Fixed Product.cs & implemented NonFood.cs

Supermarket/NonFood.cs

@@ -9,32 +9,35 @@ public sealed class NonFood : Product
     public NonFood(string productName, string barcode, int quantity)
         : base(productName, barcode, quantity)
     {
-        // TODO
-        _reviews = null!;
-        Console.WriteLine($"Remove me, I just make code compile {_reviews}");
+        _reviews = new List<Review>();
     }
-
-    // TODO
-    public Review[] Reviews => null!;
+    
+    public Review[] Reviews => _reviews.ToArray();
     
     public double? AverageRating
     {
         get
         {
-            // TODO
-            return -1D;
+            if (_reviews.Count == 0)
+            {
+                return null;
+            }
+
+            return _reviews.Average(review => (double)review.Rating);
         }
     }
-
-    // TODO
-    protected override string[] CsvColumnNames => null!;
-
-    // TODO
-    // hint: .ToString("F1", CultureInfo.InvariantCulture)
-    protected override string[] CsvColumnValues => null!;
+    
+    protected override string[] CsvColumnNames => ["Barcode", "ProductName", "Quantity", "AverageRating"];
+    
+    protected override string[] CsvColumnValues => [
+        Barcode,
+        ProductName, 
+        Quantity.ToString("F0", CultureInfo.InvariantCulture), 
+        AverageRating?.ToString("F1", CultureInfo.InvariantCulture) ?? String.Empty
+    ];
     
     public void AddReview(Review review)
     {
-        // TODO
+        _reviews.Add(review);
     }
 }

Supermarket/Product.cs

@@ -8,6 +8,10 @@ public abstract class Product
 
     protected Product(string productName, string barcode, int quantity)
     {
+        if (string.IsNullOrWhiteSpace(productName))
+        {
+            productName = Invalid;
+        }
         ProductName = productName;
         Barcode = IsBarcodeValid(barcode) ? barcode : Invalid;
         Quantity = quantity > 0 ? quantity : 0;
@@ -26,10 +30,18 @@ public abstract class Product
     public string GetCsvHeader()
     {
         string header = String.Empty;
-        foreach (var columnName in CsvColumnNames)
+        for (var i = 0; i < CsvColumnNames.Length; i++)
         {
+            string columnName = CsvColumnNames[i];
+            
+            if(i == CsvColumnNames.Length - 1)
+            {
+                header += $"{columnName}";
+                break;
+            }
             header += $"{columnName}{Separator}";
         }
+
         return header;
     }
     
@@ -38,10 +50,18 @@ public abstract class Product
     protected static string ToCsvLine(string[] values, char separator)
     {
         string line = string.Empty;
-        foreach (var value in values)
+        for (var i = 0; i < values.Length; i++)
         {
+            string value = values[i];
+
+            if (i == values.Length - 1)
+            {
+                line += $"{value}";
+                break;
+            }
             line += $"{value}{separator}";
         }
+
         return line;
     }