c# - Linq to objects: if number is in dictionary, return number, else return 0 -

i have dictionary<int int>. when check keys of dictionary number , in it, want return number, else want linq query return 0.

something following, except working

var t = (from result in results          result.key == 3          select result.key != null ? result.value : 0).first(); 

because problem when there no number in list, sequence contains no element, can't check null or count.

just use trygetvalue.

int i; results.trygetvalue(3, out i); 

if finds it, i set value. if not, i default, 0 int.

if want value besides default, can this:

int i; if (!results.trygetvalue(3, out i)) {     = 5; // or whatever other value want; } 

and if you, me, hate out parameter style, can create extension method

public static class idictionaryextensions {     public static tvalue getvalueordefault<tkey, tvalue>(this idictionary<tkey, tvalue> dictionary, tkey key)     {         t i;         dictionary.trygetvalue(key, out i);         return i;     } } 

and can call:

int = dictionary.getvalueordefault(3); 

and if want fancier can create oveload of extension:

    public static tvalue getvalueordefault<tkey, tvalue>(this idictionary<tkey, tvalue> dictionary, tkey key, tvalue defaultvalue)     {         t i;         return dictionary.trygetvalue(key, out i) ? : defaultvalue;     } 

which can called

int = dictionary.getvalueordefault(3, 5);