How do you get a hexstring from a base10 string -or- from a number?

[Enjoys Math via Digitalmars-d-learn]

On Wednesday, 3 February 2016 at 23:43:45 UTC, Enjoys Math wrote:
> I am making a method called:
>
> @property string debugIDString() {
> in {
>   assert(super.toHash() == this.toHash());
> } body {
>
> }

body { // is currently:
   return to!string(this.toHash());
}

and is returning a base10 string, so how would I return a hex 
string so I can compare numbers displayed to the debugger 
addresses in visual D?