Skip to main content

Custom web.config transforms

One of the nice features of Visual Studio 2012(and also Visual Studio 2010) is the ability to use Web.config transformations.
However the list of supported transforms is  somewhat limited. I was looking for a way to execute a transformation only if a specific element doesn’t exist yet in your root web.config file. I discovered that Web.config transform engine can be extended to support additional transformations.
On the AppHarbor blog, I found a sample transformation that exactly did what I needed: 
using System.Linq;
using System.Xml;
using Microsoft.Web.Publishing.Tasks;

namespace AppHarbor.TransformTester.Transforms
{
    public class Merge : Transform
    {
        public Merge() : base(TransformFlags.UseParentAsTargetNode)
        {}

        protected override void Apply()
        {
            Apply((XmlElement)TargetNode, (XmlElement)TransformNode);
        }

        public void Apply(XmlElement targetElement, XmlElement transformElement)
        {
            var targetChildElement = targetElement.ChildNodes.OfType<XmlElement>()
                .FirstOrDefault(x => x.LocalName == transformElement.LocalName);
            if (targetChildElement == null)
            {
                targetElement.AppendChild(transformElement);
                return;
            }

            foreach (var transformChildElement in transformElement.ChildNodes
                .OfType<XmlElement>())
            {
                Apply(targetChildElement, transformChildElement);
            }
        }
    }
}
If you want to use this transform you need to add it using the xdt:Import element. You can place that element inside the xml document anywhere immediately under the root element. This element will allow us to utilize our own transform class. It only has 3 possible attributes.

  • namespace – This is the namespace which the transform is contained in  
  • path – This is the full path to the assembly  
  • assembly – This is the assembly name which contains the transform
You can only use one of the two; path and assembly.

So the import will look like this  in your transformation XML:

   

<xdt:Import assembly="AppHarbor.TransformTester" namespace="AppHarbor.TransformTester.Transforms"/>

From that moment one you can start applying it:


<configuration xmlns:xdt="http://schemas.microsoft.com/XML-Document-Transform">    
<connectionStrings xdt:Transform="Merge" />    
 <connectionStrings>        
  <add name="bar" connectionString="value" xdt:Transform="Insert"/>    
 </connectionStrings>
</configuration>


The only disadvantage I think is that you have to install this transform assembly on all developer pc’s if they want to execute these transformations locally.

Popular posts from this blog

DevToys–A swiss army knife for developers

As a developer there are a lot of small tasks you need to do as part of your coding, debugging and testing activities.  DevToys is an offline windows app that tries to help you with these tasks. Instead of using different websites you get a fully offline experience offering help for a large list of tasks. Many tools are available. Here is the current list: Converters JSON <> YAML Timestamp Number Base Cron Parser Encoders / Decoders HTML URL Base64 Text & Image GZip JWT Decoder Formatters JSON SQL XML Generators Hash (MD5, SHA1, SHA256, SHA512) UUID 1 and 4 Lorem Ipsum Checksum Text Escape / Unescape Inspector & Case Converter Regex Tester Text Comparer XML Validator Markdown Preview Graphic Color B

Help! I accidently enabled HSTS–on localhost

I ran into an issue after accidently enabling HSTS for a website on localhost. This was not an issue for the original website that was running in IIS and had a certificate configured. But when I tried to run an Angular app a little bit later on http://localhost:4200 the browser redirected me immediately to https://localhost . Whoops! That was not what I wanted in this case. To fix it, you need to go the network settings of your browser, there are available at: chrome://net-internals/#hsts edge://net-internals/#hsts brave://net-internals/#hsts Enter ‘localhost’ in the domain textbox under the Delete domain security policies section and hit Delete . That should do the trick…

Azure DevOps/ GitHub emoji

I’m really bad at remembering emoji’s. So here is cheat sheet with all emoji’s that can be used in tools that support the github emoji markdown markup: All credits go to rcaviers who created this list.