using System.IO;
using System.Security.Cryptography;

...

public byte[] HashedFileWrite(string filename, Stream input)
{
    var hash_algorithm = MD5.Create();

    using(var file = File.OpenWrite(filename))
    {
        byte[] buffer = new byte[4096];
        int read = 0;

        while ((read = input.Read(buffer, 0, buffer.Length)) > 0)
        {
            hash_algorithm.TransformBlock(buffer, 0, read, null, 0);
            file.Write(buffer, 0, read);
        }

        hash_algorithm.TransformFinalBlock(buffer, 0, read);
    }

    return hash_algorithm.Hash;
}

private static byte[] CopyAndHash(string source, string target, Action<double> progress, Func<bool> isCanceled)
{
    using(var sha512 = SHA512.Create())
    using (var targetStream = File.OpenWrite(target))
    using (var cryptoStream = new CryptoStream(targetStream, sha512, CryptoStreamMode.Write))
    using (var sourceStream = File.OpenRead(source))
    {
        byte[] buffer = new byte[81920];
        int read;
        while ((read = sourceStream.Read(buffer, 0, buffer.Length)) > 0 && !isCanceled())
        {
            cryptoStream.Write(buffer, 0, read);

            progress?.Invoke((double) sourceStream.Length / sourceStream.Position * 100);
        }
    }

    File.SetAttributes(target, File.GetAttributes(source));

    return sha512.Hash;
   }
}

Stream s = File.Open("infile.dat");
Stream out = File.Create("outfile.dat");
HashWrapStream hasher = new HashWrapStream(out);
byte[] buffer=new byte[1024];
int read = 0;
while ((read=s.Read(buffer)!=0)
{
    hasher.Write(buffer);
}
long hash=hasher.GetComputedHash(); // get actual hash
hasher.Dispose();
s.Dispose();

//var ticks = **some_array_you_want_to_write_as_csv**

using (var memoryStream = new System.IO.MemoryStream())
            {
                using (var textWriter = new System.IO.StreamWriter(memoryStream))
                {
                    using (var csv = new CsvHelper.CsvWriter(textWriter))
                    {
                        csv.Configuration.DetectColumnCountChanges = true; //error checking
                        csv.Configuration.RegisterClassMap<TickDataClassMap>();
                        csv.WriteRecords(ticks);

                        textWriter.Flush();

                        //write to disk
                        using (var fileStream = new System.IO.FileStream(targetFileName, System.IO.FileMode.Create))
                        {
                            memoryStream.Position = 0;
                            memoryStream.CopyTo(fileStream);

                        }

                        //write sha256 hash, ensuring that the file was properly written
                        using (var sha256 = System.Security.Cryptography.SHA256.Create())
                        {
                            memoryStream.Position = 0;
                            var hash = sha256.ComputeHash(memoryStream);
                            using (var reader = System.IO.File.OpenRead(targetFileName))
                            {
                                System.IO.File.WriteAllText(targetFileName + ".sha256", hash.ConvertByteArrayToHexString());
                            }
                        }

                    }

                }
            }