C#C
C#•3y ago•
47 replies
Just Some Bread

Object reference set to an instance of an object.

Hi, just completing an assignment for uni that reads marks from a file and calculate the exam percentage and grade then outputs it to the console with the number of students who had that grade in the file. I came across a NullReferenceException and I'm not sure how to handle it. 

using System;
using System.IO;

namespace Program{
    class Program{
        static void Main(string[] args){
            string currFile = "5StudentsOneEachClassification.mark";
            string[][] studentInfo = loadDataFromFile(currFile);
            outputClassification(studentInfo);
        }
        static string[][] loadDataFromFile(string currFile){
            string data = File.ReadAllText(System.IO.Directory.GetCurrentDirectory()+"/TestInputFiles/"+currFile);
            string[] splitData = data.Split(new char[]{'\n'});
            string[][] studentInfo = new string[splitData.Length-1][];
            double capstoneTotal = 0, examTotal = 0, challTotal = 0, total = 0;

            for(int i = 0; i<splitData.Length-1;i++){
                string[] temp = splitData[i].Split(new char[]{':', '[', ']', ' ', ','});
                for(int x = 0; x<temp.Length-1; x++){
                    
                    if(temp[i] == "ID"){
                        studentInfo[i][0] = temp[i];
                    }
                    else if(temp[i] == "Challenges"){
                        challTotal = Convert.ToInt32(temp[i+2]) + Convert.ToInt32(temp[i+3]) + Convert.ToInt32(temp[i+4]) + Convert.ToInt32(temp[i+5]) + Convert.ToInt32(temp[i+6]) + Convert.ToInt32(temp[i+7]) + Convert.ToInt32(temp[i+8]) + Convert.ToInt32(temp[i+9]) + Convert.ToInt32(temp[i+10]) + Convert.ToInt32(temp[i+11]);
                    }
                    else if(temp[i] == "Exam"){
                        examTotal = Convert.ToInt32(temp[i+1]);
                    }
                    else if(temp[i] == "Capstone"){
                        capstoneTotal = Convert.ToInt32(temp[i+1]);
                    }
                    else if(temp[i] == "FirstName"){
                        studentInfo[i][0] = temp[i+1];
                    }
                    else if(temp[i] == "LastName"){
                        studentInfo[i][1] = temp[i+1];
                    }
                }
                challTotal = Math.Round((challTotal/35)*100, 2);
                examTotal = Math.Round((examTotal/7)*100, 2);
                capstoneTotal = Math.Round((capstoneTotal/100)*100, 2);
                total = (challTotal*50/100) + (examTotal*25/100) + (capstoneTotal*25/100);

                studentInfo[i][2] = Convert.ToString(total);
            }
            return studentInfo;
        }

        static void outputClassification(string[][] studentInfo){   
            int first = 0, two1 = 0, two2 = 0, third = 0, fail = 0;
            for(int i = 0; i<studentInfo.Length-1; i++){
                if(Convert.ToInt32(studentInfo[i][2]) >=  70){
                    first++;
                }
                else if(Convert.ToInt32(studentInfo[i][2]) >= 60){
                    two1++;
                }
                else if(Convert.ToInt32(studentInfo[i][2]) >= 50){
                    two2++;
                }
                else if(Convert.ToInt32(studentInfo[i][2]) >= 40){
                    third++;
                }
                else{
                    fail++;
                }
            }
            Console.WriteLine($"{first} - First");
            Console.WriteLine($"{two1} - 2:1");
            Console.WriteLine($"{first} - First");
            Console.WriteLine($"{third} - Third");
            Console.WriteLine($"{fail} - Fail");
        }
    }
}
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