How to Convert a List Object to CSV and Download? C# .NET

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Threading.Tasks;

namespace ListToCsvConsole
{
    class Program
    {
        static void Main(string[] args)
        {
            //set up the list to pass to the convertToCsv
            var theList = new List<Person>();
            theList.Add(new Person
            {
                FirstName = "John",
                LastName = "Doe",
                BirthDate = new DateTime(1984, 05,12)
            });

            theList.Add(new Person
            {
                FirstName = "Jane",
                LastName = "Doe",
                BirthDate = new DateTime(1992, 01, 25)
            });

            //convert objects to csv and output results to concole
            Console.Write(covertToCsv<Person>(theList));
            Console.ReadKey();
        }

        //This is where the actual conversion happens
        private static string covertToCsv<theType>(List<theType> ListToConvert) where theType : class
        {
            List<List<string>> dataList = new List<List<string>>();
            
            //iterate through list items
            foreach (var item in ListToConvert)
            {
                //get properties and values 
                PropertyInfo[] props = item.GetType().GetProperties(BindingFlags.Public | BindingFlags.Instance);
                List<string> itemValues = new List<string>();
                
                //iterate through properties
                foreach (var prop in props)
                    itemValues.Add(prop.GetValue(item).ToString());
                
                dataList.Add(itemValues); 
            }

            //flatten out lists and return results
            return string.Join(Environment.NewLine, dataList.Select(i =>  string.Join(",", i.Select(v => v.ToString()))));
        }
    }

    // person class for demo purposes
    class Person
    {
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public DateTime BirthDate { get; set; }

    }
}

Thanks for the interesting piece. Could I suggest that you take advantage of the string.Join() method to build the string that you pass to the StringBuilder.AppendLine() method? It uses a StringBuilder internally to prevent the unnecessary creation of new strings. Something like this.

var sb = new StringBuilder();
List<string>dataList=new List<string>();
foreach (var data in lstData)
   {
       dataList.Add(data.Id,data.Name,data.City,data.Country,data.Continent);
       sb.AppendLine(string.Join(",", dataList));
       dataList.Clear();
   }

The string.Join() method works best when you have an existing list of strings. In this example, it is necessary to create a new list but I feel that the resulting code is neater, less repetitious and less error-prone. Best wishes, George