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.