RedirectToCanonicalUrlAttribute converts query strings to lower case

[claq2]

Query string parameters shouldn't be altered. Some systems, like OAuth2, expect values to be reflected as-is. (.NET code doesn't change them when you set RouteCollection.LowercaseUrls to true, only the path.)

Please make RedirectToCanonicalUrlAttribute not change query string parameters.

[RehanSaeed]

The query string is case sensitive for SEO. In my experience it's fairly rare to want to use a case sensitive query string but when you do, use [NoLowercaseQueryString].