Reduce steps for string.Contains(string value) (#22008)

1 files changed, 8 insertions, 3 deletions

diff --git a/src/System.Private.CoreLib/shared/System/String.Searching.cs b/src/System.Private.CoreLib/shared/System/String.Searching.cs
index 893c2c7448..cce119b1d0 100644
--- a/src/System.Private.CoreLib/shared/System/String.Searching.cs
+++ b/src/System.Private.CoreLib/shared/System/String.Searching.cs
@@ -3,8 +3,6 @@
 // See the LICENSE file in the project root for more information.
 
 using System.Globalization;
-using System.Numerics;
-using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 using Internal.Runtime.CompilerServices;
 
@@ -14,7 +12,14 @@ namespace System
     {
         public bool Contains(string value)
         {
-            return (IndexOf(value, StringComparison.Ordinal) >= 0);
+            if (value == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.value);
+
+            return SpanHelpers.IndexOf(
+                ref _firstChar,
+                Length,
+                ref value._firstChar,
+                value.Length) >= 0;
         }
 
         public bool Contains(string value, StringComparison comparisonType)