字符串加密写入文本文件(01)

该方法经过测试，并应用到项目了。

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;

namespace TBQDLKW
{
    public class FileEncryptDecrypt
    {
        /// <summary>
        /// 加密字符【长度必须为8】
        /// </summary>
        private static string _Key = "TBQDLKSW";
        /// <summary>
        /// 将密钥加密写入到文件
        /// </summary>
        /// <param name="sOutputFilename">文件路径</param>
        /// <param name="content">文件内容</param>
        /// <param name="sKey">密钥</param>
        private static void EncryptFile(string sOutputFilename, string content, string sKey)
        {
            using (FileStream fsEncrypted = new FileStream(sOutputFilename, FileMode.Create, FileAccess.Write))
            {
                using (DESCryptoServiceProvider des = new DESCryptoServiceProvider())
                {
                    des.Key = Encoding.ASCII.GetBytes(sKey);
                    des.IV = Encoding.ASCII.GetBytes(sKey);
                    ICryptoTransform desencrypt = des.CreateEncryptor();
                    using (CryptoStream cryptostream = new CryptoStream(fsEncrypted, desencrypt, CryptoStreamMode.Write))
                    {
                        byte[] fsInput = Encoding.UTF8.GetBytes(content);
                        cryptostream.Write(fsInput, 0, fsInput.Length);
                        cryptostream.Close();
                        fsEncrypted.Close();
                    }
                }
            }
        }
        /// <summary>
        /// 打开密钥文件
        /// </summary>
        private static string DecryptFile(string sInputFilename, string sKey)
        {
            using (DESCryptoServiceProvider des = new DESCryptoServiceProvider())
            {
                des.Key = Encoding.ASCII.GetBytes(sKey);
                des.IV = Encoding.ASCII.GetBytes(sKey);
                using (FileStream fsread = new System.IO.FileStream(sInputFilename, FileMode.Open, FileAccess.Read))
                {
                    ICryptoTransform desdecrypt = des.CreateDecryptor();
                    using (CryptoStream cryptostreamDecr = new CryptoStream(fsread, desdecrypt, CryptoStreamMode.Read))
                    {
                        using (StreamReader read = new StreamReader(cryptostreamDecr, Encoding.UTF8))
                        {
                            string reft = read.ReadToEnd();
                            fsread.Flush();
                            fsread.Close();
                            return reft;
                        }
                    }
                }
            }
        }
        /// <summary>
        /// 加密文件
        /// </summary>
        /// <param name="filename">文件存放路径</param>
        /// <param name="content">加密内容</param>
        public static void Encrypt(string filename, string content)
        {
            try
            {
                EncryptFile(filename, content, _Key);
            }
            catch (Exception ex)
            {
            }
        }
        /// <summary>
        /// 解密文件
        /// </summary>
        /// <param name="filename">打开文件路径</param>
        /// <returns>返回加密文件的内容</returns>
        public static bool Decrypt(string filename, out string content)
        {
            content = null;
            try
            {
                content = DecryptFile(filename, _Key);
                return true;
            }
            catch (Exception ex)
            {
                content = "文件不正确!";
                return false;
            }
        }
    }
}