Inconsistent accessibility: property type is less accessible

make your class public access modifier,

just add public keyword infront of your class name

 namespace Test
{
  public  class Delivery
    {
        private string name;
        private string address;
        private DateTime arrivalTime;

        public string Name
        {
            get { return name; }
            set { name = value; }
        }

        public string Address
        {
            get { return address; }
            set { address = value; }
        }

        public DateTime ArrivlaTime
        {
            get { return arrivalTime; }
            set { arrivalTime = value; }
        }

        public string ToString()
        {
            { return name + address + arrivalTime.ToString(); }
        }
    }
}

Your Delivery class is internal (the default visibility for classes), however the property (and presumably the containing class) are public, so the property is more accessible than the Delivery class. You need to either make Delivery public, or restrict the visibility of the thelivery property.

Your class Delivery has no access modifier, which means it defaults to internal. If you then try to expose a property of that type as public, it won't work. Your type (class) needs to have the same, or higher access as your property.

More about access modifiers: http://msdn.microsoft.com/en-us/library/ms173121.aspx