Merge two or more mp3 files in C# using naudio library

mashup.cs

    /// <summary>
    /// Creates a mashup of two or more mp3 files by using naudio
    /// </summary>
    /// <param name="files">Name of files as an string array</param>
    /// These files should be existing in a temporay folder
    /// <returns>The path of mashed up mp3 file</returns>
    public static string CreateMashup (string[] files) {
        // because there is no mash up with less than 2 files
        if (files.Count () < 2) {
            throw new Exception ("Not enough files selected!");
        }

        try {
            // Create a mixer object
            // This will be used for merging files together
            var mixer = new WaveMixerStream32 {
                AutoStop = true
            };

            // Set the path to store the mashed up output file
            var outputFile = Path.Combine (Path.GetTempPath (),
                ConfigurationManager.AppSettings["OutputDirName"],
                Guid.NewGuid ().ToString () + ".mp3");

            foreach (var file in files) {
                // for each file -
                // check if it exists in the temp folder
                var filePath = Path.Combine (Path.GetTempPath (),
                    ConfigurationManager.AppSettings["InputDirName"], file + ".mp3");
                if (File.Exists (filePath)) {
                    // create mp3 reader object
                    var reader = new Mp3FileReader (filePath);

                    // create a wave stream and a channel object
                    var waveStream = WaveFormatConversionStream.CreatePcmStream (reader);
                    var channel = new WaveChannel32 (waveStream) {
                        //Set the volume
                        Volume = 0.5f
                    };

                    // add channel as an input stream to the mixer
                    mixer.AddInputStream (channel);
                }
            }

            // convert wave stream from mixer to mp3
            var wave32 = new Wave32To16Stream (mixer);
            var mp3Writer = new LameMP3FileWriter (outputFile, wave32.WaveFormat, 128);
            wave32.CopyTo (mp3Writer);

            // close all streams
            wave32.Close ();
            mp3Writer.Close ();

            // return the mashed up file path
            return outputFile;
        } catch (Exception) {
            // TODO: handle exception
            throw;
        }
    }

@ShiliSaghi When I created this app, the version I used for .Net was 4.6.1. See here - https://github.com/gautamdhameja/mtf-mashup/blob/master/src/mashup/mtf-mashup.api/mtf-mashup.api.csproj#L18
The NAudio version I was using was 1.8.3 - https://github.com/gautamdhameja/mtf-mashup/blob/master/src/mashup/mtf-mashup.api/mtf-mashup.api.csproj#L95

Also, here if the full code available for reference - https://github.com/gautamdhameja/mtf-mashup/tree/master/src/mashup
Hope this helps.