F.cs

namespace Serializer
{
    public class F {
        public int i1 { get; set; }
        public int i2 { get; set; }
        public int i3 { get; set; }
        public int i4 { get; set; }
        public int i5 { get; set; }
        
        public F(int i) { i1 = i; i2 = i + 1; i3 = i + 2; i4 = i + 3; i5 = i + 4; }
        public F() { }
    }
}

SerializerExtensions.cs

using System.Collections;
using System.ComponentModel;
using System.Linq;
using System.Text;

namespace Serializer
{
    static class SerializerExtentions
    {
        public static string ToCsv(this object obj, string separator)
        {
            var fields = obj.GetType().GetProperties();
            StringBuilder line = new StringBuilder(); 
            if (obj is string)
            {
                line.Append(obj as string);
                return line.ToString();
            }

            foreach (var field in fields)
            {
                var value = field.GetValue(obj);
                var name = field.Name;
                var fieldType = field.GetValue(obj).GetType();
                if (line.Length > 0)
                {
                    line.Append(separator);
                }

                line.Append(name.ToString()); line.Append(":"); 
                if (value is string) {
                    line.Append(value as string);
                }
                
                if (typeof(IEnumerable).IsAssignableFrom(fieldType)) {
                    var objectList = value as IEnumerable;
                    StringBuilder row = new StringBuilder();
                    foreach (var item in objectList) {
                        if (row.Length > 0) {
                            row.Append(separator);
                        }
                    row.Append(item.ToCsv(separator));
                }
                
                line.Append(row.ToString());
            }
            else
            {
                line.Append(value.ToString());
            }
        }
        
        return line.ToString();
    }

        public static object FromCSV<T>(this string csv, string separator) where T : new()
        {
            var parts = csv.Split(separator);
            var datum = new T();
            var fields = datum.GetType().GetProperties();
            for (int i = 0; i < parts.Length; i++) {
                var token = parts[i].Split(":");
                var property = token[0];
                var value = token[1];
                var p = fields.FirstOrDefault(a => a.Name.Equals(property));
                var converter = TypeDescriptor.GetConverter(p.PropertyType);
                var convertedvalue = converter.ConvertFrom(value); 
                p.SetValue(datum, convertedvalue);
            }
            return datum;
        }
    }
}