Dynamic Assemblies

using System;
using System.Collections.Generic;
using System.Text;
using System.Xml;
using System.Reflection;

namespace DynamicAssemblyDemo
{
    public class RuleManager
    {
        List<Rule> rules = new List<Rule>();

        public List<Rule> Rules
        {
            get { return rules; }
            set { rules = value; }
        }

        Assembly assembly = null;


        public Assembly Assembly
        {
            get { return assembly; }
            set
            { 
                assembly = value;
                if(assembly != null)
                    bookShopRuleClass = Activator.CreateInstance(assembly.GetType("DynamicAssemblyDemo.DynamicAssembly.BookShopRuleClass"));
            }
        }

        object bookShopRuleClass = null;

        public void GerRulesFromTheSever()
        {
            string tempPath = "Rules.xml";
            
            XmlTextReader reader = new XmlTextReader(tempPath);
            reader.WhitespaceHandling = WhitespaceHandling.None;
            while (reader.ReadToFollowing("Rule"))
            {
                reader.ReadStartElement("Rule");
                reader.ReadStartElement("Name");
                string name = reader.ReadString();
                reader.ReadEndElement();
                reader.ReadStartElement("Item");
                string item = reader.ReadString();
                reader.ReadEndElement();
                reader.ReadStartElement("ReturnType");
                string returnType = reader.ReadString();
                reader.ReadEndElement();
                reader.ReadStartElement("Body");
                string body = reader.ReadString().Replace("And","&&");
                reader.ReadEndElement();

                Rule r = new Rule(name, body, item, returnType);
                rules.Add(r);

            }

        }

        public void SetPublicFields(string cat, string subCat, string item, double price, Int64 quanity)
        {
            Type ty = bookShopRuleClass.GetType();
            ty.GetField(Meta.price).SetValue(bookShopRuleClass, price);
            ty.GetField(Meta.quantity).SetValue(bookShopRuleClass, quanity);
            ty.GetField(Meta.subCategory).SetValue(bookShopRuleClass, subCat);
            ty.GetField(Meta.item).SetValue(bookShopRuleClass, item);

        }


        public double GetDiscount(string cat , string subCat , string item, double price , Int64 quanity)
        {
            if (bookShopRuleClass != null)
            {
                SetPublicFields(cat, subCat, item, price, quanity);
                string name = Meta.getDiscount + Meta.sep + cat;

                Type type =  bookShopRuleClass.GetType();
                MethodInfo method = type.GetMethod(name);

                if (method != null)
                {
                    object discount = method.Invoke(bookShopRuleClass, null);

                    return Convert.ToDouble(discount);
                }

            }
            return 0;
        }

        public string GetSpecialGifts(string cat, string subCat, string item, double price, Int64 quanity)
        {
            if (bookShopRuleClass != null)
            {
                SetPublicFields(cat, subCat, item, price, quanity);
                string name = Meta.getSpecialGifts + Meta.sep + cat;

                Type type = bookShopRuleClass.GetType();
                MethodInfo method = type.GetMethod(name);
                if (method != null)
                {
                    object gift = method.Invoke(bookShopRuleClass, null);

                    return gift.ToString();
                }

            }
            return string.Empty;
        }

        public bool ValidateOrderValue(string cat, string subCat, string item, double price, Int64 quanity)
        {
            if (bookShopRuleClass != null)
            {
                SetPublicFields(cat, subCat, item, price, quanity);
                string name = Meta.validateOrderValue + Meta.sep + cat;

                Type type = bookShopRuleClass.GetType();
                MethodInfo method = type.GetMethod(name);
                if (method != null)
                {
                    object ret = method.Invoke(bookShopRuleClass, null);

                    return Convert.ToBoolean(ret);
                }

            }
            return false;
        }

        public bool ValidateOrderQuantity(string cat, string subCat, string item, double price, Int64 quanity)
        {
            if (bookShopRuleClass != null)
            {
                SetPublicFields(cat, subCat, item, price, quanity);
                string name = Meta.validateOrderQuantity + Meta.sep + cat;

                Type type = bookShopRuleClass.GetType();
                MethodInfo method = type.GetMethod(name);
                if (method != null)
                {
                    object ret = method.Invoke(bookShopRuleClass, null);

                    return Convert.ToBoolean(ret);
                }

            }
            return false;
        }
    }
}