Unreachable code detected

It is because you have written some code after the return statement, which are not getting executed.
 
That's why the codes written after the return statement are unreachable.
And the type variable is not used, only assigned.
So, your code should look like below.

public string getInformation()
{
     string type = ""; // Use string.Empty instaed of "".

     // You can do this like courseType.Equals(yourVariable); inside if statement, 
     // where yourVariable will contain the character to compare.
     if (courseType == 'c') 
     {
          type = "HNC";
          // try to use this "type" variable or else it is unnecessary.
     }
 
     return (id + " " + Convert.ToString(courseType) + " " + Convert.ToString(CourseCode));
}

 
Note
I just corrected the current code. If you face any other problems with your logic, then you have to solve that. Otherwise it should work.