Habe gerade eben das vb in den Themen gesehen. Obwohl VB nicht meine favorisierte Sprache ist.

Imports System.IO

Module Module1
    Sub Main()
        Dim oldFileName As String
        Dim newFileName As String
        Dim hasRead As Integer
        Dim fileBuffer(8192) As Byte
        Dim fsIn As FileStream
        Dim fsOut As FileStream

        oldFileName = "G:\TEST.TXT"
        newFileName = "G:\TEST_NEU.TXT"
        hasRead = 0
        fsIn = New FileStream(oldFileName, FileMode.Open, FileAccess.Read)
        fsOut = New FileStream(newFileName, FileMode.CreateNew, FileAccess.Write)
        Do
            hasRead = fsIn.Read(fileBuffer, 0, fileBuffer.Length)
            ' hier was mit dem Puffer anstellen
            fsOut.Write(fileBuffer, 0, hasRead)
        Loop While hasRead = fileBuffer.Length
    End Sub

End Module

// C#

string oldFileName = @"G:\TEST.TXT";
string newFileName = @"G:\TEST_NEU.TXT";

int hasRead = 0;
byte[] buffer = new byte[8192];

FileStream fsIn = new FileStream(oldFileName, FileMode.Open, FileAccess.Read);
FileStream fsOut = new FileStream(newFileName, FileMode.CreateNew, FileAccess.Write);

do
{
   hasRead = fsIn.Read(buffer, 0, buffer.Length);
                
   // Hier irgendwas mit dem Puffer anstellen
                
   fsOut.Write(buffer, 0, hasRead);
} while (hasRead == buffer.Length);