using a hasehtable

inna grech

I have 2 lists in my program one that store objects of type student and another one which stores objects of type marks.

I have 3 methods one that inputs the details of the students, one that inputs the marks and one to view student details and their marks. My question is how I can use a hash table to get the Id of a student and then use it to input the marks and then how to retrieve both the student details and their marks altogether.

Please help me if you can.

public class Student
    {
        private string name;
        private string surname;
        private string dob;
        private string address;
        private string id;
        private string Name_2;
        private string Surname_2;


        public Student()
        {
            //empty contructor
        }

        public Student(string name, string surname, string dob, string address, string id)
        {
            this.name = name;
            this.surname = surname;
            this.dob = dob;
            this.address = address;
            this.id = id;
        }

        public Student(string Name_2, string Surname_2)
        {
            // TODO: Complete member initialization
            this.Name_2 = Name_2;
            this.Surname_2 = Surname_2;
        }

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

        public string Surname
        {
            get { return surname; }
            set { surname = value; }

        }

        public string DOB
        {
            get { return dob; }
            set { dob = value; }
        }

        public string Addr
        {
            get { return address; }
            set { address = value; }

        }

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

    }
}

public struct Marks
{
    private int hyexam;
    private int anexam;

    public int HYEXAM
    {
        get { return hyexam; }
        set { hyexam = value; }
    }

    public int ANEXAM
    {
        get { return anexam; }
        set { anexam = value; }

    }

    public Marks(int hyexam, int anexam)
    {
        this.hyexam = hyexam;
        this.anexam = anexam;
    }

    public double OverallExam()
    {
        return (0.4 * hyexam) + (0.6 * anexam);
    }


}

 public class JuniorStudents : Student
    {
        public int numofStudents;
        public Marks Mathematics;
        public Marks English;
        public Marks Maltese;
        public Marks ReligiousStudies;
        public Marks SocialStudies;


        const string filestud = "C:\\Users\\Maria\\Desktop\\Students.txt";
        const string filemarks= "C:\\Users\\Maria\\Desktop\\Marks.txt";
        public List<Student> studentList = new List<Student>();
        public List<Marks> markslist = new List<Marks>();

        public void ReadStudentsRecords()
        {

           try
            {
                string name;
                string surname;
                string dob;
                string addr;
                string id;
                StreamReader myFile = File.OpenText(filestud);
                while (myFile.ReadLine() != null)
                {
                    name = myFile.ReadLine();
                    surname=myFile.ReadLine();
                    dob=myFile.ReadLine();
                    addr=myFile.ReadLine();
                    id=myFile.ReadLine();
                    Student st = new Student(name, surname, dob, addr, id);
                    studentList.Add(st);

                }
                myFile.Close();
            }
            catch (Exception e)
            {
                e.ToString();
            }

            }

        public void ReadMarksList()
        {
            try {                     
                StreamReader myFile = File.OpenText(filemarks);
                while (myFile.ReadLine() != null)
                {
                        Mathematics.HYEXAM = myFile.Read();
                        Mathematics.ANEXAM = myFile.Read();
                        English.HYEXAM = myFile.Read();
                        English.ANEXAM = myFile.Read();
                        Maltese.HYEXAM = myFile.Read();
                        Maltese.ANEXAM = myFile.Read();
                        ReligiousStudies.HYEXAM = myFile.Read();
                        ReligiousStudies.ANEXAM = myFile.Read();
                        SocialStudies.HYEXAM = myFile.Read();
                        SocialStudies.ANEXAM = myFile.Read();

                        markslist.Add(Mathematics);
                        markslist.Add(English);
                        markslist.Add(Maltese);
                        markslist.Add(ReligiousStudies);
                        markslist.Add(SocialStudies);
                }
                myFile.Close();
            }
            catch (Exception e)
            {
                e.ToString();
            }
        }



        public void WriteStudentRecords()
        {   
            try
            {
                StreamWriter myFile = File.CreateText(filestud);
                foreach (Student s in studentList)
                {
                    myFile.WriteLine(s.ToString());
                }
                myFile.Close();
            }
            catch (Exception e)
            {
                e.ToString();
            }
        }

        public void WriteMarksRecords()
        {
             try
            {
                StreamWriter myFile = File.CreateText(filemarks);
                foreach (Marks m in markslist)
                {
                    myFile.WriteLine(m.ToString());
                }
                myFile.Close();
            }
            catch (Exception e)
            {
                e.ToString();
            }
        }


        public void AddStudentRecord()
        {

            Student stud = new Student(Name,Surname,DOB,Addr,Id);
            studentList.Add(stud);

            //bool error = false;
            //if (error == false)
            //{
            //    try
            //    {
            //        stud.Name = name;
            //        stud.Surname = surname;
            //        stud.DOB = dob;
            //        stud.Addr = address;
            //        stud.Id = id;

            //    }
            //    catch (FormatException ex)
            //    {
            //        error = true;
            //        Console.WriteLine(ex.ToString());
            //    }

                studentList.Add(stud);
                //myFile.WriteLine(studentList);
               // numofStudents = studentList.Count;
            }
          //  return 1;

        public void AddMarksRecord(int mthyexam,int mtanexam, int enhyexam, int enanexam, int mlhyexam, int mlanexam, int rshyexam,int rsanexam, int sshyexam, int ssanexam)
        {
             bool error=false;
            if (error==false)
                try{
            Mathematics.HYEXAM= mthyexam;
            Mathematics.ANEXAM= mtanexam;
            English.HYEXAM = enhyexam;
            English.ANEXAM = enanexam;
            Maltese.HYEXAM = mlhyexam;
            Maltese.ANEXAM = mlanexam;
            ReligiousStudies.HYEXAM = rshyexam;
            ReligiousStudies.ANEXAM = rsanexam;
            SocialStudies.HYEXAM = sshyexam;
            SocialStudies.ANEXAM = ssanexam;


               }
                catch  (FormatException ex){
                error=true;
                Console.WriteLine (ex.ToString());
                }

            markslist.Add(Mathematics);
            markslist.Add(English);
            markslist.Add(Maltese);
            markslist.Add(ReligiousStudies);
            markslist.Add(SocialStudies);

4 Replies

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Hemant Srivastava13y ago
I got very busy for a couple of days...Yes you may use everywhere hashtable wherever you are using list.
inna grech14y ago
Hi thanks for your reply. Do I keep the list of students or I remove it and make the hashtable instead? And then how could I use the marks hash table please because I didn't understand that part. I want to add student marks according to the student id and then after adding a student and adding marks according to the id I show all the student details together with their marks.

rasul moh14y ago

AuthorReply

inna grech

using a hasehtable
Posted on: 23 Nov 2012

I have 2 lists in my program one that store objects of type student and another one which stores objects of type marks.

Please help me if you can.

public class Student     {         private string name;         private string surname;         private string dob;         private string address;         private string id;         private string Name_2;         private string Surname_2;           public Student()         {             //empty contructor         }          public Student(string name, string surname, string dob, string address, string id)         {             this.name = name;             this.surname = surname;             this.dob = dob;             this.address = address;             this.id = id;         }          public Student(string Name_2, string Surname_2)         {             // TODO: Complete member initialization             this.Name_2 = Name_2;             this.Surname_2 = Surname_2;         }          public string Name         {             get { return name; }             set { name = value; }         }          public string Surname         {             get { return surname; }             set { surname = value; }          }          public string DOB         {             get { return dob; }             set { dob = value; }         }          public string Addr         {             get { return address; }             set { address = value; }          }          public string Id         {             get { return id; }             set { id = value; }         }      } }  public struct Marks {     private int hyexam;     private int anexam;      public int HYEXAM     {         get { return hyexam; }         set { hyexam = value; }     }      public int ANEXAM     {         get { return anexam; }         set { anexam = value; }      }      public Marks(int hyexam, int anexam)     {         this.hyexam = hyexam;         this.anexam = anexam;     }      public double OverallExam()     {         return (0.4 * hyexam) + (0.6 * anexam);     }   }   public class JuniorStudents : Student     {         public int numofStudents;         public Marks Mathematics;         public Marks English;         public Marks Maltese;         public Marks ReligiousStudies;         public Marks SocialStudies;           const string filestud = "C:\\Users\\Maria\\Desktop\\Students.txt";         const string filemarks= "C:\\Users\\Maria\\Desktop\\Marks.txt";         public List<Student> studentList = new List<Student>();         public List<Marks> markslist = new List<Marks>();          public void ReadStudentsRecords()         {             try             {                 string name;                 string surname;                 string dob;                 string addr;                 string id;                 StreamReader myFile = File.OpenText(filestud);                 while (myFile.ReadLine() != null)                 {                     name = myFile.ReadLine();                     surname=myFile.ReadLine();                     dob=myFile.ReadLine();                     addr=myFile.ReadLine();                     id=myFile.ReadLine();                     Student st = new Student(name, surname, dob, addr, id);                     studentList.Add(st);                  }                 myFile.Close();             }             catch (Exception e)             {                 e.ToString();             }              }          public void ReadMarksList()         {             try {                                      StreamReader myFile = File.OpenText(filemarks);                 while (myFile.ReadLine() != null)                 {                         Mathematics.HYEXAM = myFile.Read();                         Mathematics.ANEXAM = myFile.Read();                         English.HYEXAM = myFile.Read();                         English.ANEXAM = myFile.Read();                         Maltese.HYEXAM = myFile.Read();                         Maltese.ANEXAM = myFile.Read();                         ReligiousStudies.HYEXAM = myFile.Read();                         ReligiousStudies.ANEXAM = myFile.Read();                         SocialStudies.HYEXAM = myFile.Read();                         SocialStudies.ANEXAM = myFile.Read();                          markslist.Add(Mathematics);                         markslist.Add(English);                         markslist.Add(Maltese);                         markslist.Add(ReligiousStudies);                         markslist.Add(SocialStudies);                 }                 myFile.Close();             }             catch (Exception e)             {                 e.ToString();             }         }            public void WriteStudentRecords()         {                try             {                 StreamWriter myFile = File.CreateText(filestud);                 foreach (Student s in studentList)                 {                     myFile.WriteLine(s.ToString());                 }                 myFile.Close();             }             catch (Exception e)             {                 e.ToString();             }         }          public void WriteMarksRecords()         {              try             {                 StreamWriter myFile = File.CreateText(filemarks);                 foreach (Marks m in markslist)                 {                     myFile.WriteLine(m.ToString());                 }                 myFile.Close();             }             catch (Exception e)             {                 e.ToString();             }         }           public void AddStudentRecord()         {              Student stud = new Student(Name,Surname,DOB,Addr,Id);             studentList.Add(stud);              //bool error = false;             //if (error == false)             //{             //    try             //    {             //        stud.Name = name;             //        stud.Surname = surname;             //        stud.DOB = dob;             //        stud.Addr = address;             //        stud.Id = id;              //    }             //    catch (FormatException ex)             //    {             //        error = true;             //        Console.WriteLine(ex.ToString());             //    }                  studentList.Add(stud);                 //myFile.WriteLine(studentList);                // numofStudents = studentList.Count;             }           //  return 1;          public void AddMarksRecord(int mthyexam,int mtanexam, int enhyexam, int enanexam, int mlhyexam, int mlanexam, int rshyexam,int rsanexam, int sshyexam, int ssanexam)         {              bool error=false;             if (error==false)                 try{             Mathematics.HYEXAM= mthyexam;             Mathematics.ANEXAM= mtanexam;             English.HYEXAM = enhyexam;             English.ANEXAM = enanexam;             Maltese.HYEXAM = mlhyexam;             Maltese.ANEXAM = mlanexam;             ReligiousStudies.HYEXAM = rshyexam;             ReligiousStudies.ANEXAM = rsanexam;             SocialStudies.HYEXAM = sshyexam;             SocialStudies.ANEXAM = ssanexam;                  }                 catch  (FormatException ex){                 error=true;                 Console.WriteLine (ex.ToString());                 }              markslist.Add(Mathematics);             markslist.Add(English);             markslist.Add(Maltese);             markslist.Add(ReligiousStudies);             markslist.Add(SocialStudies);

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Hemant Srivastava

Re: using a hasehtable
Posted on: 23 Nov 2012

For student hashtable, you could create as (the place where you are creating list):

public Hashtable stuHashTable= new Hashtable();

Then you can add student records into hashtable like
(where you are adding student record into your list):

if(!stuHashTable.ContainsKey((string)id))                    
{                        
//Insert new student not duplicate coz hash table won't allow you 
//to have duplicate keys                        
stuHashTable.Add(id,st);                    
}

But for your Marks class, I want to suggest you that instead of creating marks class
create a "Subject_Marks" class
in which you could have following fields :

private string subject_Id;
private int hyexam;
private int anexam;

(For example: Subject_Id = 1 for Maths, 2 for English, 3 for SocialStudies etc.)

Then create hashtable for "Subject_Marks"

public Hashtable marksHashTable= new Hashtable();

You can iterate any hashtable with "DictionaryEntry", refer to following link for hashtable iteration:
http://www.mindfiresolutions.com/How-To-Iterate-the-Hashtable-in-C-311.php

Hemant Srivastava14y ago

For student hashtable, you could create as (the place where you are creating list):

public Hashtable stuHashTable= new Hashtable();

Then you can add student records into hashtable like
(where you are adding student record into your list):

if(!stuHashTable.ContainsKey((string)id))                    
{                        
//Insert new student not duplicate coz hash table won't allow you 
//to have duplicate keys                        
stuHashTable.Add(id,st);                    
}