将文件转换成二进制方法：

     /// <summary>
    /// 将文件转换成二进制
    /// </summary>
    /// <param name="Path">文件路径</param>
    /// <returns></returns>
    public static byte[] ConvertToBinary(string Path)
    {
        FileStream stream = new FileInfo(Path).OpenRead();
        byte[] buffer = new byte[stream.Length];
        stream.Read(buffer, 0, Convert.ToInt32(stream.Length));
        return buffer;
    }



将二进制转换成文件方法：
using System.IO;

string filePath = "D:\\a.jpg";   //文件路径
byte[] br = ConvertToBinary(filePath);
FileStream fstream = File.Create(filePath, br.Length);
try
{  
     fstream.Write(br, 0, br.Length);   //二进制转换成文件
}
catch(Exception ex)
{
     //抛出异常信息
}
 finally
{
     fstream.Close();    
}

附加：二进制与图片互转

Image aa=newBitmap(@"E:\photo\tm.jpg");     
System.IO.MemoryStream stream=newSystem.IO.MemoryStream();      
System.Runtime.Serialization.Formatters.Binary.BinaryFormatter formatter=new System.Runtime.Serialization.Formatters.Binary.BinaryFormatter();
formatter.Serialize(stream, aa);//将图像序列化成二进制流             
stream.Position=0;             
Image bb=(Image)formatter.Deserialize(stream); //将二进制流序列成Image

实际用法：目的：把jar包或者zip包（也可以过滤其他类型文件）保存到数据库里面。

private void UploadFile()
        {
            OpenFileDialog dialog = new OpenFileDialog();
            dialog.Filter = "压缩文件|*.zip;*.jar";//文件扩展名(当然这里也可以过滤其他文件)
            dialog.CheckFileExists = true;
            dialog.ShowDialog();
            if (!string.IsNullOrEmpty(dialog.FileName))//可以上传压缩包.zip 或者jar包
            {
                try
                {
                    byte[] byteArray = FileBinaryConvertHelper.File2Bytes(dialog.FileName);//文件转成byte二进制数组
                    string JarContent = Convert.ToBase64String(byteArray);//将二进制转成string类型，可以存到数据库里面了                                   
                }
                catch (Exception ex)
                {
                    MessageBox.Show(ex.Message);
                }
            }
        }

工具类：
/// <summary>
    /// 工具类：文件与二进制流间的转换
    /// </summary>
    public class FileBinaryConvertHelper
    {
        /// <summary>
        /// 将文件转换为byte数组
        /// </summary>
        /// <param name="path">文件地址</param>
        /// <returns>转换后的byte数组</returns>
        public static byte[] File2Bytes(string path)
        {
            if (!System.IO.File.Exists(path))
            {
                return new byte[0];
            }


            FileInfo fi = new FileInfo(path);
            byte[] buff = new byte[fi.Length];


            FileStream fs = fi.OpenRead();
            fs.Read(buff, 0, Convert.ToInt32(fs.Length));
            fs.Close();


            return buff;
        }


        /// <summary>
        /// 将byte数组转换为文件并保存到指定地址
        /// </summary>
        /// <param name="buff">byte数组</param>
        /// <param name="savepath">保存地址</param>
        public static void Bytes2File(byte[] buff, string savepath)
        {
            if (System.IO.File.Exists(savepath))
            {
                System.IO.File.Delete(savepath);
            }


            FileStream fs = new FileStream(savepath, FileMode.CreateNew);
            BinaryWriter bw = new BinaryWriter(fs);
            bw.Write(buff, 0, buff.Length);
            bw.Close();
            fs.Close();
        }
    }