Added XMLDoc where needed

Supermarket/Food.cs

@@ -5,12 +5,22 @@ public sealed class Food : Product
     private const char AllergenSeparator = '|';
     private readonly SortedSet<AllergenType> _allergens;
     
+    /// <summary>
+    /// The constructor of Food
+    /// </summary>
+    /// <param name="productName">The product name</param>
+    /// <param name="barcode">The bar code</param>
+    /// <param name="quantity">The quantity</param>
+    /// <param name="allergens">The allergens</param>
     public Food(string productName, string barcode, int quantity, params AllergenType[] allergens)
         : base(productName, barcode, quantity)
     {
         _allergens = new SortedSet<AllergenType>(allergens);
     }
     
+    /// <summary>
+    /// The allergens
+    /// </summary>
     public AllergenType[] Allergens => _allergens.ToArray();
     
     protected override string[] CsvColumnNames => ["Barcode", "ProductName", "Quantity", "Allergens"];
@@ -24,6 +34,11 @@ public sealed class Food : Product
         }
     }
     
+    /// <summary>
+    /// Adds an allergen
+    /// </summary>
+    /// <param name="allergen">The allergen to add</param>
+    /// <returns>True if the allergen was successfully added, false otherwise</returns>
     public bool AddAllergen(AllergenType allergen)
     {
         if (ContainsAnyAllergen(allergen))
@@ -35,8 +50,18 @@ public sealed class Food : Product
         return true;
     }
     
+    /// <summary>
+    /// Removes an allergen
+    /// </summary>
+    /// <param name="allergen">The allergen to remove</param>
+    /// <returns>True if the allergen was successfully removed, false otherwise</returns>
     public bool RemoveAllergen(AllergenType allergen) => _allergens.Remove(allergen);
 
+    /// <summary>
+    /// Checks if the food contains any of the given allergens
+    /// </summary>
+    /// <param name="allergens">The allergens to check</param>
+    /// <returns>True if any of the allergens are contained, false otherwise</returns>
     public bool ContainsAnyAllergen(params AllergenType[] allergens)
     {
         foreach (var allergen in allergens)

Supermarket/NonFood.cs

@@ -12,8 +12,14 @@ public sealed class NonFood : Product
         _reviews = new List<Review>();
     }
     
+    /// <summary>
+    /// The list of reviews
+    /// </summary>
     public Review[] Reviews => _reviews.ToArray();
     
+    /// <summary>
+    /// The average rating
+    /// </summary>
     public double? AverageRating
     {
         get
@@ -36,6 +42,10 @@ public sealed class NonFood : Product
         AverageRating?.ToString("F1", CultureInfo.InvariantCulture) ?? String.Empty
     ];
     
+    /// <summary>
+    /// Adds a review
+    /// </summary>
+    /// <param name="review">The review to add</param>
     public void AddReview(Review review)
     {
         _reviews.Add(review);

Supermarket/Product.cs

@@ -6,6 +6,12 @@ public abstract class Product
 
     public const string Invalid = "Invalid!";
 
+    /// <summary>
+    /// The constructor of Product
+    /// </summary>
+    /// <param name="productName">The product name</param>
+    /// <param name="barcode">The bar code</param>
+    /// <param name="quantity">The quantity</param>
     protected Product(string productName, string barcode, int quantity)
     {
         if (string.IsNullOrWhiteSpace(productName))
@@ -17,22 +23,56 @@ public abstract class Product
         Quantity = quantity > 0 ? quantity : 0;
     }
 
+    /// <summary>
+    /// The product name
+    /// </summary>
     public string ProductName { get; }
 
+    /// <summary>
+    /// The bar code of the product
+    /// </summary>
     public string Barcode { get; }
 
+    /// <summary>
+    /// The quantity of the product
+    /// </summary>
     public int Quantity { get; }
     
+    /// <summary>
+    /// The CSV column names
+    /// </summary>
     protected virtual string[] CsvColumnNames => [nameof(Barcode), nameof(ProductName), nameof(Quantity)];
     
+    /// <summary>
+    /// The CSV column values
+    /// </summary>
     protected virtual string[] CsvColumnValues => [Barcode, ProductName, Quantity.ToString()];
     
+    /// <summary>
+    /// The CSV header
+    /// </summary>
+    /// <returns>The formatted CSV header</returns>
     public string GetCsvHeader() => string.Join(Separator, CsvColumnNames);
 
+    /// <summary>
+    /// The CSV line
+    /// </summary>
+    /// <returns>The formatted CSV line with values</returns>
     public string ToCsv() => ToCsvLine(CsvColumnValues, Separator);
 
+    /// <summary>
+    /// The CSV line generator
+    /// </summary>
+    /// <param name="values">The values</param>
+    /// <param name="separator">The separator</param>
+    /// <returns>The formatted CSV line</returns>
     protected static string ToCsvLine(string[] values, char separator) => String.Join(separator, values);
 
+    /// <summary>
+    /// Checks if the bar code is valid
+    /// </summary>
+    /// <param name="barcode">The bar code to check</param>
+    /// <returns>True if the bar code is valid, false otherwise</returns>
     public static bool IsBarcodeValid(string? barcode)
     {
         if (barcode == null)
@@ -75,6 +115,13 @@ public abstract class Product
         return calculatedCheckDigit == int.Parse(barcode[^1].ToString());
     }
     
+    /// <summary>
+    /// Appends new values to an existing array
+    /// </summary>
+    /// <param name="existingArray">The array to append to</param>
+    /// <param name="newValues">The array of values to append</param>
+    /// <typeparam name="T">The type</typeparam>
+    /// <returns>The complete array</returns>
     protected static T[] AppendToArray<T>(T[] existingArray, params T[] newValues)
     {
         // we are allowed to use Lists, so why not? :)