//获得当前文件目录
string rootPath = Directory.GetCurrentDirectory();
string path = rootPath + "Your File Path";
FileStream stream = new FileStream(path, FileMode.Open);
//Position应该被重置为0，否则读取的时候会从最后开始读，读不出来┭┮﹏┭┮
stream.Position = 0;
MemoryStream ms = new MemoryStream();
stream.CopyTo(ms);
byte[] bytes = ms.ToArray();

string rootPath = Directory.GetCurrentDirectory();
string path = rootPath + "Your File Path";
FileStream stream = new FileStream(path, FileMode.Open);
stream.Position = 0;
byte[] bytes = new byte[stream.Length];
using (MemoryStream ms = new MemoryStream())
{
    int read;
    while ((read = stream.Read(bytes, 0, bytes.Length)) > 0)
    {
        ms.Write(bytes, 0, read);
    }
    bytes = ms.ToArray();
}