using System;
using System.IO;
using System.Text;
using System.Text.RegularExpressions;
using System.Runtime.Remoting;
using System.Runtime.Remoting.Proxies;
using System.Runtime.Remoting.Messaging;
using System.Reflection;
namespace FilterRealProxy
{
/**//**//**//// <summary>
///  FilterRealProxy类：一个真实代理, 拦截它所代理对象中方法的返回值，并对需要过滤的返回值进行过滤。
/// </summary>
 public class FilterRealProxy:RealProxy
{
private MarshalByRefObject target;
public FilterRealProxy(MarshalByRefObject target):base(target.GetType())
{
this.target=target;
}
public override IMessage Invoke(IMessage msg)
{
IMethodCallMessage callMsg=msg as IMethodCallMessage;
IMethodReturnMessage returnMsg = RemotingServices.ExecuteMessage(target,callMsg);
//检查返回值是否为String,如果不是String,就没必要进行过滤
   if(this.IsMatchType(returnMsg.ReturnValue))
{
string returnValue=this.Filter(returnMsg.ReturnValue.ToString(),returnMsg.MethodName);
return new ReturnMessage(returnValue,null,0,null,callMsg);
}
return returnMsg;
　　　　 }
protected string Filter(string ReturnValue,string MethodName)
{
MethodInfo methodInfo=target.GetType().GetMethod(MethodName);
object[] attributes=methodInfo.GetCustomAttributes(typeof(StringFilter),true);
foreach (object attrib in attributes)
{
return FilterHandler.Process(((StringFilter)attrib).FilterType,ReturnValue);
}
return ReturnValue;
}
protected bool IsMatchType(object obj)
{
return obj is System.String;
}
}
/**//**//**////<summary>
///  StringFilter类：自定义属性类, 定义目标元素的过滤类型
///</summary>
 public class StringFilter:Attribute
{
protected FilterType _filterType;
public StringFilter(FilterType filterType)
{
this._filterType=filterType;
}
public FilterType FilterType
{
get
{
return _filterType;
}
}
}
/**//**//**//// <summary>
/// 枚举类：用于指定过滤类型，例如：对script过滤还是对html进行过滤？
/// </summary>
 [Flags()]
public enum FilterType
{
Script = 1,
Html =2,
Object=3,
AHrefScript=4,
Iframe=5,
Frameset=6,
Src=7,
BadWords=8,
//Include=9,
  All=16
}
/**//**//**////<summary>
/// 过滤处理类：根据过滤类型，调用相应的过滤处理方法。
///</summary>

public class FilterHandler
{
private FilterHandler()
{
}
public static string Process(FilterType filterType,string filterContent)
{
switch(filterType)
{
case FilterType.Script:
filterContent=FilterScript(filterContent);
break;
case FilterType.Html:
filterContent=FilterHtml(filterContent);
break;
case FilterType.Object:
filterContent=FilterObject(filterContent);
break;
case FilterType.AHrefScript:
filterContent=FilterAHrefScript(filterContent);
break;
case FilterType.Iframe:
filterContent=FilterIframe(filterContent);
break;
case FilterType.Frameset:
filterContent=FilterFrameset(filterContent);
break;
case FilterType.Src:
filterContent=FilterSrc(filterContent);
break;
//case FilterType.Include:
// filterContent=FilterInclude(filterContent);
// break;
    case FilterType.BadWords:
filterContent=FilterBadWords(filterContent);
break;
case FilterType.All:
filterContent=FilterAll(filterContent);
break;
default:
//do nothing
     break;
}
return filterContent;
}