c# - Dictonary return object having count -1 ArithemeticFlowException -


i facing issue in arithmetic overflow, have posted detail in question [dictonary tolist arithmeticflowexception

however have found reason, when call method 

global.sereverconnections.trygetvalue(key, out connections);

it throws overflow exception, having count of connections equal -1.

public static  idictionary<string, iset<connectionmanager>> sereverconnections = new concurrentdictionary<string, iset<connectionmanager>>();   public static ilist<connectionmanager> getuserconnections(string username)     {         //key must not null in case return null if send , empty username         if (string.isnullorempty(username))             return null;         iset<connectionmanager> connections;          global.sereverconnections.trygetvalue(username, out connections);         //this make copy of          //return (connections != null ? connections.tolist() ?? enumerable.empty<connectionmanager>().tolist() : null);           //exception occurs in below line, , connections.count==-1         return (connections != null ? connections.tolist() : null);      }

global.sereverconnections concurrentdictionary, , thread-safe. adding hashsets - , not thread-safe.

you can't call hashset.tolist() @ same time someone adding items it.

you need use locking around accesses hashset ensure don't have threading issues. or switch using concurrentdictionary instead of hashset (as per https://stackoverflow.com/questions/18922985/concurrent-hashsett-in-net-framework).


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