Featcher

Feature + switcher == Featcher

Lightweight feature switching for .NET

• Uses session cookies to switch features on temporarily for testing, demo and review
• Uses custom config sections to turn things on for real when they're properly released.

var fs = new FeatureSwitcher();
if (fs.IsEnabled(Features.NewsTicker)) {
  // show the news ticker!
}

How To Define your Features

You can do everything with strings - all feature-switching methods can take a string argument which is the name of the feature.

There's a slightly nicer way to manage them, though. Create a static class in your project that exposes each of your switchable project features as a static property. Featcher doesn't restrict how you do this, but you do need an instance of Feature for each feature you want to switch.

public static class Features {
    public static Feature BigRedBox = new Feature("BigRedBox", "Shows a big red box on the landing page");
    public static Feature BigGreenBox = new Feature("BigGreenBox", "Shows a big green box on the landing page");
    public static Feature NuclearLaunch = new Feature("NuclearLaunch", "Allow users to launch nuclear missiles");

    public static Feature[] AllFeatures = {
        BigRedBox,
        BigGreenBox,
        NuclearLaunch
    };

    public static Feature Find(string name) {
        return (AllFeatures.FirstOrDefault(feature => feature.Name == name));
    }
}

This gives you enum-style intellisense for your features:

var fs = new FeatureSwitcher();

if (fs.IsEnabled(Features.BigRedBox)) {
  // do something with a big red box!
}

Temporarily Enable a Feature

You can temporarily enable features by setting cookies - this means developers and testers can view and test code that isn't visible to the rest of the world yet.

public ActionResult Toggle(string name, bool? enable) {
    var feature = Features.Find(name);
    if (feature != null && enable.HasValue) FeatureSwitcher.Toggle(feature, enable.Value);
	return(View());
}

This sets a session cookie.

Cookies use subkeys for individual features:

Request.Cookies["featcher"]["BigRedBox"] = true;

Permanently Enable a Feature

To launch a feature, use a custom web.config setting to switch it on permanently. Features that have been enabled via web.config cannot be disabled via cookies

<configuration>
  <configSections>
    <section name="featcher" type="Featcher.Configuration.FeatureSection, Featcher" />
  </configSections>
  <featcher>
    <feature name="BigRedBox" enabled="true" />
  </featcher>
</configuration>

Classic ASP support

Because some of our code still uses classic ASP, there's a simple function to determine whether a feature is enabled from classic ASP code.

<%@ language="JScript" %>
<%
function isFeatureEnabled(featureName) {
    try {
        // Note the use of the XPath 1.0 translate hack to make our feature name case-insensitive.
        var xpath = "/configuration/featcher/feature[translate(@name,'ABCDEFGHIJKLMNOPQRSTUVWXYZ','abcdefghijklmnopqrstuvwxyz')='" + featureName.toLowerCase() + "']";
        var config = Server.CreateObject("msxml2.DOMDocument.6.0");
        config.load(Server.MapPath("/web.config"));
        var node = config.selectSingleNode(xpath);
        var enabledAttribute = (node ? node.getAttribute("enabled") : "");
        if (enabledAttribute.toLowerCase() === "true") return (true);
    } catch (ex) {
    }
    var cookie = Request.Cookies("featcher");
    return (cookie && cookie(featureName) && cookie(featureName).toLowerCase && cookie(featureName).toLowerCase() === "true");
}
%>