In writing mode, the number of bytes that can currently be written via Write() or WriteByte() without blocking. In reading mode, returns the number of bytes that can currently be read via Read() or ReadByte() without blocking or -1 if the end of the stream has been reached. This property is read-only.

public virtual int Available { get; }

Public Overridable ReadOnly Property Available As Integer

public:
virtual property int Available {
	int get ();
}

AsyncStream asyncStream = new AsyncStream(File.OpenRead(@"C:\somefile.txt"),10);
//...do something...
byte[] myBuffer = new byte[10];
int read = 0;
if (asyncStream.Available > 0)
    read = asyncStream.Read(myBuffer,0,asyncStream.Available); //will not block
//...do something else...
asyncStream.Close(); //cleanup