C# file splitting and file merging

        void SplitFile()
        {

            string sourceFile = "Old.mp4"; //Source file path            string outputFile1 = ""; //First output file path (10KB)            string outputFile2 = ""; //Second output file path (remainder)
            int firstFileSize = 10 * 1024; // The first file size is 10KB (10 * 1024 bytes)
            //Open source file            using (FileStream sourceStream = (sourceFile))
            {
                //Create the first output file                using (FileStream outputStream1 = (outputFile1))
                {
                    // Read and write 10KB of data from the first file                    byte[] buffer = new byte[firstFileSize];
                    int bytesRead = (buffer, 0, );
                    (buffer, 0, bytesRead);
                }

                //Create a second output file                using (FileStream outputStream2 = (outputFile2))
                {
                    //Read and write remaining data                    byte[] buffer = new byte[1024]; // 1KB buffer                    int bytesRead;
                    while ((bytesRead = (buffer, 0, )) > 0)
                    {
                        (buffer, 0, bytesRead);
                    }
                }
            }


        }

        void MergeFile()
        {

            string file1 = ""; //The first binary file path            string file2 = ""; //Second binary file path            string outputFile = "Merged.mp4"; // Merged file path
            //Open the output file stream            using (FileStream outputStream = (outputFile))
            {
                // Read and write the first file                using (FileStream inputStream = (file1))
                {
                    (outputStream); // Copy the contents of the first file to the output file                }

                // Read and write the second file                using (FileStream inputStream = (file2))
                {
                    (outputStream); // Copy the contents of the second file to the output file                }
            }

        }