IIS: Rewrite URL with regex but keep query strings - regex

Question

I'm have the following link
https://example.com/myapp/green?&lang=en&instance=some%20instance
I need to rewrite it to the following link
https://example.com/myapp?color=green&lang=en&instance=some%20instance
The color in the link can be any color but it needs to be rewritten like in the 2nd link so that the trailing slash is replaced with a ? followed by the word color= and the ? at the end of the color word needs to be removed.
/myapp/green? becomes /myapp?color=green,
/myapp/blue? becomes /myapp?color=blue
and so forth, all while keeping the rest of the query string &lang=en&instance=some%20instance intact
I've tried regexing my way out of this but I usually catch everything or unintentionally omit the rest of the query string.
Any ideas on what's the best approach?
EDIT: noticed that IIS, when applying to application level (not website level), the input URL path is after '/myapp/' and I need that trailing slash removed. Does this mean I'll have to apply it to the website level?

Answer 1

You could use below url rewrite rule(add this rule at site level):
<rule name="color query" enabled="true" stopProcessing="true">
<match url="myapp/(.*)/$" />
<conditions logicalGrouping="MatchAll" trackAllCaptures="false">
<add input="{QUERY_STRING}" pattern="lang=(.*)&instance=(.*)" />
</conditions>
<action type="Redirect" url="http://www.sample1.com/myapp?color={R:1}&lang={C:1}&instance={C:2}" appendQueryString="false" />
</rule>
Note: you could not remove the myapp/ from URL it will be added automatically in URL.