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

namespace ConsoleApp18
{
    class Program
    {
        static void Main(string[] args)
        {
            string base64Str = FileToBase64Str("D:\\001.txt");
            Console.WriteLine();
        }

        /// <summary>
        /// 將指定文件轉(zhuǎn)換成Base64字符串
        /// </summary>
        /// <param name="path">文件路徑</param>
        /// <returns>返回Base64字符串</returns>
        public static string FileToBase64Str(string path)
        {
            // 空路徑名是不合法的
            if (string.IsNullOrEmpty(path))
            {
                throw new ArgumentException("Empty path name is not legal.", "path");
            }

            // 判斷路徑是否存在
            if (!File.Exists(path))
            {
                throw new FileNotFoundException("Could not find file '" + path + "'.", path);
            }

            string base64Str;
            using (System.IO.FileStream fileStream = new System.IO.FileStream(path, System.IO.FileMode.Open, System.IO.FileAccess.Read))
            {
                byte[] bt = new byte[fileStream.Length];
                // 調(diào)用read讀取方法  
                fileStream.Read(bt, 0, bt.Length);
                base64Str = Convert.ToBase64String(bt);
            }

            return base64Str;
        }
    }
}