With a web.config transform, how do you inject a canonical url rule at the top?

Question

Within an ASP.Net project, for the release build's Web.Config (using a Web.Release.Config transform file), how do you inject a canonical url rule in the rewrite section?

Answer 1

Below is an example that worked for me, you have to use an XPath selector in order to inject your rule into the proper position via the xdt:Transform property.

<?xml version="1.0" encoding="utf-8"?>
<configuration xmlns:xdt="http://schemas.microsoft.com/XML-Document-Transform">
    <system.webServer>
        <rewrite>
            <rules>
                <rule name="CanonicalHostNameRule1" enabled="true" stopProcessing="true" 
                    xdt:Transform="InsertBefore(/configuration/system.webServer/rewrite/rules/rule[position() = 1])"
                >
                    <match url="(.*)" />
                    <conditions>
                        <add input="{HTTP_HOST}" negate="true" pattern="^www\.yoursite\.com$" />
                    </conditions>
                    <action type="Redirect" url="http://www.yoursite.com/{R:1}" />
                </rule>
            </rules>
        </rewrite>
    </system.webServer>
</configuration>

You can do some other interesting replacements using xpath statements as well. I hope the above example is helpful as StackOverflow is generally where I look first for this type of thing these days.