How To Add Items In A Multi-Dimensional Jagged Array?

Question

I am trying to add items to an already existing jagged array and I am having some trouble. My program is a console application that is used to deal with student grades (adding students, deleting students, changing names, adding grades to various students, etc). I am reading in a sequential file that contains student ID, name, and then the grades (0-100) for each student. I decided to use a jagged array because I don't know how many grades each student will have, nor do I know how many students I will have.

Right now I am trying to add grades to existing students. My text file looks like this:

 00000,Mimzi Dagger,100,50,75,70,45,10,98,83
 00001,Alexander Druaga,89,45,80,90,15,73,99,100,61
 00002,Nicholas Zarcoffsky,100,50,80,50,75,100,100
 00003,Kantmiss Evershot,50,100

I want to be able to use a For loop and search for the student ID that the user enters, once I find that student ID I want to add a grade under that student. Here is a piece of my code, but it doesn't work.

for (int i = 0; i < studentArray.Length; i++)
{
    if (studentID == studentArray[i][0])
    {
        studentArray[i][studentArray[i].Length + 1] = newGrade;
    }
}

Answer 1

While this is something that I would never, ever do in the real world... I think it does satisfy your constraints for the assignment.

class Program
{
    static void Main(string[] args)
    {

        List<List<string>> dataList = new List<List<string>>();

        dataList.Add(new List<string> { "00000", "Mimzi Dagger", "100", "50", "75", "70", "45",    "10", "98", "83" });
        dataList.Add(new List<string> { "00001", "Alexander Druaga", "89", "45", "80", "90", "15", "73", "99", "100", "61" });
        dataList.Add(new List<string> { "00002", "Nicholas Zarcoffsky", "100", "50", "80", "50", "75", "100", "100" });
        dataList.Add(new List<string> { "00003", "Kantmiss Evershot", "50", "100" });

        for (int i = 0; i < dataList.Count; i++)
        {
            foreach (var item in dataList[i])
            {
                Console.WriteLine(item);
            }
        }

        Console.ReadLine();

    }
}

Answer 2

This would be the most basic way of doing what you want:

for (int i = 0; i < studentArray.Length; i++)
{
    if (studentID == studentArray[i][0])
    {
        Array.Resize(ref studentArray[i], studentArray[i].Length + 1);
        studentArray[i][studentArray[i].Length - 1] = newGrade;
    }
}

Personally I find that a bit of a brain pain.

I'd rather write it like this:

for (int i = 0; i < studentArray.Length; i++)
{
    if (studentID == studentArray[i][0])
    {
        studentArray[i] =
            studentArray[i]
                .Concat(new [] { newGrade })
                .ToArray();
    }
}