Update composite fields like fullname,address

my requirement is to retrieve views using c# . . i did that succesfully . .but in that sometimes i am getting fields internal name as "fullname" etc. which is composite field . . when i am trying to update the entity by refering these names there it is throwing error . . so how can i know that these fields are composite fields dynamically and while updating, how can i handle them to update entity succesfully.

Below for example i took "fullname":

if (dataRow[i].ToString() == string.Empty)
{
    selectedEntity["fullname"] = null;
}
else
{
    selectedEntity["fullname"] = "ms crm";
    //error
}

//it is not getting updated and throwing error
//"key is not present in dictionary"


for me the most imporatnt task is to know the field which i am trying to update is 
composite dynamically so that i dont have to handle them by hardcoding.