Edit all C# files inside a project

vs.ps1

# this requires NuGet to be installed, so it will bring the PowerShell command line
# and the EnvDTE object. See: https://msdn.microsoft.com/en-us/library/EnvDTE.aspx

function DoItOnProjectItem($item) {
	$doc = $item;
	if ($doc.Name -match "\.cs$") {
		write-host $doc.Name;

		# open and display document
		$foo = $doc.Open("{7651A701-06E5-11D1-8EBD-00A0C90F26EA}"); # vsViewKindCode -> to display code window
		# it's possible to not activate the document (that won't display it),
		# but commands like remove/sort using and format won't work
		$doc.Document.Activate();
		$sel = $doc.Document.Selection;

		$sel.StartOfDocument();

		# add some using
		$sel.Insert("using X.Y.Z;");$sel.NewLine(1);
		# ...

		# and remove other ones
		if ($sel.FindText("using Z.Y.X", 0)) { $sel.SelectLine(); $sel.Delete(); }
		
		# make some text replacement
		while ($sel.FindText("Sender.Send", 0)) { $sel.Insert("SysLogSender.Send"); }

		# remove and sort usings
		$dte.ExecuteCommand("EditorContextMenus.CodeWindow.OrganizeUsings.RemoveAndSort");
		# and cleanly format document ;)
		$dte.ExecuteCommand("Edit.FormatDocument");

		$doc.Save();
		$doc.Document.Close();
	}

}
function ModifyProject($projName) {
	$dte.Solution.Projects | foreach-object {
		$proj = $_;
		if ($proj.Name -eq $projName) {
			Write-Host "Project '$projName' found."
			$proj.ProjectItems | foreach-object {
				DoItOnProjectItem($_);
				# do the same on sub-items (useful for code-behind)
				$_.ProjectItems | foreach-object { DoItOnProjectItem($_); }
			}
		}
	}
}

ModifyProject("Project Name");