After doing an investigation on some performance traces collected from some mvc aspnet applications scenarios we found that a considerable amount of char[] objects were allocated on the GC Heap which are coming from Uri.UnescapeDataString codepath that is calling UriHelper.UnescapeString (source code) which receives a char[] as the destination of the unescaped string and then creating a string from that char[].

I know it would be a big change but we could probably consider using the sourceString that is already allocated or using a PooledStringBuilder which uses an ArrayPool for the buffer cache as explained here:

• Port System.Net.WebUtility missing members corefx#13875 (comment)

/cc @danmosemsft @jkotas @stephentoub