ExtensionApplicationAttribute
This attribute is used to specify the Type of class that implements
            IExtensionApplication interface in the specified assembly. This 
            attribute can be used only once at assembly level. Having this attribute
            saves the cost of reflection on each exported types to find the type
            that implements IExtensionApplication interface.
            
using System;
namespace Autodesk.DesignScript.Runtime
{
    [AttributeUsage(AttributeTargets.Assembly, AllowMultiple = false, Inherited = false)]
    internal sealed class ExtensionApplicationAttribute : Attribute
    {
        public Type Type { get; set; }
        public ExtensionApplicationAttribute(Type entryPointType)
        {
            Type = entryPointType;
        }
    }
}
            