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Home Interviews How can you write a list of objects to a CSV file manually (without a library)? – MindStick
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1 Answers

ICSM Computer
ICSM Computer 14 May 2025
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To write a list of objects to a CSV file manually (without using a third-party library like CsvHelper), you can use System.IO.StreamWriter and reflection or direct property access.

Example: Write a List of Objects to CSV

Model:

public class Person
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string Email { get; set; }
}

Writing to CSV:

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

public class CsvWriterExample
{
    public static void WriteCsv(string path, List<Person> people)
    {
        using (var writer = new StreamWriter(path))
        {
            // Write header
            writer.WriteLine("Id,Name,Email");

            foreach (var person in people)
            {
                // Escape commas and quotes if necessary
                string line = $"{Escape(person.Id.ToString())},{Escape(person.Name)},{Escape(person.Email)}";
                writer.WriteLine(line);
            }
        }
    }

    private static string Escape(string field)
    {
        if (field.Contains(",") || field.Contains("\"") || field.Contains("\n"))
        {
            // Escape quotes and wrap in quotes
            field = field.Replace("\"", "\"\"");
            return $"\"{field}\"";
        }
        return field;
    }
}

Usage:

var people = new List<Person>
{
    new Person { Id = 1, Name = "John", Email = "john@example.com" },
    new Person { Id = 2, Name = "Jane, A.", Email = "jane@example.com" }, // comma in name
};

CsvWriterExample.WriteCsv("people.csv", people);

Why Use Escape()?

  1. CSV fields must be quoted if they contain:
  2. Commas ,
  3. Newlines \n
  4. Double quotes "
  5. Double quotes in a field must be escaped as "" and the entire field wrapped in quotes.
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