accepts number of arguments.

is there way work? interface have implement? or have resort linq?

arrays don't have sum function can use linq; however, linq not see + operator works on predefined numeric types.

dim my_total double my_total = my_struct_array.sum(function(x) x.innards) 

your + operator works if work mystructs explicitly:

dim t mystruct = my_struct1 + my_struct2 

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you define shared sum function or extension method. here sum function

public shared function sum(items ienumerable(of mystruct)) mystruct     dim total double      each x in items         total += x.innards     next     dim t new mystruct     t.innards = total     return t end function 

and call this:

t = mystruct.sum(my_struct_array) 

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as extension method:

public module myextensions     <extension()>     public function sum(items ienumerable(of mystruct)) mystruct         dim total double          each x in items             total += x.innards         next         dim t new mystruct         t.innards = total         return t     end function end module 

then can intended first:

t = my_struct_array.sum() 

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one more thing: structs should immutable. reason copy of structs, not references, when access struct values in collections. if this:

my_struct_list(2).innards = 100 

... not expected result! list indexer returns copy of struct within list, , change innards field of copy, struct in list not changed!

therefore create struct this:

public structure mystruct     private readonly m_value double      public sub new (value double)         m_value = value     end sub      public readonly property value() double                     return m_value         end     end property      public shared operator +(byval x mystruct, byval y mystruct) mystruct         return new mystruct(x.m_value + y.m_value)     end operator end structure 

this struct immutable. cannot change value once has been initialized new(initialvalue). if want change value within list, need this:

my_struct_list(2) = new mystruct(100) 

this behave expected.