Concatenate wav fales C# (generated + recorded)

Good night dear!

Please, as I do to join audios being recorded 1.wav and 2.wav generated by a text for spech API (microsoft azure). I tried a code snippet below it works for two recorded audios, but for this example it does not perform the audio creation 3.wav (WaveFileWriter.CreateWaveFile16 ("3.wav", mixer);).

I believe the problem is a difference in the "bit rate" of the files, could that be? How can I fix it?

using NAudio.Wave;
using NAudio.Wave.SampleProviders;

using (var reader1 = new AudioFileReader("1"))
using (var reader2 = new AudioFileReader("2.wav"))
{
   var mixer = new MixingSampleProvider(new[] { reader1, reader2 });
   WaveFileWriter.CreateWaveFile16("3.wav", mixer);
}