CSV File I/O

When to Use CSV Files

Use CSV files for tabular data with consistent fields across all records. Easy to transfer between programs and spreadsheets.

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Student Result Class

public class StudentResult
{
    public int StudentID { get; set; }
    public string FirstName { get; set; } = "";
    public string LastName { get; set; } = "";
    public int Score { get; set; }
}

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CSV File Helper Class

Click to view CsvFileHelper.cs

using System;
using System.Collections.Generic;
using System.IO;

public static class CsvFileHelper
{
    // Path constant (recommended for Unit 3)
    private const string CSV_PATH = "data/students.csv";

    public static List<StudentResult> LoadStudentResults()
    {
        var results = new List<StudentResult>();
        if (!File.Exists(CSV_PATH)) return results;

        var lines = File.ReadAllLines(CSV_PATH);
        if (lines.Length <= 1) return results; // header only or empty

        for (int i = 1; i < lines.Length; i++) // start after header
        {
            var parts = lines[i].Split(','); // delimiter = comma

            // Basic safety check
            if (parts.Length != 4) continue;

            results.Add(new StudentResult
            {
                StudentID = int.Parse(parts[0]),
                FirstName = parts[1],
                LastName = parts[2],
                Score = int.Parse(parts[3])
            });
        }

        return results;
    }

    public static void SaveStudentResults(List<StudentResult> results)
    {
        var lines = new List<string> { "StudentID,FirstName,LastName,Score" };

        foreach (var r in results)
        {
            lines.Add($"{r.StudentID},{r.FirstName},{r.LastName},{r.Score}");
        }

        File.WriteAllLines(CSV_PATH, lines);
    }
}

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Usage Example

// Read all lines from CSV file
string[] lines = File.ReadAllLines("students.csv");

// First line is the header (skip it when processing data)
Console.WriteLine("Header: " + lines[0]);

// Process data rows (starting from index 1)
for (int i = 1; i < lines.Length; i++)
{
    // Split each line by comma to get individual fields
    string[] fields = lines[i].Split(',');

    string studentID = fields[0];   // "1023"
    string firstName = fields[1];   // "Aisha"
    string lastName = fields[2];    // "Khan"
    string score = fields[3];       // "87"

    Console.WriteLine($"{firstName} {lastName} scored {score}");
}

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Example CSV File Structure

StudentID,FirstName,LastName,Score,Grade,House
1023,Aisha,Khan,87,A,Kendall
1024,Luca,Rossi,91,A,O'Brien
1025,Emma,Smith,76,B,Mackillop

Note

CSV gets tricky if fields can contain commas (e.g., surnames like "Smith, Jr"). That's one reason XML can be preferable for messy real data.