String input to a class variable in c#

Question

I'm new to C# and I tried making a "Student" class that takes the student name and few other things. I have a problem at taking student name as I get an exception when typing the name as input.

In declaration,

public class Student
{
     public string studentName;// this one
     public long studentID;
     public int score1;
     ...etc
}

then I have inside Main:

Student[] student = new Student[N];
// the N is determined by a previous block    of code.
for (int i = 0; i < N; i++)
{
    check = false; // ignore this one.
    Console.WriteLine("Student {0}", i + 1);
    Console.Write("\t \t Name: ");
    string input = Console.ReadLine();
    student[i].studentName = input; 
    // I get an exception at that last line, after typing whatever string.I feel like I've done something horribly wrong.
}

Thanks :)

Welcome to Stack Overflow! Please go through the tour, the help center and the how to ask a good question sections to see how this site works and to help you improve your current and future questions, which can help you get better answers. — help-info.de
– help-info.de, Commented Jun 18, 2016 at 8:48
An unhandled exception of type 'System.NullReferenceException' occurred in RandomCoding.exe — MoodyW
– MoodyW, Commented Jun 18, 2016 at 8:49

Orel Eraki · Accepted Answer · 2016-06-18 08:48:10Z

4

You declared an Array of Student but you didn't initialized it with Student instances. i.e student[i] is null.

After

for (int i = 0; i < N; i++) {

You should do

student[i] = new Student();
// Rest of the code.

answered Jun 18, 2016 at 8:48

Orel Eraki

12.2k4 gold badges31 silver badges38 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

MoodyW Over a year ago

First line: Student[] student = new Student[N];

Orel Eraki Over a year ago

No, I mean inside the loop. new Student[N] only reserve the space, it doesn't allocate the space. Add the line i gave you as the first line in the loop, or right before you're using student[i], and it will fix the issue.

MoodyW Over a year ago

Worked! Basically what happened is that I allocated the N number of Student needed, but I didn't allocate the memory for each one of them right ? thanks again :)

Alexander · Accepted Answer · 2016-06-18 08:49:51Z

0

using System;
using System.Collections.Generic;

public class Student
{
     public string studentName { get;set;}
     public long studentID;
     public int score1;
}

public class Test
{
    public static void Main()
    {
         var students = new List<Student>();
         for (int i = 0; i < 3; i++)
         {
             Console.WriteLine("Student {0}", i + 1);
             Console.Write("\t \t Name: ");
             string input = Console.ReadLine();
             students.Add(new Student {studentName = input });
         }                     
    }
}

answered Jun 18, 2016 at 8:49

Alexander

6074 gold badges11 silver badges23 bronze badges

Comments

Siamak Ferdos · Accepted Answer · 2016-06-18 08:54:17Z

0

Student[] student = new Student[N];
// the N is determined by a previous block    of code.
for (int i = 0; i < N; i++)
{
    student[i] = new Student();
    check = false; // ignore this one.
    Console.WriteLine("Student {0}", i + 1);
    Console.Write("\t \t Name: ");
    string input = Console.ReadLine();
    student[i].studentName = input; 
}

answered Jun 18, 2016 at 8:54

Siamak Ferdos

3,3096 gold badges35 silver badges60 bronze badges

Comments

Evan Dangol · Accepted Answer · 2016-06-18 12:47:47Z

0

for (int i = 0; i < N; i++)
{
    check = false; // ignore this one.
    Console.WriteLine("Student {0}", i + 1);
    Console.Write("\t \t Name: ");
    string input = Console.ReadLine();
you are missing line below.
     student[i]= new student();
    student[i].studentName = input; 

}

answered Jun 18, 2016 at 12:47

Evan Dangol

2513 silver badges2 bronze badges

Collectives™ on Stack Overflow

String input to a class variable in c#

4 Answers 4

3 Comments

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

3 Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related