Redirect .aspx url to one without it

You can do this in IIS with URL Rewrite module. You can configure it in IIS manager. Some examples are in the documentation. This redirecting rule should work.

<rewrite>
    <rules>
        <rule name="Redirect from aspx" stopProcessing="true">
            <match url="^(.+?).aspx" />
            <action type="Redirect" url="{R:1}" appendQueryString="true" />
        </rule>
    </rules>
</rewrite>