c# - Adding Count of Arrays Together returns 0 -


i have following class, arrays populated

public class internaltag_relatedobjectsviewmodel {     public guid[] branchids { get; set; }     public guid[] companyids { get; set; }     public guid[] contactids { get; set; }     public guid[] divisionids { get; set; }     public guid[] tenderids { get; set; }     public guid[] projectids { get; set; }     public guid[] documentids { get; set; }     public guid[] newsids { get; set; }     public guid[] photosids { get; set; }              public int total     {                 {                                            return (this.branchids?.count() ?? 0 + this.companyids?.count() ?? 0 + this.contactids?.count() ?? 0 + this.divisionids?.count() ?? 0 + this.tenderids?.count() ?? 0 + this.projectids?.count() ?? 0 + this.documentids?.count() ?? 0 + this.newsids?.count() ?? 0 + this.photosids?.count() ?? 0);                         }     } }

the class populated , returned following method, on class

    static void main(string[] args)     {         internaltag_relatedobjectsviewmodel test = new internaltag_relatedobjectsviewmodel()         {             companyids = new guid[] { guid.newguid() },             newsids = new guid[] { guid.newguid(), guid.newguid() }         };          console.write(test.total);     }

but total returns 0, when of arrays have data. missing something?

you're missing precedence, basically.

it's easier see what's going on when reduced minimal example:

using system;  public class program {     public static void main()     {         string[] = { "x", "y" };         string[] b = { "x" };          int first = a?.length ?? 0 + b?.length ?? 0;         int second = (a?.length ?? 0) + (b?.length ?? 0);         console.writeline(first);   // prints 2         console.writeline(second);  // prints 3     } }

obviously 3 right answer here. what's going on?

the ?? operator has lower precedence +, first here equivalent to:

int first = ((a?.length ?? (0 + b?.length)) ?? 0;

to split up:

int? step1 = a?.length;                // 2 int? step2 = step1 ?? (0 + b?.length); // 2 int first = step2 ?? 0;

note how because result of step1 non-null, never end taking length of b.

you want apply ?? operator on result of each nullable length expression, brackets around (a?.length ?? 0) want.


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