How to clone a list: retarget net10.0, collection expression and GetRange, remove broken ToppingsList clone (#2210)

Move both projects from net7.0 to net10.0 and update the test stack (xunit 2.9.3, runner 4.0.0, Test.Sdk 18.10.1, coverlet 10.0.1, FluentAssertions 7.2.2).

Remove ToppingsList<T> and its test: its Clone() called MemberwiseClone(), which copies the private backing array by reference, so the clone shared storage with the original and was not a clone at all.

Add a collection-expression clone and a GetRange clone with tests, build the copy-constructor deep copy as a one-line projection, and add a test proving the projected clone keeps its toppings after the original is cleared.

Fix the ConverAll typo in the console output, make Pizza.Name and Pizza.Toppings required with [SetsRequiredMembers] on the copy constructor, and use First instead of FirstOrDefault. The folder now builds with 0 warnings and runs 11 of 11 tests.

Author: vladimir-pecanac-main

collections-lists/HowToCloneAList/HowToCloneAList.Tests/HowToCloneAList.Tests.csproj

@@ -1,22 +1,22 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net7.0</TargetFramework>
+    <TargetFramework>net10.0</TargetFramework>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
 
     <IsPackable>false</IsPackable>
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="FluentAssertions" Version="6.9.0" />
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.3.2" />
-    <PackageReference Include="xunit" Version="2.4.2" />
-    <PackageReference Include="xunit.runner.visualstudio" Version="2.4.5">
+    <PackageReference Include="FluentAssertions" Version="7.2.2" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.10.1" />
+    <PackageReference Include="xunit" Version="2.9.3" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="4.0.0">
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
       <PrivateAssets>all</PrivateAssets>
     </PackageReference>
-    <PackageReference Include="coverlet.collector" Version="3.1.2">
+    <PackageReference Include="coverlet.collector" Version="10.0.1">
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
       <PrivateAssets>all</PrivateAssets>
     </PackageReference>

collections-lists/HowToCloneAList/HowToCloneAList.Tests/PizzaTests.cs

@@ -1,4 +1,4 @@
-using FluentAssertions;
+using FluentAssertions;
 
 namespace HowToCloneAList.Tests
 {
@@ -60,5 +60,29 @@ public void GivenAValidPizza_WhenToStringMethodIsInvoked_ThenToStringMethodMetho
 
             expectedOutput.Should().Be(margherita.ToString());
         }
+
+        [Fact]
+        public void GivenAListOfPizzas_WhenProjectedThroughTheCopyConstructor_ThenTheCloneKeepsItsToppings()
+        {
+            var pizzas = new List<Pizza>
+            {
+                new Pizza
+                {
+                    Name = "Margherita",
+                    Toppings = new List<string>
+                    {
+                        "Mozzarella",
+                        "Olive oil",
+                        "Basil"
+                    }
+                }
+            };
+
+            List<Pizza> clone = [.. pizzas.Select(p => new Pizza(p))];
+
+            pizzas[0].Toppings.Clear();
+
+            clone[0].Toppings.Should().HaveCount(3);
+        }
     }
-}
+}

collections-lists/HowToCloneAList/HowToCloneAList.Tests/Tests.cs

@@ -56,5 +56,27 @@ public void GivenAValidList_WhenConvertAllMethodIsInvoked_ThenConvertAllMethodRe
 
             listClone.Should().BeEquivalentTo(list);
         }
+
+        [Fact]
+        public void GivenAValidList_WhenACollectionExpressionIsUsed_ThenTheCollectionExpressionReturnsNewListInstance()
+        {
+            var list = new List<string> { "one", "two", "three" };
+
+            List<string> listClone = [.. list];
+
+            listClone.Should().BeEquivalentTo(list);
+            listClone.Should().NotBeSameAs(list);
+        }
+
+        [Fact]
+        public void GivenAValidList_WhenGetRangeMethodIsInvoked_ThenGetRangeMethodReturnsNewListInstance()
+        {
+            var list = new List<string> { "one", "two", "three" };
+
+            var listClone = list.GetRange(0, list.Count);
+
+            listClone.Should().BeEquivalentTo(list);
+            listClone.Should().NotBeSameAs(list);
+        }
     }
 }

collections-lists/HowToCloneAList/HowToCloneAList.Tests/ToppingsListTests.cs

@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>net7.0</TargetFramework>
+    <TargetFramework>net10.0</TargetFramework>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
   </PropertyGroup>

collections-lists/HowToCloneAList/HowToCloneAList/HowToCloneAList.csproj

@@ -1,19 +1,22 @@
-namespace HowToCloneAList
+using System.Diagnostics.CodeAnalysis;
+
+namespace HowToCloneAList
 {
     public class Pizza : ICloneable
     {
         public Pizza()
         {
         }
 
+        [SetsRequiredMembers]
         public Pizza(Pizza pizza)
         {
             Name = pizza.Name;
             Toppings = pizza.Toppings.ToList();
         }
 
-        public string Name { get; set; }
-        public List<string> Toppings { get; set; }
+        public required string Name { get; set; }
+        public required List<string> Toppings { get; set; }
 
         public object Clone()
         {

collections-lists/HowToCloneAList/HowToCloneAList/Pizza.cs

@@ -24,22 +24,18 @@ static void Main(string[] args)
             var toppingsClonedWithConvertAll = toppings
                 .ConvertAll(new Converter<string, string>(x => x));
 
-            var customToppingsList = new ToppingsList<string>
-            {
-                "Mozzarella",
-                "Olive oil",
-                "Basil"
-            };
+            List<string> toppingsClonedWithCollectionExpression = [.. toppings];
 
-            var toppingsClonedWithICloneable = (ToppingsList<string>)customToppingsList.Clone();
+            var toppingsClonedWithGetRange = toppings.GetRange(0, toppings.Count);
 
             Console.WriteLine("Original list: " + string.Join(", ", toppings));
             Console.WriteLine("Cloned with Constructor: " + string.Join(", ", toppingsClonedWithConstructor));
             Console.WriteLine("Cloned with CopyTo: " + string.Join(", ", toppingsClonedWithCopyTo));
             Console.WriteLine("Cloned with AddRange: " + string.Join(", ", toppingsClonedWithAddRange));
             Console.WriteLine("Cloned with ToList: " + string.Join(", ", toppingsClonedWithToList));
-            Console.WriteLine("Cloned with ConverAll: " + string.Join(", ", toppingsClonedWithConvertAll));
-            Console.WriteLine("Cloned with ICloneable: " + string.Join(", ", toppingsClonedWithICloneable));
+            Console.WriteLine("Cloned with ConvertAll: " + string.Join(", ", toppingsClonedWithConvertAll));
+            Console.WriteLine("Cloned with a collection expression: " + string.Join(", ", toppingsClonedWithCollectionExpression));
+            Console.WriteLine("Cloned with GetRange: " + string.Join(", ", toppingsClonedWithGetRange));
 
             var pizzas = new List<Pizza>
             {
@@ -74,15 +70,10 @@ static void Main(string[] args)
                 pizzasClonedWithICloneable.Add((Pizza)pizza.Clone());
             }
 
-            var pizzasClonedWithCopyConstructor = new List<Pizza>();
-
-            foreach (var pizza in pizzas)
-            {
-                pizzasClonedWithCopyConstructor.Add(new Pizza(pizza));
-            }
+            List<Pizza> pizzasClonedWithCopyConstructor = [.. pizzas.Select(p => new Pizza(p))];
 
             var margherita = pizzas
-                .FirstOrDefault(x => x.Name == "Margherita");
+                .First(x => x.Name == "Margherita");
 
             margherita.Toppings.Clear();