Upload project.

Data-Import/CSVUtils.cs

@@ -0,0 +1,11 @@
+using System.IO;
+
+namespace Data_Import
+{
+    public static class CSVUtils
+    {
+        public static void WriteCSV(string[] csv, string filename) => File.WriteAllLines(filename, csv);
+
+        public static string[] ReadCSV(string filename) => File.ReadAllLines(filename);
+    }
+}

Data-Import/Car.cs

@@ -0,0 +1,48 @@
+using System;
+using System.Runtime.CompilerServices;
+
+namespace Data_Import
+{
+    class Car
+    {
+        private string registration;
+        public string Registration { get; set; }
+        public string Make { get; set; }
+        public string Model { get; set; }
+
+        public string Colour { get; set; }
+        public string FuelType { get; set; }
+
+        public bool HasValidRegistration()
+        {
+            //The order of these if statements could be improved, however they are written in this order for readability.
+            if (Registration.Length != 8)
+                return false;
+            if (!char.IsLetter(Registration[0]) || !char.IsLetter(Registration[1]))
+                return false;
+            if (!char.IsNumber(Registration[2]) || !char.IsNumber(Registration[3]))
+                return false;
+            if (Registration[4] != ' ')
+                return false;
+            if (!char.IsLetter(Registration[5]) || !char.IsLetter(Registration[6]) || !char.IsLetter(Registration[7]))
+                return false;
+            return true;
+        }
+
+        public string AsCSV()
+        {
+            return string.Format("{0},{1},{2},{3},{4}", Registration, Make, Model, Colour, FuelType);
+        }
+
+        public Car FromCSV(string csv)
+        {
+            var splitCSV = csv.Split(',');
+            Registration = splitCSV[0];
+            Make = splitCSV[1];
+            Model = splitCSV[2];
+            Colour = splitCSV[3];
+            FuelType = splitCSV[4];
+            return this;
+        }
+    }
+}

Data-Import/Data-Import.csproj

@@ -0,0 +1,9 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>netcoreapp3.1</TargetFramework>
+    <RootNamespace>Data_Import</RootNamespace>
+  </PropertyGroup>
+
+</Project>

Data-Import/Program.cs

@@ -0,0 +1,62 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Data_Import
+{
+    class Program
+    {
+        static void Main(string[] args)
+        {
+            var carContext = GetCarsFromCSV("data.csv").ToList();
+
+            ExportCSVsByFuelType(carContext);
+
+            var validCars = GetValidCars(carContext);
+            Console.WriteLine("Valid Cars:\n");
+            foreach(var c in validCars)
+            {
+                Console.WriteLine(c.AsCSV());
+            }
+            Console.WriteLine();
+
+            var invalidCarCount = carContext.Count - validCars.Count();
+            Console.WriteLine(String.Format("Invalid Car Count:\n{0}", invalidCarCount));
+        }
+
+        private static void ExportCSVsByFuelType(List<Car> cars)
+        {
+            //Could use a map here?
+            List<string> petrolCars = new List<string>(), dieselCars = new List<string>();
+            
+            foreach (var c in cars)
+            {
+                if (c.FuelType == "Petrol")
+                    petrolCars.Add(c.AsCSV());
+                else if (c.FuelType == "Diesel")
+                    dieselCars.Add(c.AsCSV());
+            }
+
+            CSVUtils.WriteCSV(petrolCars.ToArray(), "petrol.csv");
+            CSVUtils.WriteCSV(dieselCars.ToArray(), "diesel.csv");
+        }
+
+        private static IEnumerable<Car> GetValidCars(List<Car> cars)
+        {
+            foreach (var car in cars)
+            {
+                if (car.HasValidRegistration())
+                    yield return car;
+            }
+        }
+
+        private static IEnumerable<Car> GetCarsFromCSV(string filename)
+        {
+            foreach(var carString in CSVUtils.ReadCSV(filename))
+            {
+                var c = new Car();
+                yield return c.FromCSV(carString);
+            }
+        }
+    }
+}

Data-Import/data.csv

@@ -0,0 +1,41 @@
+Car Registration,Make,Model,Colour,Fuel
+B640 BBJ,Peugeot,106,Red,Petrol
+NJ13 LXX,Ford,Fiesta,Blue,Petrol
+B640BBJ,VW,Golf,Black,Diesel
+LD57 RTE,Audi,A4,Grey,Petrol
+RB65 ROB,Seat,Cupra,Black,Petrol
+SK67 HSB,Nissan,Leaf,Green,Electric
+NHZ 6842,Seat,Ibiza,Black,Petrol
+NDR 543R,Volkswagen,Golf,Yellow,Diesel
+SK67 HSB,Porsche,911,Red,Petrol
+AD58 LDR,Mercedes,C Class,Silver,Petrol
+NDJ64 XYZ,Fiat,500,White,Petrol
+LT59 MAJ,Ford,Mondeo,Silver,Diesel
+MD60XBA,Ford,Fiesta,Silver,Diesel
+X201JKL,Jeep,Compass,Orange,Petrol
+SL12 JBV,Hyundai,i40,Grey,Deisel
+RB66 OLP,Audi,A1,White,petrol
+SN18 DDF,Hyundai,i20,Green,Petrol
+TR10 NNB,Renault,Megane,Blue,Petrol
+PO13 DFS,BMW,M4,Green,Petral
+KR09 RVN,Kia,C'eed,White,Petrol
+KR59DFE,Vauxhall,Corsa,Orange,Diesel
+X913 UOP,Toyota,Prius,Black,Hybrid
+CY21 MSK,Tesla,Cybertruck,Silver,Electric
+UL66 OPL,Ford,Mustang,Green,Diesel
+UE13 URT,Audi,RS6,Blue,Desel
+WE66 AFG,BMW,135i,Grey,Petrol
+JO19 FRS,Pegeot,Partner,White,Diesel
+JM13 LKO,Hyundai,i10,Black,Petrol
+DF66 ORT,Citreon,Saxo,Mustard,Petrol
+GL65 DOW,Suzuki,GSX100,Blue,Petrol
+VB07 QKD,Tesla,Model 3,Red,Electric
+NI55 SAN,Nissan,Juke,Yello,Petrol
+XL13 PSR,Mini,Cooper,Red,Petrol
+JW18 HSV,Nissan,Micra,Red,Petrol
+FL61 JER,Ford,Mustang,Yellow,Petrol
+DP67 IOA,Peugeot,3008,Black,Petrol
+DL56 0PP,Audi,S4,Red,Diesel
+WRI5 TYI,BMW,I3,White,Electric
+QO59 OTL,BMW,Coupe 3,Black,Petrol
+HJ66 NSF,Renault,Clio,Blue,Petrol