Symlink test one off

Program.cs

using System;
using BetterWin32Errors;
using System.IO;
using System.Threading;
using System.Threading.Tasks;
using System.Runtime.InteropServices;
using System.Text;

namespace Tgstation.Server.Host
{
	/// <summary>
	/// Native methods used by the code
	/// </summary>
	static class NativeMethods
	{
		/// <summary>
		/// See https://docs.microsoft.com/en-us/windows/desktop/api/winbase/nf-winbase-createsymboliclinka#parameters
		/// </summary>
		[Flags]
		public enum CreateSymbolicLinkFlags : int
		{
			None = 0,
			Directory = 1,
			AllowUnprivilegedCreate = 2
		}

		/// <summary>
		/// See https://docs.microsoft.com/en-us/windows/desktop/api/winuser/nf-winuser-getwindowthreadprocessid
		/// </summary>
		[DllImport("user32.dll")]
		public static extern int GetWindowThreadProcessId(IntPtr hWnd, out int lpdwProcessId);

		/// <summary>
		/// See https://docs.microsoft.com/en-us/windows/desktop/api/winuser/nf-winuser-findwindoww
		/// </summary>
		[DllImport("user32.dll", CharSet = CharSet.Unicode)]
		public static extern IntPtr FindWindow(string lpClassName, string lpWindowName);

		/// <summary>
		/// See https://docs.microsoft.com/en-us/windows/desktop/api/winuser/nf-winuser-sendmessage
		/// </summary>
		[DllImport("user32.dll")]
		public static extern int SendMessage(IntPtr hWnd, int wMsg, IntPtr wParam, IntPtr lParam);

		/// <summary>
		/// See https://msdn.microsoft.com/en-us/library/ms633493(v=VS.85).aspx
		/// </summary>
		public delegate bool EnumWindowProc(IntPtr hwnd, IntPtr lParam);

		/// <summary>
		/// See https://docs.microsoft.com/en-us/windows/desktop/api/winuser/nf-winuser-enumchildwindows
		/// </summary>
		[DllImport("user32.dll")]
		public static extern bool EnumChildWindows(IntPtr window, EnumWindowProc callback, IntPtr lParam);

		/// <summary>
		/// See https://docs.microsoft.com/en-us/windows/desktop/api/winuser/nf-winuser-getwindowtextw
		/// </summary>
		[DllImport("user32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
		public static extern int GetWindowText(IntPtr hWnd, StringBuilder lpString, int nMaxCount);

		/// <summary>
		/// See https://msdn.microsoft.com/en-us/library/windows/desktop/aa378184(v=vs.85).aspx
		/// </summary>
		[DllImport("advapi32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
		public static extern bool LogonUser(string lpszUsername, string lpszDomain, string lpszPassword, int dwLogonType, int dwLogonProvider, out IntPtr phToken);

		/// <summary>
		/// See https://docs.microsoft.com/en-us/windows/desktop/api/winbase/nf-winbase-createsymboliclinkw
		/// </summary>
		[DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
		public static extern bool CreateSymbolicLink(string lpSymlinkFileName, string lpTargetFileName, CreateSymbolicLinkFlags dwFlags);
	}
}


namespace Tgstation.Server.Host.IO
{
	/// <summary>
	/// <see cref="ISymlinkFactory"/> for windows systems
	/// </summary>
	sealed class WindowsSymlinkFactory
	{
		/// <inheritdoc />
		public Task CreateSymbolicLink(string targetPath, string linkPath, CancellationToken cancellationToken) => Task.Factory.StartNew(() =>
		{
			if (targetPath == null)
				throw new ArgumentNullException(nameof(targetPath));
			if (linkPath == null)
				throw new ArgumentNullException(nameof(linkPath));

			//check if its not a file
			var flags = File.Exists(targetPath) ? NativeMethods.CreateSymbolicLinkFlags.None : NativeMethods.CreateSymbolicLinkFlags.Directory;

			flags |= NativeMethods.CreateSymbolicLinkFlags.AllowUnprivilegedCreate;

			cancellationToken.ThrowIfCancellationRequested();
			if (!NativeMethods.CreateSymbolicLink(linkPath, targetPath, flags))
			{
				if (Win32Exception.GetLastWin32Error() == Win32Error.ERROR_INVALID_PARAMETER) //SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE isn't supported
				{
					flags &= ~NativeMethods.CreateSymbolicLinkFlags.AllowUnprivilegedCreate;
					if (NativeMethods.CreateSymbolicLink(linkPath, targetPath, flags))
						return;
				}
				throw new Win32Exception();
			}
		}, cancellationToken, TaskCreationOptions.LongRunning, TaskScheduler.Current);
	}
}

namespace ConsoleApp2
{
	class Program
	{
		static async Task Main(string[] args)
		{
			try
			{
				Console.WriteLine("Symlinking \"C:\\TGS4_INSTANCES\\STARTREK13\\Configuration\\GameStaticFiles\\config\" to \"C:\\TGS4_INSTANCES\\STARTREK13\\Game\\53278a00-92e5-48ee-9083-7635367f0a28\\A\\config\"");
				await new Tgstation.Server.Host.IO.WindowsSymlinkFactory().CreateSymbolicLink("C:\\TGS4_INSTANCES\\STARTREK13\\Configuration\\GameStaticFiles\\config", "C:\\TGS4_INSTANCES\\STARTREK13\\Game\\53278a00-92e5-48ee-9083-7635367f0a28\\A\\config", default).ConfigureAwait(false);
				Console.WriteLine("Done!");
			}
			catch (Exception e)
			{
				Console.WriteLine(e.ToString());
			}
			Console.WriteLine("Press any key to continue...");
			Console.ReadKey();
		}
	}
}