/// <summary>
    /// 提供上传文件时所使用的方法
    /// </summary>
    public interface IUploadFile
    {
        /// <summary>
        /// 验证上传文件的扩展名
        /// </summary>
        /// <param name="postFile">System.Web.HttpPostedFile对象</param>
        /// <returns></returns>
        bool CheckFileType(System.Web.HttpPostedFile postFile);

        /// <summary>
        /// 获取文件名称
        /// 调用此方法并不创建新目录
        /// </summary>
        /// <param name="filePath">服务器的虚拟路径</param>
        /// <param name="fileName">文件名</param>
        /// <returns></returns>
        string GetFileName(string filePath,string fileName);
    }

 /// <summary>
    /// 提供上传文件时所使用的方法
    /// </summary>
    public abstract class UploadFile
    {        
        /// <summary>
        /// 获取文件路径
        /// </summary>
        /// <param name="path">虚拟路径</param>
        /// <returns></returns>
        protected string GetDirectory(string path)
        {
            string directoryName = DateTime.Now.ToString("yyyyMMdd");
            string filePath = Path.Combine(path, directoryName);
            if (!Directory.Exists(filePath))
            {
                return Path.Combine(filePath, GetNumber(1));
            }
            return Path.Combine(filePath, GetPath(Directory.GetDirectories(filePath), filePath));
        }

        /// <summary>
        /// 获取文件夹中的文个数件少于1000的文件夹名称
        /// </summary>
        /// <param name="info">目录名称</param>
        /// <param name="filePath">路径</param>
        /// <returns></returns>
        protected string GetPath(IList<string> info, string filePath)
        {
            string fileName = string.Empty;

            if (info == null)
            {
                return null;
            }
            if (info.Count <= 0)
            {
                return GetNumber(1);
            }
            for (int i = 0; i < info.Count; i++)
            {
                if (Directory.Exists(info[i]))
                {
                    if (Directory.GetFiles(info[i]).Length < 1000)
                    {
                        fileName = info[i];
                        break;
                    }
                }
            }
            if (string.IsNullOrEmpty(fileName))
            {
                return Path.Combine(filePath, GetNumber(int.Parse(info.ToList<string>().Max(s => s.Substring(s.LastIndexOf("\\") + 1).TrimStart('0'))) + 1));
            }
            else
            {
                return fileName;
            }
        }

        /// <summary>
        /// 获取数字字符串，不足4位用0补足
        /// </summary>
        /// <param name="number">不大于9999的数字</param>
        /// <returns></returns>
        protected string GetNumber(int number)
        {
            if (number > 9999) return null;
            return (10000 + number).ToString().Substring(1);
        }
        

        #region IUploadFile 成员

        /// <summary>
        /// 验证上传文件的扩展名
        /// </summary>
        /// <param name="postFile">System.Web.HttpPostedFile对象</param>
        /// <returns></returns>
        public abstract bool CheckFileType(System.Web.HttpPostedFile postFile);

        /// <summary>
        /// 获取文件名称
        /// </summary>
        /// <param name="filePath">服务器的虚拟路径</param>
        /// <param name="fileName">文件名</param>
        /// <returns></returns>
        public virtual string GetFileName(string filePath,string fileName)
        {
            DateTime now = DateTime.Now;
            string name = (100 + now.Hour).ToString().Substring(1) + (100 + now.Minute).ToString().Substring(1) + (100 + now.Second).ToString().Substring(1) + "_" + fileName;
            return Path.Combine(GetDirectory(filePath), name);
        }

        #endregion
    }

public class LBCUploadFile:UploadFile,IUploadFile
    {
        /// <summary>
        /// 验证上传文件的扩展名
        /// </summary>
        /// <param name="postFile">System.Web.HttpPostedFile对象</param>
        /// <returns></returns>
        public override bool CheckFileType(System.Web.HttpPostedFile postFile)
        {
            IList<string> fileType = new List<string>();
            fileType.Add("image/gif");
            fileType.Add("image/jpeg");
            fileType.Add("image/png");
            return fileType.Contains(postFile.ContentType);
        }
    }