Use Convert.ToHexStringLower (#38965)

src/Cli/Microsoft.DotNet.Cli.Utils/Sha256Hasher.cs

@@ -20,7 +20,11 @@ public static string Hash(string text)
         {
             byte[] bytes = Encoding.UTF8.GetBytes(text);
             byte[] hash = SHA256.HashData(bytes);
+#if NET9_0_OR_GREATER
+            return Convert.ToHexStringLower(hash);
+#else
             return Convert.ToHexString(hash).ToLowerInvariant();
+#endif
         }
 
         public static string HashWithNormalizedCasing(string text)

src/Containers/Microsoft.NET.Build.Containers/DigestUtils.cs

@@ -25,6 +25,6 @@ internal static string GetSha(string str)
         Span<byte> hash = stackalloc byte[SHA256.HashSizeInBytes];
         SHA256.HashData(Encoding.UTF8.GetBytes(str), hash);
 
-        return Convert.ToHexString(hash).ToLowerInvariant();
+        return Convert.ToHexStringLower(hash);
     }
 }

src/Containers/Microsoft.NET.Build.Containers/Layer.cs

@@ -184,8 +184,8 @@ static UnixFileMode DetermineFileMode(FileSystemInfo file)
             }
         }
 
-        string contentHash = Convert.ToHexString(hash).ToLowerInvariant();
-        string uncompressedContentHash = Convert.ToHexString(uncompressedHash).ToLowerInvariant();
+        string contentHash = Convert.ToHexStringLower(hash);
+        string uncompressedContentHash = Convert.ToHexStringLower(uncompressedHash);
 
         string layerMediaType = manifestMediaType switch
         {

src/Tasks/Microsoft.NET.Build.Tasks/AllowEmptyTelemetry.cs

@@ -76,7 +76,7 @@ private static string HashWithNormalizedCasing(string text)
 #endif
 #if NET
             byte[] hash = System.Security.Cryptography.SHA256.HashData(utf8UpperBytes);
-            return Convert.ToHexString(hash).ToLowerInvariant();
+            return Convert.ToHexStringLower(hash);
 #endif
         }
     }

test/Microsoft.NET.Build.Containers.IntegrationTests/LayerEndToEndTests.cs

@@ -91,8 +91,8 @@ private static void VerifyDescriptorInfo(Layer l)
             }
         }
 
-        Assert.Equal(Convert.ToHexString(hashBytes), l.Descriptor.Digest.Substring("sha256:".Length), ignoreCase: true);
-        Assert.Equal(Convert.ToHexString(uncompressedHashBytes), l.Descriptor.UncompressedDigest?.Substring("sha256:".Length), ignoreCase: true);
+        Assert.Equal(Convert.ToHexStringLower(hashBytes), l.Descriptor.Digest.Substring("sha256:".Length));
+        Assert.Equal(Convert.ToHexStringLower(uncompressedHashBytes), l.Descriptor.UncompressedDigest?.Substring("sha256:".Length));
     }
 
     TransientTestFolder? testSpecificArtifactRoot;