A function to populate LIST collection

Gee Batol

Hi,

Coming from a primitive language like ansi-C,I'm new to C# so I really need your help. How do I write a function
that would loop through a given dataset and populate the list of courses tied up to the student,
then loop through the subjects tied up to the given course?

StudentName       Age         Courses                 SubjectsList
Prasad Singh       23         Bachelor of Arts        Subject 1
Prasad Singh       23         Bachelor of Business    Subject 11
Prasad Singh       23         Bachelor of Arts        Subject 2
Prasad Singh       23         Bachelor of Business    Subject 22
Nand Sawadi        42         Bachelor of Arts        Subject 8
Nand Sawadi        42         Bachelor of Engg        Subject 9
Rajaned Motupah    19         Diploma in Math         Subject 10
Rajaned Motupah    19         Diploma in Press        Subject 11
Rajaned Motupah    19         Diploma in Tourism      Subject 142
Rajaned Motupah    19         Diploma in Tourism      Subject 115
Mayar Karan        22         Certificate in English Subject 25

Class Student
{

String Name {get;set;}
Integer Age {get;set;}
List Courses {get; set;}

??? should I define another LIST here for subjects??
}

Thanks in advance for the help.

5 Replies

Know the answer? Post it — somebody with the same question will find it here.

Vulpes14y ago
Accepted answer
You're going to need 2 classes here - Student and Course. The latter will need to contain a list of subjects for the course.

Try the following:

using System;
using System.Collections.Generic;
using System.Data;

class Course
{
public string Name {get; set;}
public List Subjects {get; set;}

public Course(string name, List subjects)
{
Name = name;
Subjects = subjects;
}
}

class Student
{
public string Name {get; set;}
public int Age {get; set;}
public List Courses {get; set;}

public Student(string name, int age, List courses)
{
Name = name;
Age = age;
Courses = courses;
}

public override string ToString()
{
string temp = "";

foreach(Course c in Courses)
{
foreach(string s in c.Subjects)
{
temp += String.Format("{0}, {1}, {2}, {3}\n", Name, Age, c.Name, s);
}
}

return temp;
}
}

class Program
{
static void Main()
{
DataSet ds = new DataSet();
DataTable dt = new DataTable();
ds.Tables.Add(dt);
dt.Columns.Add("StudentName");
dt.Columns.Add("Age", typeof(int));
dt.Columns.Add("Course");
dt.Columns.Add("Subject");
dt.Rows.Add("Prasad Singh", 23, "Bachelor of Arts", "Subject 1");
dt.Rows.Add("Prasad Singh", 23, "Bachelor of Business", "Subject 11");
dt.Rows.Add("Prasad Singh", 23, "Bachelor of Arts", "Subject 2");
dt.Rows.Add("Prasad Singh", 23, "Bachelor of Business", "Subject 22");
dt.Rows.Add("Nand Sawadi", 42, "Bachelor of Arts", "Subject 8");
dt.Rows.Add("Nand Sawadi", 42, "Bachelor of Engg", "Subject 9");
dt.Rows.Add("Rajaned Motupah", 19, "Diploma in Math", "Subject 10");
dt.Rows.Add("Rajaned Motupah", 19, "Diploma in Press", "Subject 11");
dt.Rows.Add("Rajaned Motupah", 19, "Diploma in Tourism", "Subject 142");
dt.Rows.Add("Rajaned Motupah", 19, "Diploma in Tourism", "Subject 115");
dt.Rows.Add("Mayar Karan", 22, "Certificate in English", "Subject 25");

List students = new List();

foreach(DataRow dr in dt.Rows)
{
string name = (string)dr["StudentName"];
int age = (int)dr["Age"];
string courseName = (string)dr["Course"];
string subject = (string)dr["Subject"];

bool existingStudent = false;

foreach(Student s in students)
{
if (s.Name == name && s.Age == age)
{
bool existingCourse = false;

foreach(Course c in s.Courses)
{
if (c.Name == courseName)
{
c.Subjects.Add(subject);
existingCourse = true;
break;
}
}

if(!existingCourse)
{
List subjects = new List();
subjects.Add(subject);
s.Courses.Add(new Course(courseName, subjects));
}

existingStudent = true;
break;
}
}

if (!existingStudent)
{
List subjects = new List();
subjects.Add(subject);
List courses = new List();
courses.Add(new Course(courseName, subjects));
students.Add(new Student(name, age, courses));
}
}

// print out all students

foreach(Student s in students) Console.WriteLine(s);
Console.ReadKey();
}
}
Gee Batol14y ago
Hi Sam,

The dataset is created and ready by a stored procedure call, but some of the columns are redundant for that particular row, although one row is unique from each other, just some repeating columns. So Vulpes code is very helpful for me to figure out a Class design to layer the output.

Basically the final returned data is of a List<> form, so when I use this in a web service, the XML (soap output) will already be layered because of the list property.

Thanks guys.
Sam Hobbs14y ago
Vulpes tends to answer the question that is asked, but you might not be asking the right question.

If the data is coming from database tables, then you can create a SQL query to join the tables. That wouold make everything easier.

Even if the data is not coming from database tables, an alternative to what you are doing is to create a database in memory. More specifically, you can use the DataSet class cand create two tables with a relation between the tables. You could then use SQL the same as if the data was in a database.
Vulpes14y ago
That's right, Gee.

Layering is a good word to describe the process.
Gee Batol14y ago
This idea is what I have been looking for. So I need to create a LIST property inside the Course class, and then create a List property inside the Student class. So if there will be another sub-item under Subjects, I will have to create another class called Subject with a LIST property so that when I serialized this in XML it will be layered, right?

Your code is very helpful. Very much appreciated!

Thank you!