Bug in GetFullPath(basePath, Path) (#16598)

* GetFullPath and GetRootLength Corrected

* Removed getpathroot

* using span

* "\\" changed to @"\"

diff --git a/src/mscorlib/shared/System/IO/Path.Windows.cs b/src/mscorlib/shared/System/IO/Path.Windows.cs
index 6a8745d12e26f05b30e30a53a7362aa15bc41d59..c92211f731502e313b59d9dbb19595a0ce084b63 100644 (file)
--- a/src/mscorlib/shared/System/IO/Path.Windows.cs
+++ b/src/mscorlib/shared/System/IO/Path.Windows.cs
@@ -98,8 +98,8 @@ namespace System.IO
                 {
                     // 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