using System.Text.RegularExpressions; var slnFile = Directory.GetFiles(@"./", "*.sln").First(); var content = File.ReadAllText(slnFile); content = Regex.Replace( content, "Project\\(\"{2150E333-8FDC-42A3-9474-1A3956D46DE8}\"\\) = \"meta\", \"meta\", \"{5198A03D-0CAC-4828-A807-34A693F73859}\"(?:.|\n)*?EndProject", $$""" Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "meta", "meta", "{5198A03D-0CAC-4828-A807-34A693F73859}" {{'\t'}}ProjectSection(SolutionItems) = preProject {{string.Join('\n', Directory.GetFiles(@"./", "*").Where(x => !x.EndsWith(".sln") && !x.EndsWith(".user")) .Select(x=>$"\t\t{Path.GetFileName(x)} = {Path.GetFileName(x)}") )}} {{'\t'}}EndProject """ ); Console.WriteLine(content); File.WriteAllText(slnFile, content);