判断网络文件是否存在，获取网络文件大小，创建时间、修改时间

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Text;

namespace Sci
{
    /// <summary>
    /// 网络文件处理工具
    /// </summary>
    class WebFile
    {
        /// <summary>
        /// 判断网络文件是否存在
        /// </summary>
        /// <param name="url"></param>
        public static bool fileExist(string url)
        {
            return getFileLen(url) != -1;
        }

        /// <summary>
        /// 获取网络文件大小
        /// </summary>
        /// <param name="url">文件网址</param>
        /// <returns></returns>
        public static long getFileLen(string url)
        {
            try
            {
                WebRequest request = WebRequest.Create(url);
                request.Timeout = 200;
                WebResponse response = request.GetResponse();

                return response.ContentLength;  // 文件大小
                //return response.ContentType;  // 文件类型
            }
            catch (Exception)
            {
                return -1;  // 文件不存在
            }
        }

        /// [Accept-Ranges, bytes]
        /// [Content-Length, 13927]
        /// [Content-Type, application/x-zip-compressed]
        /// [Date, 2022-05-28 12:32:59]
        /// [ETag, "9258b93b05ed81:0"]
        /// [Last-Modified, 2022-05-02 16:40:10]
        /// [Server, Microsoft-IIS/8.5]
        /// [X-Powered-By, ASP.NET]

        /// <summary>
        /// 获取网络文件属性信息，如：getFileInfo(url)["Last-Modified"];
        /// </summary>
        /// <param name="url">文件网址</param>
        /// <returns></returns>
        public static Dictionary<string, string> getFileInfo(string url)
        {
            Dictionary<string, string> dic = new Dictionary<string, string>();
            try
            {
                WebRequest request = WebRequest.Create(url);
                request.Timeout = 200;
                WebResponse response = request.GetResponse();

                WebHeaderCollection col = response.Headers;
                foreach (string key in col.Keys)
                {
                    string value = col.Get(key);
                    if (value.EndsWith(" GMT")) value = DateTime.Parse(value).ToString("yyyy-MM-dd HH:mm:ss");
                    if (!dic.ContainsKey(key)) dic.Add(key, value);
                }
            }
            catch (Exception)
            {
            }
            return dic;
        }

    }
}