How can you call MapAttributesForExport and read from csentry

Hello!

I must say that I'm new to MIM.
I have understood that this method MapAttributesForExport below is used for preparing the Connector space with data that will be used for export. When you have export flow that you can flow direct from MV to CS you don't need to specify them in MapAttributesForExport. 
Can somebody explain how is it possible to read from csentry as is done in this method below. I can't understand that. 

void IMASynchronization.MapAttributesForExport(string FlowRuleName, MVEntry mventry, CSEntry csentry)
        {
            bool sentOk = false;

            if (csentry["sentOk"].IsPresent)
            {
                if (csentry["sentOk"].Value.ToLower() == "true")
                {
                    sentOk = true;
                }
            }

 switch (FlowRuleName)
            {
                case "message":
                    //Sätt/uppdatera endast värden endast om inte alla mail redan skickats
                    if (sentOk == false)
                    {
                        if (csentry["objectType"].Value.ToString().ToLower() == "employee")
                        {

//Tony