Object initialization in CSharp

Question

When i have declaration like:

class Professor
{
  string profid;
  public string ProfessorID
  {
     get { return profid;}
     set { profid=value;}
  }

  student st;

}


class student
{
  string name;
  string id;
  public string Name
  {
     get  { return name;}
     set  { name=value; } 
  }

 public string StudentID
 {
   get { return id;}
   set { id=value; }
 }

}


public void GetDetails()
{
  Professor prf=new Professor(){ ProfessorID=1, how to initialize student here?};

}

Inside GetDetails() how can i initialize student ?

Answer 1

Your Professor class will need a property setter for the student, at which point you can write:

public void GetDetails()
{
    Professor prf = new Professor { 
        ProfessorID = "1", 
        Student = new Student { Name = "Jon", StudentID = "1" }
    };    
}

Without that property, nothing in the Professor class will set the st variable at all.

Note that because in both cases we're only using the parameterless constructor, I've removed the explicit () from the object initializer.

Further note: automatically implemented properties can make your code a lot shorter:

class Professor
{
    public string ProfessorID { get; set; }
    public Student Student { get; set; }
}

class Student
{
    public string Name { get; set; }
    public string StudentID { get; set; }
}

Answer 2

You should make property Student in Professor:

class Professor
{
    string profid;
    public string ProfessorID
    {
        get { return profid; }
        set { profid = value; }
    }

    student st;

    public student Student { // New property
        get { return st; }
        set { st = value; }
    }
}


class student
{
    string name;
    string id;
    public string Name
    {
        get { return name; }
        set { name = value; }
    }

    public string StudentID
    {
        get { return id; }
        set { id = value; }
    }

}


public void GetDetails(){
    Professor prf=new Professor(){ ProfessorID="1", Student = new student()};
}

Answer 3

First make it accessible:

public student Student { get; set; }

then something like:

Professor prf = new Professor()
{
    ProfessorID = "abc",
    Student = new student { Name = "Marc", StudentID = "def" }
};

Note that if the property is get-only:

private readonly student _student = new student();  
public student Student { get { return _student; }}

Then you can use the alternative syntax (which sets properties without attempting to change the student reference):

Professor prf = new Professor()
{
    ProfessorID = "abc",
    Student = { Name = "Marc", StudentID = "def" }
};

Answer 4

You need an accessor for your student within Professor

class Professor
{
  string profid;
  public string ProfessorID
  {
     get { return profid;}
     set { profid=value;}
  }

  public Student {
     get { return st;}
     set { st=value;}
  }

  student st;

}


public void GetDetails()
{
  Student s = new Student();
  s.StudentId = someId;
  s.name = someName;
  Professor prf = new Professor { ProfessorID=1, Student = s;};
}

However, your current model is 1 Prof : 1 Student, are you sure this is what you want?

Answer 5

Following up on John's answer:

You want parentheses, not brackets, but a public constructor is typically the right approach. The other way to do it is a no-argument constructor with public properties.