If, else if not working

My condition is not working, Is only getting thru the first if  and is not checking the next else if and else.
This is just an example, is not my actual code, but the condition is the same.

What am I doing wrong and what can I do to make it check the else if and else conditions?
 
if (a != b) {
     Console.Writeline("not equal");
  }
//Not getting here or else
  else if (a == string.Empty) {
   Console.Writeline("is empty");
  }
  else {
   if (a == b) {
   Console.Writeline("They are equal");
  }
}
...