Stream.Read && StreamReader.ReadToEnd

//获取请求体
using (Stream stream = Request.Body)
{
    byte[] buffer = new byte[Request.ContentLength.Value];
    stream.Read(buffer, 0, buffer.Length);
    body = Encoding.UTF8.GetString(buffer);//这么接body数据会丢失，还是偶现的，也不知道为啥，很奇怪，有知道的同学帮忙解释一下，改成下面的方式就好了

} 

using (StreamReader stream = StreamReader(request.Body)) 
{ 
    body = await stream.ReadToEndAsync(); 
}