Stream.CopyTo(newStream) return Length 0 - audio

Question

I try to make some concatenation of buffers which are saved in a memory streams. Then, when I'm trying to play the whole buffer it gives an exception:
An exception of type 'System.ArgumentException' occurred in
Microsoft.Xna.Framework.ni.dll but was not handled in user code
Additional information: Ensure that the buffer length is non-zero and
meets the block alignment requirements for the audio format.
When I debug the mStrm is still remains 0, can't find why.
private void mySendClick(object sender, RoutedEventArgs e)
{
var mStrmStartDelimiter = new MemoryStream();
var mStrmEndDelimiter = new MemoryStream();
BinaryWriter writer1 = new BinaryWriter(mStrmStartDelimiter);
Sinus(6500, 200, writer1, 32767);
BinaryWriter writer2 = new BinaryWriter(mStrmEndDelimiter);
Sinus(6800, 200, writer2, 32767);
var mStrm = new MemoryStream();
mStrmStartDelimiter.CopyTo(mStrm);
//ToDO
mStrmEndDelimiter.CopyTo(mStrm);
mStrm.Seek(0, SeekOrigin.Begin);
SoundEffect mySoundPlay = new SoundEffect(mStrm.ToArray(), 16000, AudioChannels.Mono);
mySoundPlay.Play();
}
public static void Sinus(double frequency, int msDuration, BinaryWriter writer, int volume)
{
double TAU = 2 * Math.PI;
double samplesPerSecond = 16000;
double theta = frequency * TAU / (double)samplesPerSecond;
int samples = (int)((decimal)samplesPerSecond * msDuration / 1000);
// 'volume' is UInt16 with range 0 thru Uint16.MaxValue ( = 65 535)
// we need 'amp' to have the range of 0 thru Int16.MaxValue ( = 32 767)
double amp = volume >> 2; // so we simply set amp = volume / 2
for (int step = 0; step < samples; step++)
{
short s = (short)(amp * Math.Sin(theta * (double)step));
writer.Write(s);
}
}
I'm targeting windows phone 8.1 silverlight platform

Answer 1

I got the solution for the problem: do the following before calling CopyTo()
mStrmStartDelimiter.Position = 0;
mStrmEndDelimiter.Position = 0;