Compressing file in C#

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C#

binary

compress

compression

hi I wanted to ask few question about files
For example mp3 file
When read as a binary array of bytes
For this I use algorithms to reduce the size of the byte array to a string or char would later become serious difficulties for his return or not?
Because if I use the Hoffman algorithm(for example),the byte array should become to what type of value to make that happen
this is my code for read and write the file

FileStream iFile = new FileStream(@"E:\Work\Project\Compressing\Data\Old Data\01.mp3", FileMode.Open);
                            long lengthInBytes = iFile.Length;
                            BinaryReader bin = new BinaryReader(iFile);
                            byte[] byteArray = bin.ReadBytes((int)lengthInBytes);
                            System.Text.Encoding encEncoder = System.Text.ASCIIEncoding.ASCII;
                            string str = encEncoder.GetString(byteArray);
                            byte[] byteOut = Encoding.ASCII.GetBytes(str);
                            var bw = new BinaryWriter(File.Open(@"E:\Work\Project\Compressing\Data\New Data\01.mp3", FileMode.OpenOrCreate));
                            bw.Write(byteArray);

Thank you for taking the time

What I have tried:

i used that code for read and write the file