Change exception throwing in Path.GetRelativePath (#25047)

* Fix Path.GetRelativePath throws ArgumentNullException when relativeTo is empty string

* Fix ArgumentException for relativeTo

diff --git a/src/System.Private.CoreLib/shared/System/IO/Path.cs b/src/System.Private.CoreLib/shared/System/IO/Path.cs
index 7412eb6..c581ee6 100644 (file)
--- a/src/System.Private.CoreLib/shared/System/IO/Path.cs
+++ b/src/System.Private.CoreLib/shared/System/IO/Path.cs
@@ -812,8 +812,18 @@ namespace System.IO
 
         private static string GetRelativePath(string relativeTo, string path, StringComparison comparisonType)
         {
-            if (string.IsNullOrEmpty(relativeTo)) throw new ArgumentNullException(nameof(relativeTo));
-            if (PathInternal.IsEffectivelyEmpty(path.AsSpan())) throw new ArgumentNullException(nameof(path));
+            if (relativeTo == null)
+                throw new ArgumentNullException(nameof(relativeTo));
+
+            if (PathInternal.IsEffectivelyEmpty(relativeTo.AsSpan()))
+                throw new ArgumentException(SR.Arg_PathEmpty, nameof(relativeTo));
+
+            if (path == null)
+                throw new ArgumentNullException(nameof(path));
+
+            if (PathInternal.IsEffectivelyEmpty(path.AsSpan()))
+                throw new ArgumentException(SR.Arg_PathEmpty, nameof(path));
+
             Debug.Assert(comparisonType == StringComparison.Ordinal || comparisonType == StringComparison.OrdinalIgnoreCase);
 
             relativeTo = GetFullPath(relativeTo);