Replace GUID in web.config during publish

Question

I'm looking for a way to have a GUID in my web.config file, which gets transformed into a new GUID at publish-time.

For example:

<add key="someGuid" value="aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" />

and when you publish the app using MSBuild or Visual Studio's publish screen, the resulting config file, after transformation, contains a brand-new GUID, like:

<add key="someGuid" value="ab15c61ba16d1651a6c89a621d64c4f8" />

Basically, I need a new GUID every time I publish the app, but also need the ability to replace this GUID on demand without a full recompile.

Before I build something custom, using a placeholder and replacing the text manually, I wanted to see if there's a config transform or built-in MSBuild function that could help.

Answer 1

In MSBuild, you can create a new GUID like this

<PropertyGroup>
  <SomeGuid>$([System.Guid]::NewGuid())</SomeGuid>
</PropertyGroup>

And then you can use the XmlPoke task to make the replacement using your newly created property $(SomeGuid).

Excerpted from in the book MSBuild Trickery tricks #9 and #101