Custom Attributes in .NET: retarget to net10.0, add the reading-API examples

aspnetcore-features/CustomAttributes/CustomAttributes/CustomAttributeClasses.cs

@@ -1,74 +1,87 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Reflection;
-using System.Text;
-using System.Threading.Tasks;
-
-namespace CustomAttributes
+using System.Reflection;
+
+namespace CustomAttributes;
+
+public static class CustomAttributeHelper
 {
-    public static class CustomAttributeHelper
+    private static void WriteOnTheConsole(Attribute attributeInstance)
     {
-        private static void WriteOnTheConsole(Attribute attributeInstance)
-        {
-            var pInfoList = attributeInstance.GetType().GetProperties(BindingFlags.Public |
-                    BindingFlags.Instance |
-                    BindingFlags.DeclaredOnly);
+        var pInfoList = attributeInstance.GetType().GetProperties(BindingFlags.Public |
+                BindingFlags.Instance |
+                BindingFlags.DeclaredOnly);
 
-            Console.WriteLine($"\nThe {attributeInstance} attribute:");
+        Console.WriteLine($"\nThe {attributeInstance} attribute:");
 
-            foreach (var pInfo in pInfoList)
-                Console.WriteLine($"The {pInfo.Name} property is: {pInfo.GetValue(attributeInstance)}");
-        }
+        foreach (var pInfo in pInfoList)
+            Console.WriteLine($"The {pInfo.Name} property is: {pInfo.GetValue(attributeInstance)}");
+    }
 
-        public static string? GetAttribute(Type desiredType, Type desiredAttribute)
-        {
-            var attributeInstance = Attribute.GetCustomAttribute(desiredType, desiredAttribute);
+    public static string? GetAttribute(Type desiredType, Type desiredAttribute)
+    {
+        var attributeInstance = Attribute.GetCustomAttribute(desiredType, desiredAttribute);
 
-            if (attributeInstance == null)
-                Console.WriteLine($"The class {desiredType} does not have atributes.");
-            else
-                WriteOnTheConsole(attributeInstance);
+        if (attributeInstance == null)
+            Console.WriteLine($"The class {desiredType} does not have attributes.");
+        else
+            WriteOnTheConsole(attributeInstance);
 
-            return attributeInstance?.ToString();
-        }
+        return attributeInstance?.ToString();
+    }
+
+    public static T? GetAttributeGeneric<T>(Type desiredType) where T : Attribute
+    {
+        return desiredType.GetCustomAttribute<T>();
+    }
+
+    public static bool HasAttribute<T>(Type desiredType) where T : Attribute
+    {
+        return desiredType.IsDefined(typeof(T));
+    }
 
-        public static List<string> GetAttributesOfMethods(Type elementType)
+    public static List<string> GetAttributesOfMethods(Type elementType)
+    {
+        var attributes = new List<string>();
+
+        var methodInfoList = elementType.GetMethods(BindingFlags.Public |
+            BindingFlags.Instance |
+            BindingFlags.DeclaredOnly);
+
+        if (methodInfoList.Length == 0)
         {
-            List<string> attributes = new List<string>();
+            Console.WriteLine($"The type {elementType} does not have any methods.");
+            return attributes;
+        }
 
-            var methodInfoList = elementType.GetMethods(BindingFlags.Public |
-                BindingFlags.Instance |
-                BindingFlags.DeclaredOnly);
+        foreach (var methodInfo in methodInfoList)
+        {
+            var attributeList = Attribute.GetCustomAttributes(methodInfo, true);
 
-            if (methodInfoList == null || methodInfoList.Length == 0)
+            if (attributeList.Length == 0)
             {
-                Console.WriteLine($"The type {elementType} does not have any methods.");
-                return attributes;
+                Console.WriteLine($"The {elementType.Name}.{methodInfo.Name} method does not have attributes.");
+                continue;
             }
 
-            foreach (var methodInfo in methodInfoList)
-            {
-                var attributeList = Attribute.GetCustomAttributes(methodInfo, true);
+            Console.WriteLine($"The {elementType.Name}.{methodInfo.Name} method's attribute:");
 
-                if (attributeList.Length == 0)
-                {
-                    Console.WriteLine($"The {elementType.Name}.{methodInfo.Name} method does not have attributes.");
-                    continue;
-                }
+            foreach (var att in attributeList)
+            {
+                WriteOnTheConsole(att);
+                attributes.Add(methodInfo.Name + "-" + att.ToString());
+            }
 
-                Console.WriteLine($"The {elementType.Name}.{methodInfo.Name} method's attribute:");
+            Console.WriteLine();
+        }
 
-                foreach (var att in attributeList)
-                {
-                    WriteOnTheConsole(att);
-                    attributes.Add(methodInfo.Name + "-" + att.ToString());
-                }
+        return attributes;
+    }
 
-                Console.WriteLine();
-            }
+    public static (int FromAttributeClass, int FromMember) CountInheritedAttributes<T>(MemberInfo member)
+        where T : Attribute
+    {
+        var fromAttributeClass = Attribute.GetCustomAttributes(member, true).OfType<T>().Count();
+        var fromMember = member.GetCustomAttributes(true).OfType<T>().Count();
 
-            return attributes;
-        }
+        return (fromAttributeClass, fromMember);
     }
 }

aspnetcore-features/CustomAttributes/CustomAttributes/CustomAttributes.csproj

@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>net6.0</TargetFramework>
+    <TargetFramework>net10.0</TargetFramework>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
   </PropertyGroup>

aspnetcore-features/CustomAttributes/CustomAttributes/DeveloperTaskAttribute.cs

@@ -1,20 +1,13 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
+namespace CustomAttributes;
 
-namespace CustomAttributes
+[AttributeUsage(AttributeTargets.Method, AllowMultiple = true)]
+public class DeveloperTaskAttribute : Attribute
 {
-    [AttributeUsage(AttributeTargets.Method, AllowMultiple = true)]
-    public class DeveloperTaskAttribute : Attribute
+    public DeveloperTaskAttribute(Priorities priority)
     {
-        public DeveloperTaskAttribute(Priorities priority)
-        {
-            Priority = priority;
-        }
-
-        public Priorities Priority { get; set; }
-        public string? Description { get; set; }
+        Priority = priority;
     }
+
+    public Priorities Priority { get; set; }
+    public string? Description { get; set; }
 }

aspnetcore-features/CustomAttributes/CustomAttributes/Enums.cs

@@ -1,15 +1,8 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
+namespace CustomAttributes;
 
-namespace CustomAttributes
+public enum Priorities
 {
-    public enum Priorities
-    {
-        High,
-        Mid,
-        Low
-    }
+    High,
+    Mid,
+    Low
 }

aspnetcore-features/CustomAttributes/CustomAttributes/ManagerTaskAttribute.cs

@@ -1,15 +1,8 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
+namespace CustomAttributes;
 
-namespace CustomAttributes
+[AttributeUsage(AttributeTargets.Method, Inherited = false)]
+public class ManagerTaskAttribute : Attribute
 {
-    [AttributeUsage(AttributeTargets.Method, Inherited = false)]
-    public class ManagerTaskAttribute : Attribute
-    {
-        public Priorities Priority { get; set; }
-        public bool NeedsReport { get; set; }
-    }
+    public Priorities Priority { get; set; }
+    public bool NeedsReport { get; set; }
 }

aspnetcore-features/CustomAttributes/CustomAttributes/MyTasks.cs

@@ -1,27 +1,20 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
+namespace CustomAttributes;
 
-namespace CustomAttributes
+[TaskDescriptor(Name = "The task's name",
+    Description = "Some descriptions for the task",
+    NeedsManager = true,
+    DeveloperCount = 5)]
+public class MyTasks
 {
-    [TaskDescriptor(Name = "The task's name",
-        Description = "Some descriptions for the task",
-        NeedsManager = true,
-        DeveloperCount = 5)]
-    public class MyTasks
+    [DeveloperTask(Priorities.Low)]
+    [DeveloperTask(Priorities.High, Description = "High level description")]
+    public void ScheduleMeeting()
     {
-        [DeveloperTask(Priorities.Low)]
-        [DeveloperTask(Priorities.High, Description = "High level description")]
-        public void ScheduleMeeting()
-        {
-        }
+    }
 
-        [ManagerTask(Priority = Priorities.Mid, NeedsReport = true)]
-        [DeveloperTask(Priorities.High, Description = "High level description")]
-        public virtual void ScheduleInterview()
-        {
-        }
+    [ManagerTask(Priority = Priorities.Mid, NeedsReport = true)]
+    [DeveloperTask(Priorities.High, Description = "High level description")]
+    public virtual void ScheduleInterview()
+    {
     }
 }

aspnetcore-features/CustomAttributes/CustomAttributes/ReviewedAttribute.cs

@@ -0,0 +1,6 @@
+namespace CustomAttributes;
+
+[AttributeUsage(AttributeTargets.Method | AttributeTargets.Property)]
+public class ReviewedAttribute : Attribute
+{
+}

aspnetcore-features/CustomAttributes/CustomAttributes/TaskBoard.cs

@@ -0,0 +1,12 @@
+namespace CustomAttributes;
+
+public class TaskBoard
+{
+    [Reviewed]
+    public virtual int OpenTasks { get; set; }
+
+    [Reviewed]
+    public virtual void Archive()
+    {
+    }
+}

aspnetcore-features/CustomAttributes/CustomAttributes/TaskDescriptorAttribute.cs

@@ -1,17 +1,10 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
+namespace CustomAttributes;
 
-namespace CustomAttributes
+[AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct)]
+public class TaskDescriptorAttribute : Attribute
 {
-    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct)]
-    public class TaskDescriptorAttribute : Attribute
-    {
-        public string? Name { get; set; }
-        public string? Description { get; set; }
-        public bool NeedsManager { get; set; }
-        public int DeveloperCount { get; set; }
-    }
+    public string? Name { get; set; }
+    public string? Description { get; set; }
+    public bool NeedsManager { get; set; }
+    public int DeveloperCount { get; set; }
 }

aspnetcore-features/CustomAttributes/CustomAttributes/TeamTaskBoard.cs

@@ -0,0 +1,10 @@
+namespace CustomAttributes;
+
+public class TeamTaskBoard : TaskBoard
+{
+    public override int OpenTasks { get; set; }
+
+    public override void Archive()
+    {
+    }
+}

aspnetcore-features/CustomAttributes/CustomAttributes/YourTasks.cs

@@ -1,16 +1,9 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
+namespace CustomAttributes;
 
-namespace CustomAttributes
+public class YourTasks : MyTasks
 {
-    public class YourTasks : MyTasks
+    [DeveloperTask(Priorities.Mid, Description = "Mid level description")]
+    public override void ScheduleInterview()
     {
-        [DeveloperTask(Priorities.Mid, Description = "Mid level description")]
-        public override void ScheduleInterview()
-        {
-        }
     }
 }

aspnetcore-features/CustomAttributes/TestProject/PrintAttributesUnitTest.cs

@@ -35,5 +35,37 @@ public void WhenCorrectYourTaskInput_ThenCorrectMultipleAttOutput()
 
             Assert.IsTrue(result);
         }
+
+        [TestMethod]
+        public void WhenGenericGetCustomAttribute_ThenTypedInstanceWithoutCast()
+        {
+            var descriptor = CustomAttributeHelper.GetAttributeGeneric<TaskDescriptorAttribute>(typeof(MyTasks));
+            var missing = CustomAttributeHelper.GetAttributeGeneric<ManagerTaskAttribute>(typeof(MyTasks));
+
+            Assert.IsNotNull(descriptor);
+            Assert.AreEqual("The task's name", descriptor.Name);
+            Assert.AreEqual(5, descriptor.DeveloperCount);
+            Assert.IsNull(missing);
+        }
+
+        [TestMethod]
+        public void WhenIsDefined_ThenTrueOnlyWhereTheAttributeIsApplied()
+        {
+            Assert.IsTrue(CustomAttributeHelper.HasAttribute<TaskDescriptorAttribute>(typeof(MyTasks)));
+            Assert.IsFalse(CustomAttributeHelper.HasAttribute<ManagerTaskAttribute>(typeof(MyTasks)));
+        }
+
+        [TestMethod]
+        public void WhenInheritIsTrue_ThenMemberGetCustomAttributesIgnoresItOnPropertiesOnly()
+        {
+            var property = typeof(TeamTaskBoard).GetProperty(nameof(TeamTaskBoard.OpenTasks))!;
+            var method = typeof(TeamTaskBoard).GetMethod(nameof(TeamTaskBoard.Archive))!;
+
+            var onProperty = CustomAttributeHelper.CountInheritedAttributes<ReviewedAttribute>(property);
+            var onMethod = CustomAttributeHelper.CountInheritedAttributes<ReviewedAttribute>(method);
+
+            Assert.AreEqual((1, 0), onProperty);
+            Assert.AreEqual((1, 1), onMethod);
+        }
     }
 }