How to configure Azure App Service so that the cache-busting rewrite rules in our Web Forms app's web.config work?

Jan J. Vopalensky 0

In our ASP.NET 4.8 Web Forms app web.config file we have following rewrite rule under the

VenkateshDodda-MSFT 17,826 Reputation points Microsoft Employee

2023-02-02T12:06:59.7366667+00:00

@Jan J. Vopalensky Thanks you for reaching out to Microsoft Q&A, apologize for any inconvenience caused on this.

You can refer to this xdt transform sample and add the rewrite config for your web app using applicationhost.config file as mentioned here.

Jan J. Vopalensky 0

Thanks Venkatesh for your reply. I've added following XDT:

<?xml version="1.0"?>
<configuration xmlns:xdt="http://schemas.microsoft.com/XML-Document-Transform">
	<system.webServer xdt:Transform="InsertIfMissing">
		<rewrite xdt:Transform="InsertIfMissing">
			<rules xdt:Transform="InsertIfMissing">
				<rule name="fingerprint" xdt:Locator="Match(name)" xdt:Transform="RemoveAll" />
				<rule name="fingerprint">
					<match url="(.*)(v-[0-9]+/)(.*)$" />
					<action type="Rewrite" url="{R:1}{R:3}" />
				</rule>
			</rules>
		</rewrite>
	</system.webServer>
</configuration>

But I still see the same issue: the needed CSS/JS files cannot be found (404 error) - even after app restart.

Are there any other settings that I need to set?

Also, should I use use similar XDT method to copy/move our other settings from our app's web.config file in the <system.webServer> section? It seems to me those settings are ignored.

Jan J. Vopalensky 0 Reputation points

2023-02-03T03:03:08.0666667+00:00

Sorry: I meant to add a comment, not an answer.
VenkateshDodda-MSFT 17,826 Reputation points Microsoft Employee

2023-02-06T10:45:37.7466667+00:00

@Jan J. Vopalensky Thanks for your patience on this apologizes for the delay in my response.

I have checked with my team internally on this and they have confirmed that you can write those rewrite URL in web.config and it should work exact same in app service as in Azure VM.

Could you please help us more information like webapp name, F12 traces (after concealing any private details) showing the problem and also current behavior and expected result to check and assist you further on this.
VenkateshDodda-MSFT 17,826 Reputation points Microsoft Employee

2023-02-09T10:09:31.0566667+00:00

@Jan J. Vopalensky Just following up to see if you have a chance to check my previous response and help us with the requested information to check and assist you further.

1 answer

Jan J. Vopalensky 0 Reputation points

2023-02-09T15:54:49.91+00:00
I found the issue was caused by this rewrite rule we had at the wwwroot level :

<rule name="Ensure valid host header" stopProcessing="true"> <match url="(.*)" /> <conditions> <add input="{HTTP_HOST}" matchType="Pattern" negate="true" pattern="^((.*)\.xxxxxxx\.com|beta\.yyyyyyy\.com)$" ignoreCase="true" /> </conditions> </rule>

where: 'xxxx' and 'yyyy' are strings used by our app's domain name.

FYI - our app is running in a virtual app sub-folder, where the cache-busting rewrite rules are defined in its web.config file. Since our current Azure App Service testing does not use any of these strings in the domain name, the URL requests did not get through.
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VenkateshDodda-MSFT 17,826 Reputation points Microsoft Employee

2023-02-10T04:10:35.6+00:00

@Jan J. Vopalensky Thanks for sharing the solution and glad to hear that your problem has resolved.
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