Update src/Microsoft.OpenApi.Readers/V2/OpenApiDocumentDeserializer.cs

Author: baywet

src/Microsoft.OpenApi.Readers/V2/OpenApiDocumentDeserializer.cs

@@ -213,7 +213,11 @@ private static string BuildUrl(string scheme, string host, string basePath)
 
             int? port = null;
 
+#if NETSTANDARD2_1_OR_GREATER
             if (!String.IsNullOrEmpty(host) && host.Contains(':', StringComparison.OrdinalIgnoreCase))
+#else
+            if (!String.IsNullOrEmpty(host) && host.Contains(':'))
+#endif
             {
                 var pieces = host.Split(':');
                 host = pieces.First();