/// <summary>
        /// 获取数据库Image字段数据，保存到本地
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void button2_Click(object sender, EventArgs e)
        {
            string constr = "Data Source=IP地址服务器地址;Initial Catalog=SunS;User ID=sa;Password=1321654";
            SqlConnection con = new SqlConnection(constr);
            SqlCommand cmd = new SqlCommand();
            cmd.CommandText = "Select * from FileServer With (NoLock) Where FileName = '" + textBox1.Text + "'";
            cmd.CommandType = CommandType.Text;
            cmd.Connection = con;
            con.Open();
            DataTable dt = new DataTable();
            SqlDataAdapter ad = new SqlDataAdapter(cmd);// cmd.EndExecuteReader();
            ad.Fill(dt);
            con.Close();
            cmd.Dispose();

            byte[] pics1 = (byte[])dt.Rows[0]["CONTENT"];// 的值强制转换;
            writefile(pics1, "D://" + textBox1.Text + "");
        }

        public void writefile(byte[] pics, string filename)
        {
            FileStream fs = new FileStream(filename, FileMode.Append, FileAccess.Write);
            BinaryWriter bw = new BinaryWriter(fs);
            bw.Write(pics, 0, pics.Length);
            bw.Close();
            fs.Close();
        }
        /// <summary>
        /// 将文件转换成byte数组，写入数据库
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void button1_Click(object sender, EventArgs e)
        {
            FileInfo finfo = new FileInfo("D://" + textBox1.Text); //绝对路径
            if (finfo.Exists)
            {
                SqlConnection conn = new SqlConnection( "Data Source=IP地址服务器地址;Initial Catalog=Sun;User ID=sa;Password=1312313");
                SqlCommand InsertCommand = new SqlCommand();
                InsertCommand.Connection = conn;
                InsertCommand.CommandText = " UPDATE  FileServer SET CONTENT =@Content  WHERE [FILENAME] = '" + textBox1.Text + "'";
                InsertCommand.Parameters.Add("@Content", SqlDbType.Image, (int)finfo.Length, "CONTENT"); //注意，此处参数Size为写入的字节数
                //读取文件内容，写入byte数组
                byte[] content = new byte[finfo.Length];
                FileStream stream = finfo.OpenRead();
                stream.Read(content, 0, content.Length);
                stream.Close();
                InsertCommand.Parameters["@Content"].Value = content; //为参数赋值
                try
                {
                    conn.Open();
                    InsertCommand.ExecuteNonQuery();
                }
                finally
                {
                    conn.Close();
                }
            }
        }