How to check if value already exixts in a list

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C#

public  class Logger
{
   string module { get; set; }
   private  string sMessage { get; set; }
   public static string sNewMessage = string.Empty;
   public static List<Logger> logMessages = new List<Logger>();
   private static string sLogMessage;

C#

private static void Log(string message, string type, string module)
{
 //here every message i entered is addedin a list now i want to check if message already exists ???do not add 
bool bMessageexists = logMessages.Contains(new Logger() { sMessage });

but even i entered existing message it returns false my code is not working correctly

What I have tried:

i have crated a list of string meggages which is ok for example HELLO message but i want to check if it already exists i mean if list already contains HELLO message then do not add in a list i have written a code above but its not working correctly even i entered same message 10 times bool returns false??

Posted 16-Nov-16 20:38pm

Member 11000455

Updated 16-Nov-16 21:19pm

Nelek

v3

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Ralf Meier 17-Nov-16 2:59am

Perhaps you should show the code behind each of your methods ...

1 solution

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Midi_Mick · Answer 1 · 2016-11-16T21:15:00

Solution 1

If your logger class exposes its current message, then you need to compare that:

C#

bool bMessageexists = logMessages.Contains(logger=>logger.Message == sMessage);

If not, you will need to override Logger.Equals, to compare the messages in both objects.

C#

class Logger {
    string sMessage;
    //...
    public override bool Equals(object obj) {
        if (obj is Logger)
            return sMessage == ((Logger)obj).sMessage;
        return false;
    }
}

Posted 16-Nov-16 21:15pm

Midi_Mick

Updated 16-Nov-16 22:37pm

v2

Comments

Afzaal Ahmad Zeeshan 17-Nov-16 3:19am

5ed.

Member 11000455 17-Nov-16 4:19am

logMessages.Add(new Logger() { sMessage = message });//here every time i add a message it is added to a list corretly

and i have done
bool bMessageexists = logMessages.Contains(new Logger() { sMessage = message}); //but it returns false.
tried ur code LINQ expression its not working

Midi_Mick 17-Nov-16 4:37am

Ok, now that you have included your Logger class definition, it's easier to answer.
Because you have declared sMessage as private, you will have to implement the Equals override in the Logger class (as per my answer above), as the Linq query does not have access to the field.
Note: If you override Equals, you also must override GetHashCode. In this case, I would simply return sMessage.GetHashCode() from that override.