C# structure: student records application

Exercise:

Write a C# program to keep records and perform statistical analysis for a class of 20 students. The information of each student contains ID, Name, Sex, quizzes Scores (2 quizzes per semester), mid-term score, final score, and total score.
The program will prompt the user to choose the operation of records from a menu as shown below:
========================================================
                                                   MENU
========================================================
1. Add student records

2. Delete student records

3. Update student records

4. View all student records

5. Calculate an average of a selected student’s scores

6. Show student who gets the max total score

7. Show student who gets the min total score

8. Find student by ID
9. Sort records by total scores

Enter your choice:1


Note: All students records are stored in an array of structures
Solution:
To make this solution simple and easy to follow, we divide this solution in to different steps:
Step1: Declaring a structure called student to store the records
struct student

{
public string stnumber;

public string stname;

public string sex;

public float quizz1;

public float quizz2;

public float assigment;

public float midterm;

public float final;

public float total;


};

C# structure: student records application



Menu of choices

Step2: Defining the displaymenu() method to display the menu. The simple menu provides nine choices from 1 to 9 to work with the records.
static void displaymenu(){

Console.WriteLine("=====================================================");

Console.WriteLine(" MENU ");

Console.WriteLine("=====================================================");

Console.WriteLine(" 1.Add student records");
Console.WriteLine(" 2.Delete student records");
Console.WriteLine(" 3.Update student records");
Console.WriteLine(" 4.View all student records");
Console.WriteLine(" 5.Calculate an average of a selected student's scores");
Console.WriteLine(" 6.Show student who get the max total score"); 
Console.WriteLine(" 7.Show student who get the min total score");
Console.WriteLine(" 8.Find a student by ID");
Console.WriteLine(" 9.Sort students by TOTAL");



}

C# structure: student records application



Append record to list

Step3: defining the add(student[] st, ref int itemcount) method to add a new record to the the array of student objects. This method takes two arguments. The first argument is the array of student objects(st) and the second argument is the number of items in the array. The two arguments are passed by references. For an array, we don't need to use the ref keyword when we want to pass it by reference. However, we need to use the ref keyword when we want to pass an argument of primitive type such as int, float, dobule,etc. When the new item is added the value itemcount variable increases by 1 that means the number of records in the list increases.
//method add/append a new record
static void add(student[] st,ref int itemcount){

Again:
Console.WriteLine(); 
Console.Write("Enter student's ID:");
st[itemcount].stnumber=Console.ReadLine().ToString() ;
//making sure the record to be added doesn't already exist
if(search(st,st[itemcount].stnumber,itemcount)!=-1){

Console.WriteLine("This ID already exists.");
goto Again;

}


Console.Write("Enter student's Name:"); 

st[itemcount].stname=Console.ReadLine ().ToString();


Console.Write("Enter student's Sex(F or M):");
st[itemcount].sex=Console.ReadLine().ToString();


Console.Write("Enter student's quizz1 score:");
st[itemcount].quizz1=float.Parse(Console.ReadLine());


Console.Write("Enter student's quizz2 score:");
st[itemcount].quizz2=float.Parse(Console.ReadLine());


Console.Write("Enter student's assigment score:");
st[itemcount].assigment=float.Parse(Console.ReadLine());


Console.Write("Enter student's mid term score:");
st[itemcount].midterm=float.Parse(Console.ReadLine());

Console.Write("Enter student's final score:");
st[itemcount].final=float.Parse(Console.ReadLine());

st[itemcount].total=st[itemcount].quizz1+st[itemcount].quizz2+st[itemcount].assigment+st[itemcount].midterm+st[itemcount].final;



++itemcount; //increase the number of items by one



}

C# structure: student records application



Show all records in list

Step4: Defining the viewall(student[] st, int itemcount) method to display the list of all records in the set. To display all records, we need a while loop to traverse through the array of student objects.

static void viewall(student[] st,int itemcount)
{

int i = 0;

Console.WriteLine("{0,-5}{1,-20}{2,-5}{3,-5}{4,-5}{5,-5}{6,-5}{7,-5}{8}(column index)", "0", "1", "2", "3", "4", "5", "6", "7", "8");
Console.WriteLine("{0,-5}{1,-20}{2,-5}{3,-5}{4,-5}{5,-5}{6,-5}{7,-5}{8,-5}", "ID", "NAME", "SEX", "Q1", "Q2", "As", "Mi", "Fi", "TOTAL");

Console.WriteLine("=====================================================");

while (i < itemcount)
{

if (st[i].stnumber !=null )
{

Console.Write("{0,-5}{1,-20}{2,-5}", st[i].stnumber, st[i].stname, st[i].sex);

Console.Write("{0,-5}{1,-5}{2,-5}",st[i].quizz1,st[i].quizz2,st[i].assigment);

Console.Write("{0,-5}{1,-5}{2,-5}",st[i].midterm,st[i].final,st[i].total);

Console.Write("\n");
}

i = i + 1;



}

}

C# structure: student records application



Find record index

Step5: Defining the search(student[] st, int itemcount) method to search for the index of a target record. This method is useful as we need it to find the location of the target record in the array of student objects. It can help us to make sure the record does exit before we allow the record for deletion or updating. If the target element is found, the method returns the index of this element. It return -1, if the target element is not found in the array.

static int search(student[] st, string id,int itemcount){
int found =-1;
for (int i = 0; i < itemcount && found==-1; i++)
{

  if (st[i].stnumber == id) found=i;

  else found=-1 ;
}

return found;

}

C# structure: student records application



Delete record

Step6: Defining the delete(student[] st, ref int itemcount) method to delete a target record from the array of student objects. The user will be prompted to enter the id of student record that his/her want to delete. Then this id will be checked to make sure it does exist in the list. If the target record or element really exists, the deletion process can be made. The deletion process starts by checking whether the target record is the last record, beginning or middle record. If the target record is the last record in the list, we simply delete the record by supplying it to the clean(student[] st, int index) method. The last record is the record that has it index equal to itemcount subtracted by 1. If the target record stays at the beginning or in the middle of the list, we need to use a loop to allow the previous element to take over the next element. This process continue until it reaches the end of the list(itemcount-1). Then the clean() method is called to clean the last element of the list that should not exit. After the element is cleaned, the itemcount variable decreases by 1. This means that the number of elements in the list decreases.

static void delete(student[] st, ref int itemcount)
{
string id;
int index;
if (itemcount > 0)
{
Console.Write("Enter student's ID:");
id = Console.ReadLine();
index = search(st, id.ToString(),itemcount); 

if ((index!=-1) && (itemcount != 0))
{
if (index == (itemcount-1)) //delete the last record
{

clean(st, index);
--itemcount;

Console.WriteLine("The record was deleted.");
}
else //delete the first or middle record
{
for (int i = index; i < itemcount-1; i++)
{
st[i] = st[i + 1];
clean(st, itemcount);
--itemcount ;
}

}

}
else Console.WriteLine("The record doesn't exist. Check the ID and try again.");


}
else Console.WriteLine("No record to delete");
}

static void clean(student[] st,int index)
{
st[index].stnumber = null;
st[index].stname = null;
st[index].sex = null;
st[index].quizz1 = 0;
st[index].quizz2 = 0;
st[index].assigment = 0;
st[index].midterm = 0;
st[index].final = 0;
st[index].total = 0;

}

C# structure: student records application



Update record

Step7: Defining the update_rec(struct student st[], int itemcount) method to update a specified record. The update process starts by asking the user to input the id of the record to be changed. The id value is check to make sure it really exists. If it exits the change to the target record can be made after asking the user to input the new value of the field that need change.

static void update(student[] st, int itemcount)
{
string id;
int column_index;
Console.Write("Enter student's ID:");
id=Console.ReadLine();
Console.Write("Which field you want to update(1-7)?:");
column_index=int.Parse(Console.ReadLine());

int index = search(st, id.ToString(),itemcount);

if ((index != -1) && (itemcount != 0))
{
if (column_index == 1)
{
Console.Write("Enter student's Name:");

st[index].stname = Console.ReadLine().ToString();
}

else if (column_index == 2)
{
Console.Write("Enter student's Sex(F or M):");
st[index].sex = Console.ReadLine().ToString();
}
else if (column_index == 3)
{
Console.Write("Enter student's quizz1 score:");
st[index].quizz1 = float.Parse(Console.ReadLine());
}
else if (column_index == 4)
{
Console.Write("Enter student's quizz2 score:");
st[index].quizz2 = float.Parse(Console.ReadLine());
}
else if (column_index == 5)
{
Console.Write("Enter student's assigment score:");
st[index].assigment = float.Parse(Console.ReadLine());
}
else if (column_index == 6)
{
Console.Write("Enter student's mid term score:");
st[index].midterm = float.Parse(Console.ReadLine());
}
else if (column_index == 7)
{
Console.Write("Enter student's final score:");
st[index].final = float.Parse(Console.ReadLine());
}
else Console.WriteLine("Invalid column index");
st[index].total = st[index].quizz1 + st[index].quizz2 + st[index].assigment + st[index].midterm + st[index].final;


}
else Console.WriteLine("The record deosn't exits.Check the ID and try again.");

} 

C# structure: student records application



Average score

Step8: Defining the average(student[] st, int itemcount) method to calculate the average score of a selected student. The method alo starts by asking the user to input the id of the target student. This id is checked to make sure it really exist. The average score can be calculated by dividing the sum of quizz1 score, quizz2 score, assignment score, mid-term score, and final score by 5.
static void average(student[] st, int itemcount)
{
string id;
float avg=0;
Console.Write("Enter students'ID:");
id = Console.ReadLine();
int index = search(st, id.ToString(),itemcount);
if (index != -1 && itemcount>0)
{
st[index].total = st[index].quizz1 + st[index].quizz2 + st[index].assigment + st[index].midterm + st[index].final;
avg = st[index].total /5;
}

Console.WriteLine("The average score is {0}.", avg);
}

C# structure: student records application



Min and Max scores

Step9: Defining the showmax(student[] st, int itemcount) and showmin(student[] st, int itemcount) methods show about the student who gets the maximum score and the student who gets the minimum score. To find the highest total core or lowest total core, we need to compare every total score of each element.
static void showmax(student[] st, int itemcount)
{
float max = st[0].total;
int index=0;
Console.WriteLine(itemcount);
if (itemcount >= 2)
{

for (int j = 0; j < itemcount-1; ++j)
if (max < st[j+1].total) {
max = st[j+1].total;
index = j+1;

}


}

else if (itemcount == 1)
{
index = 0;
max = st[0].total;
}


else Console.WriteLine("Not record found!");

if (index != -1) Console.WriteLine("The student with ID:{0} gets the highest score {1}.", st[index].stnumber, max);


}
\

static void showmin(student[] st, int itemcount)
{

float min = st[0].total;
int index = 0;
if (itemcount >= 2)
{
for (int j = 0; j < itemcount-1; ++j)
if (min > st[j+1].total)
{
min = st[j+1].total;
index = j+1;

}



}

else if (itemcount == 1)
{
index = 0;
min = st[0].total;
}
else Console.WriteLine("No record found!");

if (index != -1) Console.WriteLine("The student with ID:{0} gets the lowest score {1}.", st[index].stnumber, min);


}
//method to find record
static void find(student[] st, int itemcount)
{
string id;
Console.Write("Enter student's ID:");
id=Console.ReadLine();

int index=search(st,id.ToString(),itemcount);
if (index != -1)
{
Console.Write("{0,-5}{1,-20}{2,-5}", st[index].stnumber, st[index].stname, st[index].sex);

Console.Write("{0,-5}{1,-5}{2,-5}", st[index].quizz1, st[index].quizz2, st[index].assigment);

Console.Write("{0,-5}{1,-5}{2,-5}", st[index].midterm, st[index].final, st[index].total);
Console.WriteLine(); 

}
else Console.WriteLine("The record deosn't exits.");

}