From 6a977e9be9af1c31f6bf017c7829fc5f02550525 Mon Sep 17 00:00:00 2001
From: Anirudh Agnihotry <anirudhagnihotry098@gmail.com>
Date: Tue, 27 Feb 2018 15:56:23 -0800
Subject: [PATCH] Bug in GetFullPath(basePath, Path) (#16598)

* GetFullPath and GetRootLength Corrected

* Removed getpathroot

* using span

* "\\" changed to @"\"
---
 src/mscorlib/shared/System/IO/Path.Windows.cs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/mscorlib/shared/System/IO/Path.Windows.cs b/src/mscorlib/shared/System/IO/Path.Windows.cs
index 6a8745d12e26..c92211f73150 100644
--- a/src/mscorlib/shared/System/IO/Path.Windows.cs
+++ b/src/mscorlib/shared/System/IO/Path.Windows.cs
@@ -98,8 +98,8 @@ public static string GetFullPath(string path, string basePath)
                 {
                     // No matching root, root to specified drive
                     // "D:Foo" and "C:\Bar" => "D:Foo"
-                    // "D:\Foo" and "\\?\C:\Bar" => "\\?\D:\Foo"
-                    combinedPath = path.Insert(2, "\\");
+                    // "D:Foo" and "\\?\C:\Bar" => "\\?\D:\Foo"
+                    combinedPath = PathInternal.IsDevice(basePath) ? CombineNoChecksInternal(basePath.AsSpan().Slice(0, 4), path.AsSpan().Slice(0, 2), @"\", path.AsSpan().Slice(2)) : path.Insert(2, "\\");
                 }
             }
             else