hi, thanks Sebastiaan, just for future reading of other readers, I just put the my solution code below:

=====================================================================================

using System.IO;
using umbraco.BusinessLogic;
using umbraco.cms.businesslogic.media;

namespace Sanitarium.VegeToolkit.Common
{
    public class uevent:ApplicationBase
    {
        public uevent()
        {
            Media.BeforeSave += new Media.SaveEventHandler(Media_BeforeSave);
            Media.AfterSave += new Media.SaveEventHandler(Media_AfterSave);
        }

        void Media_AfterSave(Media sender, umbraco.cms.businesslogic.SaveEventArgs e)
        {
            throw new Exception("The method or operation is not implemented.");
        }       

        void Media_BeforeSave(Media sender, umbraco.cms.businesslogic.SaveEventArgs e)
        {
            //throw new Exception("The method or operation is not implemented.");           
            Media media=sender as Media; //get uploaded media file
            string file_location = media.getProperty("umbracoFile").Value.ToString(); //get uploaded file location
            string file_extension = media.getProperty("umbracoExtension").Value.ToString(); //get uploaded file extension
            string file_path = Path.Combine(umbraco.GlobalSettings.FullpathToRoot, file_location.Substring(1)); //get the uploaded file physical location
            if (!file_extension.Equals("pdf") && System.IO.File.Exists(file_path)) //if extension is not "pdf" and uploaded file exists
            {
                System.IO.File.Delete(file_path);
                media.getProperty("umbracoFile").Value = string.Empty;
            }
        }
    }
}

========================================================================================

it seems before calling "BeforeSave" event, the file already be uploaded, if I uncomments the "throw new exception..." in "Media_BeforeSave" function, I got the system error shows "BeforeSave" has been called after media "Save" call, don't know why, it doesn't make sense.

Also, when I run the code the "AfterSave" event never be called, is it a bug?

Zip, how did you resolve this issue?

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