Factory/Singleton pattern in Azure Functions

run.csx

public class StartUpWork {
    private static StartUpWork _singleton;
    private string initializeOnce;

    public StartUpWork() {
        // Do long startup tasks/create database connection pools/whatever you want to happen once
        this.initializeOnce = "Woooooo!";
    }

    public static StartUpWork ensureStartUp() {
        if(StartUpWork._singleton == null) {
            StartUpWork._singleton = new StartUpWork();
        }
        return StartUpWork._singleton;
    }
}

public static void Run(HttpWebRequest req) {
    StartUpWork.ensureStartUp();
    // Do the rest of your thing/access properties on StartUpWork
}