Reading an attribute

Method GetCustomAttributes returns an array of custom attributes applied to the member. After retrieving this array you can search for one or more specific attributes.

var attribute = typeof(MyClass).GetCustomAttributes().OfType<MyCustomAttribute>().Single();

Or iterate through them

foreach(var attribute in typeof(MyClass).GetCustomAttributes()) {
    Console.WriteLine(attribute.GetType());
}

GetCustomAttribute extension method from System.Reflection.CustomAttributeExtensions retrieves a custom attribute of a specified type, it can be applied to any MemberInfo.

var attribute = (MyCustomAttribute) typeof(MyClass).GetCustomAttribute(typeof(MyCustomAttribute));

GetCustomAttribute also has generic signature to specify type of attribute to search for.

var attribute = typeof(MyClass).GetCustomAttribute<MyCustomAttribute>();

Boolean argument inherit can be passed to both of those methods. If this value set to true the ancestors of element would be also to inspected.