I am using Cake everywhere I can for my builds. It is such a nice way to define your builds in a C# DSL and run them on any environment.

Recently I had the need to patch a bunch of attributes in some XML files. Of course Cake has a tool for that! This is called XmlPoke. This tool along with a little bit of XPath knowledge and you are ready to update your XML files!

Lets say you want to update your AndroidManifest.xml with the newest versions for your App. This is usually done in the root element of the manifest, funnily enough called manifest:

<manifest 
    xmlns:android="http://schemas.android.com/apk/res/android"
    package="dk.ostebaronen.cheesyapp"
    android:versionCode="1"
    android:versionName="1.2.3"

The two attributes android:versionCode and android:versionName are the ones you want to update.

So first thing needed to be done is to load the namespaces. Even if you have a namespace looking like xmlns="http://some.schema.com/" it needs to be loaded and used in the XPath. To load these XmlPoke has a XmlPokeSettings class:

var settings = new XmlPokeSettings
{
    Namespaces = new Dictionary<string, string> 
    {
        {"android", "http://schemas.android.com/apk/res/android"}
    }
};

In the case of the Android Manifest, we only have the android namespace. In the Namespaces dictionary, you would otherwise load all the namespaces that you need for your XPath queries. In the case of a naked xmlns you would also name it something, it could be called root.

With the settings in place we are ready to modify the Android Manifest with the XmlPoke alias. The XPath for the two attributes would be, /manifest/@android:versionCode and /manifest/@android:versionName. Usage in Cake would be as follows:

XmlPoke(manifestFilePath, "/manifest/@android:versionCode",
    versionCode, settings);

XmlPoke(manifestFilePath, "/manifest/@android:versionName",
    versionName, settings);

Tying all this information together in a Cake Task:

Task("Update-Android-Manifest-Version")
    .Does(() => 
{
    var versionCode = "2";
    var versionName = "1.2.4";

    var settings = new XmlPokeSettings
    {
        Namespaces = new Dictionary<string, string> 
        {
            {"android", "http://schemas.android.com/apk/res/android"}
        }
    };

    XmlPoke(manifestFilePath, "/manifest/@android:versionCode", 
        versionCode, settings);
    XmlPoke(manifestFilePath, "/manifest/@android:versionName", 
        versionName, settings);
});

For versionCode and versionName I like to use GitVersion to calculate these, but you could load these from somewhere else, or they could be arguments to your Cake script, it doesn’t really matter as long as they are strings.

Lets take a look at how this looks when you have a naked xmlns declaration. Here is what the root looks like for a Azure Service Fabric ApplicationManifest.xml file:

<ApplicationManifest 
    xmlns:xsd="http://www.w3.org/2001/XMLSchema"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    ApplicationTypeName="CheesyApp"
    ApplicationTypeVersion="1.2.3"
    xmlns="http://schemas.microsoft.com/2011/01/fabric">

In this case we still need some namespace declarations:

var settings = new XmlPokeSettings
{
    Namespaces = new Dictionary<string, string> 
    {
        {"sf", "http://schemas.microsoft.com/2011/01/fabric"}
    }
};

xsi and xsd are not super important, unless you are going to query nodes using these later on. But to update the ApplicationTypeVersion we need the naked namespace.

The query in this case would look like /sf:ApplicationManifest/@ApplicationTypeVersion. These Service Fabric Application Manifests also have some ServiceManifestRef nodes with ServiceManifestVersion for each of the services you have in your app.

<ApplicationManifest ApplicationTypeVersion="1.2.3"
    xmlns="http://schemas.microsoft.com/2011/01/fabric">
    <Parameters>
        <Parameter />
        <Parameter />
        <Parameter />
    </Parameter>

    <ServiceManifestImport>
        <ServiceManifestRef ServiceManifestVersion="1.2.3">
    </ServiceManifestImport>

    <ServiceManifestImport>
        <ServiceManifestRef ServiceManifestVersion="1.2.3">
    </ServiceManifestImport>

    ...

For the scenario here with multiple attributes XPath can also help you. The query for the ServiceManifestVersion would look like //sf:ServiceManifestRef/@ServiceManifestVersion. Notice the two slashes //. In XPath this means select multiple nodes.

Hopefully this gave you a good idea about the usage of XmlPoke in Cake!