c# - Can you use variables in their own initialization line (tryGetOrElse in a dictionary)? -

consider following code:

private dictionary<robotsettings, trader> createtradersfor(ienumerable<robotsettings> settings) {     var traderset = new dictionary<tuple<igateway, ibroker>, trader>();      return settings.todictionary(s => s, s =>     {         var key = tuple.create(s.gateway, s.broker);          trader trader = traderset.trygetvalue(key, out trader)             ? trader             : traderset[key] = new trader(s.gateway, s.broker);         return trader;     }); } 

i'm talking initialization of trader variable in closure, uses in same line being instantiated.

i've been using pattern of dealing dictionaries lot lately, cause don't uninitialized variables :) , know if guaranteed compile in future.

beside looking odd, there nothing wrong - technically.
first, declaration of trader executed, there exists trader object without value assigned. second, trygetvalue part evaluated , returns either true or false. if returned true, assigned trader returned. if returns false, new trader created , added dictionary via assignment operation. result of assignment operation value of object assigned to. new trader. third, result of ternary operator returned , assigned trader.

it unlikely change in future, because changing order of evaluation of statement breaking change.

update:
because looks odd, not use it. solve problem creating extension method idictionary<tkey, tvalue> called getoradd.
so:

public static tvalue getoradd<tkey, tvalue>(this idictionary<tkey, tvalue> dict,                                             tkey key, func<tkey, tvalue> creator) {     tvalue value;     if(!dict.trygetvalue(key, out value))     {         value = creator(key);         dict.add(key, value);     }     return value; } 

you call this:

var trader = traderset.getoradd(key, k => new trader(s.gateway, s.broker)); 

this a lot cleaner , shorter odd looking approach.

btw: use concurrentdictionary<tkey, tvalue> instead. class has method getoradd , has benefit of being thread safe.