读文件时，怎么判断文件是否结尾呢？

Question

private void button4_Click(object sender, RoutedEventArgs e)
        {
            if (openFile.ShowDialog() == true)
            {               
                openFile.File.OpenRead();            }
            if (openFile.File != null)
            {
                filname = "123.txt";
                WebClient webclient = new WebClient();                Uri uri = new Uri("http://192.1.2.3:80/ReaderClientTestPage.html?filename+" + filname, UriKind.Absolute);
                webclient.OpenWriteCompleted += new OpenWriteCompletedEventHandler(webclient_OpenWriteCompleted);
                webclient.OpenWriteAsync(uri, "POST", openFile.File.OpenRead());
            }
            else
            {
                // MessageBox.Show("请先选择文件！");
            }
        }
        void webclient_OpenWriteCompleted(object sender,OpenWriteCompletedEventArgs e)
        {
            Stream inputStream = e.UserState as Stream;
            Stream outputStream = e.Result;
            byte[] buffer = new byte[1024];
            int bytesRead = 0;          
            bytesRead = inputStream.Read(buffer, 0, 2); 
            bytesRead = inputStream.Read(buffer, 0, 2);
            bytesRead = inputStream.Read(buffer, 0, 2);
            bytesRead = inputStream.Read(buffer, 0, 2);
}在按钮里，打开文件，，然后触发事件---webclient_OpenWriteCompleted（）
在这里做文件读操作            bytesRead = inputStream.Read(buffer, 0, 2);   一次读文件中2个字节（测试写固定内容:ABCDEFGH）
   共四句
   第一次读到了 AB
   第二次：CD
  第三次：EF
  第四次：GH
   只要文件流不关闭，每次都会从上次结束的地方，作为新一次读的开始，  但现在，想判断文件的结束，，怎么弄呢？
  像C 里的
   if(!feof(fptr))
   这样的
    就是把   bytesRead = inputStream.Read(buffer, 0, 2); 整成一句，，在一个判断里，只要文件没有读完，就继续读
每次读到长度相同谢谢  

Answer 1

var buffer = new Byte[1024];
var offset = 0;
var len = 0;
using (var fs = File.OpenWrite(filename))
{
    while ((len = stream.Read(buffer, 0, buffer.Length)) > 0)
    {
        fs.Write(buffer, 0, len);
        offset += len;
    }
}
只要 Read 返回的 length == 0 就说明读完了。

Answer 2

while((bytesRead = inputStream.Read(buffer, 0, 2))>=0)
{
  //...
}