Hi following is the two approaches for converting an existing byte array to the desired file in C# language.

Approach-1: Low-level coding

public void Convert()
{
byte[] fileBytes= new byte[stream.Length];

stream.Close();

using (Stream file = File.OpenWrite(@"c:\path\to\your\file\here.txt"))
{
file.Write(fileBytes, 0, fileBytes.Length);
}
}

Approach-2: Direct short cut

public void Convert(byte[] input)
{
File.WriteAllBytes(outputfileName, input);
}

There is not much to give an explanation for these approaches as those are well known.