A function to populate LIST collection

Question

Hi Coming from a primitive language like ansi-CI'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.

Vulpes · 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}
 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 Batol · Answer

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 Hobbs · Answer

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.

Vulpes · Answer

That's right Gee. Layering is a good word to describe the process.

Gee Batol · Answer

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!