This keword when used as with constractor chainning refers to the current instance or to the parameter

Question

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C#

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,"")
     {

     }
}

in the current code this keword when used as with constractor chainning refers to the current instance or to the parameter

What I have tried:

just read about it but think it is refer to the current parameter not to the current instance of the class

Posted 5-Aug-19 4:41am

Member 14479161

Updated 5-Aug-19 5:31am

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Afzaal Ahmad Zeeshan 5-Aug-19 13:47pm

No, it does not target the current parameters, why would you think that? :-)

2 solutions

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Richard MacCutchan · Accepted Answer · 2019-08-05T04:45:00

The keyword this always refers to the current instance of the enclosing class.

You have one constructor missing, so the code should be:

C#

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 , "", "")  // call the final constructor that takes 3 parameters
     {
     }

     public Student(int ID, string Fname)
         : this(ID, Fname,"") // same as above
     {
     }
     public Student(int ID, string Fname, string Lname)
     {
         // set the values of the fields of the class.
         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);

OriginalGriff · Accepted Answer · 2019-08-05T05:31:00

Solution 2

This this specific case the this refers to overloads of the constructor of the instance. It's the equivelant of writing this code:

C#

public Student()
{
}

public Student(int ID)
{
    BuildIt(ID , "", "");
}

public Student(int ID, string Fname)
{
    BuildIt(ID, Fname, "");
}

Posted 5-Aug-19 5:31am

OriginalGriff

Comments

Richard MacCutchan 5-Aug-19 14:53pm

BuildIt?

OriginalGriff 6-Aug-19 2:23am

A hypothetical method to use the parameters