The keyword
this
always refers to the current instance of the enclosing class.
You have one constructor missing, so the code should be:
class Student
{
public int student_ID = 0;
public string student_Fname = "";
public string student_Lname = "";
public string student_type = "";
public Student()
{
}
public Student(int ID)
: this(ID , "", "")
{
}
public Student(int ID, string Fname)
: this(ID, Fname,"")
{
}
public Student(int ID, string Fname, string Lname)
{
student_ID = ID;
student_Fname = Fname;
student_Lname = Lname;
}
}
so the construct
: this(ID, Fname,"")
just calls the constructor with three parameters (the last one I added);