Try:
string result = status == 1 ? "Approved" : status == 2 ? "Reject" : "Pending";
However, I would use a switch instead:
switch (status)
{
case 1: result = "Approved"; break;
case 2: result = "Reject"; break;
case 3: result = "Pending"; break;
default: result = "ERROR"; break;
}