merge_cs.py

# This program does the following
# 1. Collect all the using statements of all the files
# 2. Collect the bodies of all the files (everything after the using statement)
# 3. Create the final merged file, which is all the using statements, followed by all the bodies.

import os
import sys

if len(sys.argv) != 2:
    print('This program takes exactly one arguments: the folder containing cs files to merge')
    exit(-1)

merge_folder = sys.argv[1]

using_statements = []   # contains the using statements of each file
file_bodies = []        # contains everything after the using statements of each file

for subdir, dirs, files in os.walk(merge_folder):
    for filename in files:
        filepath = os.path.join(subdir, filename)
        _, ext = os.path.splitext(filename)

        if ext != '.cs':
            continue

        with open(filepath, encoding='utf-8') as fileToMerge:
            entire_file = fileToMerge.read()

        # find something like 'namespace Mono.Xml.Xsl.Operations' and then split the file just before 'namespace'
        splitLocation = entire_file.find('namespace')

        if splitLocation == -1:
            print("ERROR: Couldn't find namespace keyword in file '{}'".format(filepath))
            exit(-1)

        using_statements.append(entire_file[:splitLocation])
        file_bodies.append(entire_file[splitLocation:])

# output to STDOUT
print(''.join(using_statements))
print(''.join(file_bodies))