Task.CompletedTask vs Task.FromResult vs return: retarget net10.0, drop redundant async, add notification handler example (#2208)

- Retarget both projects from net7.0 to net10.0
- Bump Microsoft.NET.Test.Sdk to 18.10.1, xunit to 2.9.3, xunit.runner.visualstudio to 4.0.0, coverlet.collector to 10.0.1
- UseTaskFromResultAsync() drops async/await and returns Task.FromResult(message) directly
- Remove UseTaskCompletedSync() and UseTaskFromResultSync(), and their calls in Program.cs
- Add INotificationHandler and ConsoleNotificationHandler, the imposed-signature case for Task.CompletedTask
- Add two tests asserting both factory-returned tasks are already complete without being awaited

Author: vladimir-pecanac-main

async-csharp/TaskCompletedTaskFromResultVsReturnInCSharp/TaskCompletedVsTaskFromResultVsReturnInCSharp/ConsoleNotificationHandler.cs

@@ -0,0 +1,11 @@
+namespace TaskCompletedVsTaskFromResultVsReturnInCSharp;
+
+public class ConsoleNotificationHandler : INotificationHandler
+{
+    public Task HandleAsync(string message)
+    {
+        Console.WriteLine(message);
+
+        return Task.CompletedTask;
+    }
+}

async-csharp/TaskCompletedTaskFromResultVsReturnInCSharp/TaskCompletedVsTaskFromResultVsReturnInCSharp/INotificationHandler.cs

@@ -0,0 +1,6 @@
+namespace TaskCompletedVsTaskFromResultVsReturnInCSharp;
+
+public interface INotificationHandler
+{
+    Task HandleAsync(string message);
+}

async-csharp/TaskCompletedTaskFromResultVsReturnInCSharp/TaskCompletedVsTaskFromResultVsReturnInCSharp/Program.cs

@@ -2,11 +2,9 @@
 
 var taskCompletedClass = new TaskCompletedHandler();
 await taskCompletedClass.UseTaskCompletedAsync();
-taskCompletedClass.UseTaskCompletedSync();
 
 var taskFromResultClass = new TaskFromResultHandler();
 await taskFromResultClass.UseTaskFromResultAsync();
-taskFromResultClass.UseTaskFromResultSync();
 
 var returnClass = new ReturnHandler();
 await returnClass.UseReturnAsync();

async-csharp/TaskCompletedTaskFromResultVsReturnInCSharp/TaskCompletedVsTaskFromResultVsReturnInCSharp/TaskCompletedHandler.cs

@@ -8,11 +8,4 @@ public Task UseTaskCompletedAsync()
 
         return Task.CompletedTask;
     }
-
-    public void UseTaskCompletedSync()
-    {
-        Console.WriteLine("Performing a synchronous work.");
-
-        Task.CompletedTask.Wait();
-    }
 }

async-csharp/TaskCompletedTaskFromResultVsReturnInCSharp/TaskCompletedVsTaskFromResultVsReturnInCSharp/TaskCompletedVsTaskFromResultVsReturnInCSharp.csproj

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

async-csharp/TaskCompletedTaskFromResultVsReturnInCSharp/TaskCompletedVsTaskFromResultVsReturnInCSharp/TaskFromResultHandler.cs

@@ -2,21 +2,12 @@
 
 public class TaskFromResultHandler
 {
-    public async Task<string> UseTaskFromResultAsync()
+    public Task<string> UseTaskFromResultAsync()
     {
         Console.WriteLine("Not performing any asynchronous work but returning a result.");
 
         var message = "Hello, world!";
 
-        return await Task.FromResult(message);
-    }
-
-    public string UseTaskFromResultSync()
-    {
-        Console.WriteLine("Performing a synchronous work.");
-
-        var message = "Hello, world!";
-
-        return Task.FromResult(message).Result;
+        return Task.FromResult(message);
     }
 }

async-csharp/TaskCompletedTaskFromResultVsReturnInCSharp/Tests/TaskCompletedVsTaskFromResultVsReturnInCSharpTests.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net7.0</TargetFramework>
+    <TargetFramework>net10.0</TargetFramework>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
 
@@ -10,13 +10,13 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <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="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>

async-csharp/TaskCompletedTaskFromResultVsReturnInCSharp/Tests/TaskCompletedVsTaskFromResultVsReturnTests.cs

@@ -31,4 +31,24 @@ public async Task WhenCallingUseReturnAsync_ThenUseReturn()
 
         Assert.Equal(20, result);
     }
+
+    [Fact]
+    public void WhenCallingUseTaskFromResultAsync_ThenTaskIsAlreadyComplete()
+    {
+        var taskFromResultClass = new TaskFromResultHandler();
+
+        var result = taskFromResultClass.UseTaskFromResultAsync();
+
+        Assert.True(result.IsCompletedSuccessfully);
+    }
+
+    [Fact]
+    public void WhenCallingHandleAsync_ThenTaskIsAlreadyComplete()
+    {
+        INotificationHandler handler = new ConsoleNotificationHandler();
+
+        var result = handler.HandleAsync("Order 42 shipped.");
+
+        Assert.True(result.IsCompletedSuccessfully);
+    }
 }