Creating and Using Attributes in your .NET application

using System;

namespace Test
{
	public class Driver
	{
		// Entry point of the program
		public static void Main(string [] Args)
		{
			// We really don't have to create an instance of TestClass*, remember
			// attributes are properties applied to Type's and the parts that make 
			// up types (fields, properties, methods, return values, parameters).
			TestClassA a = new TestClassA();
			TestClassB b = new TestClassB();
			string c = "";

			PrintTestAttributes(a);		// Should print out the number 3 and an empty string, since
										// none was specified on the class
			PrintTestAttributes(b);		// Should print out the number 4 and the name of the class
			PrintTestAttributes(c);		// Shouldn't print out that TestAttribute exists
		}
		
		// Prints out the values for the TestAttribute on the object
		// if the TestAttribute isn't applied it prints out a message
		// indicating such
		public static void PrintTestAttributes(object obj)
		{
			Type type = obj.GetType();	// Get the underlying type from the object passed in
										// attributes are decorations on Type's so we need
										// a Type object to operate on.

			// Get the attributes applied to this object of type
			// TestAttribute, this returns an array of TestAttributes, one for 
			// each TestAttribute applied to the class.
			// The code will only expect 0 or 1 TestAttributes to be applied
			// The false parameter tells the runtime to only search this type, none of the base types for the attribute
			TestAttribute [] AttributeArray = (TestAttribute []) type.GetCustomAttributes(typeof(TestAttribute), false);
			
			// Class name
			Console.WriteLine("Class:\t{0}", type.Name);

			// If no attributes were returned, print out the message
			if( AttributeArray.Length == 0 )
			{
				Console.WriteLine("There are no TestAttributes applied to this class");
				return ;
			}

			// Retrieve the one and only instance of TestAttribute from class
			TestAttribute ta = AttributeArray[0];
			
			// Called the TestAttribute's PrintOut method
			ta.PrintOut();
		}
	}
}