Question

public void fileReader()
{
Stream stream = new FileStream(filename, FileMode.Open , FileAccess.Read , FileShare.None, 30, true);
byte[] Buffer = new byte[30];
while (stream.Read(Buffer, 0, 30) > 0)
{ 
 label1.text=Encoding.UTF8.GetString(Buffer); 
 Thread.Sleep(1000);
}
stream.Dispose();
}

THIS IS MY C# CODE TO READ 30 BYTES OF DATA AT A TIME FROM A FILE. I’ve created the Stream with FileStream constructor having useAsync=true. Here stream.Read method is used.

1. Is this read operation working in ASYNCHRNOUS mode?

2. How to check this?

3. Another problem is that Encoding.UTF8.GetString(Buffer); gives white spaces as ‘□’ character… y?

4. Is there any other way to make a 1 second delay other than Thread.Sleep(1000); ?

Answer 1

It doesn’t since you are using the syncronous Readmethod

if you wish to read it asyncronous you would have to use the BeginRead method

Below is an example on the usage of BeginRead from MSDN

private void ReadStreamAsyncImpl(Stream stream)
    {
        chunk = new byte[chunkSize];
        stream.BeginRead(chunk, 
                         0, 
                         chunkSize, 
                         new AsyncCallback(BeginReadCallback), 
                         stream);
    }

    private void BeginReadCallback(IAsyncResult ar)
    {
        Stream stream = ar.AsyncState as Stream;
        int bytesRead = stream.EndRead(ar);
        StreamContentsAsString += StreamEncoding.GetString(chunk, 0, bytesRead);

        if (bytesRead < chunkSize) {
            // Finished
            isOperationInProgress = false;
            stream.Close();
            if (null != ReadStreamCompleted) {
                ReadStreamCompleted(this, new EventArgs());
            }
        } else {
            ReadStreamAsyncImpl(stream);
        }
    }

That said you should probably use a StreamReader to read the characters of the stream instead of converting them yourself.

if you are using .NET 4.5 you can use ReadAsync as below (again from [MSDN][2])

private async void Button_Click(object sender, RoutedEventArgs e)
{
UnicodeEncoding uniencoding = new UnicodeEncoding();
string filename = @”c:\Users\exampleuser\Documents\userinputlog.txt”;
byte[] result;

        using (FileStream SourceStream = File.Open(filename, FileMode.Open))
        {
            result = new byte[SourceStream.Length];
            await SourceStream.ReadAsync(result, 0, (int)SourceStream.Length);
        }

        UserInput.Text = uniencoding.GetString(result);
    }