IIS rewrite rule one query parameter with multiple values - regex

Question

IIS web.config:
I am trying to redirect a path like
mysite.com/?myparam=123,321,112
to
mysite.com/mypage?param=123,321,112
<rule name="Multiple QueryValue String Rewrite" enabled="true">
<match url="(.*)" />
<conditions>
<add input="{QUERY_STRING}" pattern="myparam=(.\,)" />
</conditions>
<action type="Redirect" url="/mypage?param={C:0}" appendQueryString="false" />
</rule>
But whatever i try, it will only forwards the first param. leading to
/mypage?param=123
I have tried multiple combination of {C} and pattern regex.

Answer 1

IMPORTANT: before try something new remember ALWAYS to clear the cache of browser! it's mandatory.
Now...
the pattern you use is not correct, you have to use one suggested by Wiktor Stribiżew
So using pattern="myparam=([0-9\,]*) with url="/mypage?param={C:1}" try this:
<rule name="Multiple QueryValue String Rewrite" enabled="true">
<match url="(.*)" />
<conditions>
<add input="{QUERY_STRING}" pattern="myparam=([0-9\,]*)" />
</conditions>
<action type="Redirect" url="/mypage?param={C:1}" appendQueryString="false" />
</rule>
If that is not correct there is something wrong in "," character... something about encoding?
if you try this one what happened?:
<rule name="Multiple QueryValue String Rewrite" enabled="true">
<match url="(.*)" />
<conditions>
<add input="{QUERY_STRING}" pattern="myparam=([0-9]*)\,([0-9]*)\,([0-9]*)" />
</conditions>
<action type="Redirect" url="/mypage?param={C:1},{C:2},{C:3}" appendQueryString="false" />
</rule>

Answer 2

If only for mysite.com/?myparam=123,321,112, you can try the following URL rewriting rules:
<rule name="Multiple QueryValue String Rewrite" enabled="true">
<match url="(.*)" />
<conditions>
<add input="{QUERY_STRING}" pattern="myparam=(.*)" />
</conditions>
<action type="Redirect" url="/mypage?param={C:1}" appendQueryString="false" />
</rule>