Sharepoint 列表ItemAdding事件判断文件类型、获取当前上传的文件

using System;
using System.Security.Permissions;
using Microsoft.SharePoint;
using Microsoft.SharePoint.Security;
using Microsoft.SharePoint.Utilities;
using Microsoft.SharePoint.Workflow;
using System.Web;
using System.IO;

namespace TestSharePointProject.DocEvent
{
    /// <summary>
    /// List Item Events
    /// </summary>
    public class DocEvent : SPItemEventReceiver
    {
        HttpContext currentContext;
        public DocEvent()
        {
            currentContext = HttpContext.Current;
        }

       /// <summary>
       /// An item is being added.
       /// </summary>
        public override void ItemAdding(SPItemEventProperties properties)
        {
            //将上载的文件URL按.分为两部分:URL和文件类型
            string[] fileUrl = properties.BeforeUrl.Split('.');
            if (fileUrl.Length == 1)
            {
                properties.ErrorMessage = "文件类型不合法！";
                properties.Cancel = true;
            }
            else
            {
                //获取上载的文件类型
                string postFix = fileUrl[fileUrl.Length - 1].ToLower();
                if (!postFix.Contains("xlsx") && !postFix.Contains("xls"))
                {
                    properties.ErrorMessage = "请选择上传Excel文件！";
                    properties.Cancel = true;
                }
                else {
                    if (currentContext != null)
                    {
                        if (currentContext.Request.Files.Count > 0)
                        {
                            //获取Item中被上传的所有文件
                            for (int i = 0; i < currentContext.Request.Files.Count; i++)
                            {
                                if (!string.IsNullOrEmpty(currentContext.Request.Files[i].FileName))
                                {
                                    FileStream file = null;
                                    string path = currentContext.Request.Files[i].FileName.ToString();

                                    // Read the file. This appears to be the offending line
                                    file = File.OpenRead(path);
                                    byte[] Content = new byte[file.Length];
                                    file.Read(Content, 0, (int)file.Length);
                                    file.Close();
                                    file.Dispose();
                                    //itemToAdd.Attachments.Add(currentContext.Request.Files[i].FileName, Content);
                                }
                            }
                        }
                    }
                }
            }
        }

       /// <summary>
       /// An item is being updated.
       /// </summary>
       public override void ItemUpdating(SPItemEventProperties properties)
       {
           base.ItemUpdating(properties);
       }

    }
}