AOP using System.Reflection.Emit - Code Injection IL

using System;
using System.Reflection;
using System.Collections;
using System.Collections.Specialized;
using System.Data;
using System.IO;
using System.Threading;

namespace SadasSof.Aspects.Attributes
{
	[AttributeUsage(AttributeTargets.Method | AttributeTargets.Property |
	 AttributeTargets.Interface ,Inherited=true)]
	public abstract  class AspectAttribute : Attribute
	{
		public abstract object Action(object target, MethodBase method, object[] parameters, object result);
	}

	public abstract class BeforeAttribute: AspectAttribute
	{
	}

	public abstract class AfterAttribute: AspectAttribute
	{
	}

	public abstract class LogExceptionAttribute: AspectAttribute
	{
	}


	public class LoggerExceptionToFile:LogExceptionAttribute
	{
		string pathInternal = @"c:\logException.txt";

		public LoggerExceptionToFile(string path)
		{
			pathInternal = path;
			
		}

		public LoggerExceptionToFile()
		{	
		}

		public override object Action(object target, MethodBase method, object[] parameters, object result)
		{
			string namePrincipal = Thread.CurrentPrincipal.Identity.Name;
			if(namePrincipal==string.Empty)
				namePrincipal="Anonymous User";

			namePrincipal="User: " + namePrincipal;

			string text = "Assambly: " + target.ToString() +
			"\nMethod: " + method.Name+
			"\n\nInnerException: " + ((Exception)result).InnerException;

			string content = SadasSof.Aspects.Helper.ReadFile(pathInternal);
			
			try
			{
				SadasSof.Aspects.Helper.SaveToFile(namePrincipal, text,content, pathInternal);
			}
			catch
			{
				throw;
			}

			return null;
		}
	}


	public class LoggerToFile:BeforeAttribute
	{
		string pathInternal = @"c:\log.txt";

		public LoggerToFile(string path)
		{
			pathInternal = path;
			
		}

		public LoggerToFile()
		{	
		}

		public override object Action(object target, MethodBase method, object[] parameters, object result)
		{
			string namePrincipal = Thread.CurrentPrincipal.Identity.Name;
			if(namePrincipal==string.Empty)
					namePrincipal="Anonymous User";

			namePrincipal="User: " + namePrincipal;

			string text = "Assambly: " + target.ToString() +"\nMethod: " + method.Name;

			string content = SadasSof.Aspects.Helper.ReadFile(pathInternal);
			
			try
			{
				SadasSof.Aspects.Helper.SaveToFile(namePrincipal, text,content, pathInternal);
			}
			catch
			{
				throw;
			}

			return null;
		}
	}


	public class CountingCalls:BeforeAttribute
	{
		static Hashtable calls;

		public override object Action(object target, MethodBase method, object[] parameters, object result)
		{
			if(calls==null)
				calls=new Hashtable();

			if(calls[method.Name]==null)
				calls[method.Name]=1;
			else
				calls[method.Name]=((int)calls[method.Name])+1;

			return null;

		}

		public static int Calls(string methodName)
		{
			
				if(calls==null ||calls[methodName]==null)
					return 0;
				else 
					return (int)calls[methodName];
			   
		}
	}


	public class ExternalFilter:AfterAttribute
	{

		public override object Action(object target, MethodBase method, object[] parameters, object result)
		{
		
			DataRowCollection drC= ((DataSet)result).Tables[0].Rows;
		

			for(int i=0;i<drC.Count;i++)
			{
				if(!(bool)drC[i]["External"])
				{
					drC[i].Delete();
					i--;
				}
			}
			
			 ((DataSet)result).AcceptChanges();

			return result;

		}


		

	}




}