Type, MethodInfo, activation, custom attributes
Get Type objects, locate MethodInfo, invoke methods, create instances with Activator, and define/read custom attributes.
Type, MethodInfo, activation, custom attributes is a free C# Academy lesson on CoddyKit — lesson 1 of 3. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the C# Academy learning path, one of 3 lessons in the course, and your progress syncs across the web and the CoddyKit app.
Overview
Goal: Use reflection safely.
- Get Type
- Find MethodInfo
- Create via Activator
- Define & read attributes
Get Type
Get Type from typeof, an instance with GetType(), or by name via Type.GetType.
using System;
public class Sample { }
public class Program
{
public static void Main(string[] args)
{
// 1) From a compile-time type
Type t1 = typeof(Sample);
// 2) From an instance
Sample s = new Sample();
Type t2 = s.GetType();
// 3) From a full name (needs assembly-qualified name for external types)
Type t3 = Type.GetType("System.String");
Console.WriteLine(t1.Name + ", " + t2.FullName + ", " + (t3 == null ? "null" : t3.Name));
}
}
MethodInfo.Invoke
Use GetMethod to locate a method and Invoke to call it. Pass instance and argument array.
using System;
using System.Reflection;
public class Greeter
{
public string Hello(string name) { return "Hello, " + name; }
}
public class Program
{
public static void Main(string[] args)
{
Greeter g = new Greeter();
Type t = typeof(Greeter);
MethodInfo mi = t.GetMethod("Hello"); // public instance method
object result = mi.Invoke(g, new object[] { "Ada" }); // call dynamically
Console.WriteLine(result); // Hello, Ada
}
}
Activator basics
Activator.CreateInstance(Type) constructs an object using the public parameterless constructor.
using System;
public class Person
{
public string Name { get; set; }
public Person() { Name = "Unknown"; } // parameterless ctor
}
public class Program
{
public static void Main(string[] args)
{
Type tp = typeof(Person);
object o = Activator.CreateInstance(tp); // uses public parameterless ctor
Person p = (Person)o;
p.Name = "Alan";
Console.WriteLine("Created: " + p.Name);
}
}
Custom attributes
Create a small Attribute class and retrieve it via GetCustomAttributes on the type or method.
using System;
using System.Reflection;
[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method)]
public sealed class LabelAttribute : Attribute
{
public string Text { get; private set; }
public LabelAttribute(string text) { Text = text; }
}
[Label("Utility class")]
public class Utils
{
[Label("Adds two ints")]
public static int Add(int a, int b) { return a + b; }
}
public class Program
{
public static void Main(string[] args)
{
Type t = typeof(Utils);
// Read class attribute
object[] classAttrs = t.GetCustomAttributes(typeof(LabelAttribute), false);
if (classAttrs.Length > 0)
Console.WriteLine("Class label: " + ((LabelAttribute)classAttrs[0]).Text);
// Read method attribute
MethodInfo mi = t.GetMethod("Add");
object[] methodAttrs = mi.GetCustomAttributes(typeof(LabelAttribute), false);
if (methodAttrs.Length > 0)
Console.WriteLine("Method label: " + ((LabelAttribute)methodAttrs[0]).Text);
}
}
Tips & safety
Tips:
- Check for null from Type.GetType and missing members.
- Prefer typeof when possible (faster, safer).
- Keep reflection usage centralized and well-documented.
- Use BindingFlags for non-public or static lookups.
Activation basics
Recap
Recap: Get a Type, find MethodInfo, create with Activator, and read attributes using GetCustomAttributes.
Frequently asked questions
Is the “Type, MethodInfo, activation, custom attributes” lesson free?
Yes — the full text of “Type, MethodInfo, activation, custom attributes” is free to read here on the web, and the C# Academy course includes 3 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the C# Academy course, upgrade to CoddyKit PRO.
What will I learn in “Type, MethodInfo, activation, custom attributes”?
Get Type objects, locate MethodInfo, invoke methods, create instances with Activator, and define/read custom attributes. You practise C# Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start C# Academy?
No prior experience is required. C# Academy on CoddyKit is structured for beginners through advanced learners; this is — lesson 1 of 3, so you can start here or from the beginning and move at your own pace.
How long does the “Type, MethodInfo, activation, custom attributes” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this C# Academy lesson?
Yes. Every C# Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- Type, MethodInfo, activation, custom attributes
- Source-level info (Caller attributes)
- Light metaprogramming scenarios