TIP - Silverlight - InitParams and ApplicationLifeTimeService(s)

I have this love-hate relationship with InitParams

Pre-download values to Silverlight, so it’s available to the client before Silverlight even starts rendering
Don’t have to worry about whether Silverlight can talk to any data source - if you can’t see the webpage then the problem is elsewhere

Dislike

Well it’s on the web page… anyone could see it, and probably tweak it via DOM manipulation
If you bind to this data, you can’t really “update” it if the data changes on the server. If say the user settings has changed, you’ll need a F5 refresh to force the Silverlight client to reload. In a sense this is often treated like read-only data.

One thing we can fix

A really large App.Current with lots of different values sucked out from the initParams during App_Start

Using ApplicationLifeTimeServices

1. Write a Lifetime Service

public class CompanyApplicationLifeTimeService : IApplicationService
{
    static CompanyApplicationLifeTimeService \_current = null;

    public static CompanyApplicationLifeTimeService Current
    {
        get
        {
            return \_current;
        }
    }

    #region IApplicationService Members

    public void StartService(ApplicationServiceContext context)
    {            
        \_current = this;
        var parseThisStuff = context.ApplicationInitParams;
    }

    public void StopService()
    {
        \_current = null;
    }

    #endregion
}

.csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, “Courier New”, courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }

2. Add this to your App.Xaml

<Application.ApplicationLifetimeObjects> <common:CompanyApplicationLifeTimeService x:Name=“CompanyLifeTimeService” /> </Application.ApplicationLifetimeObjects> <Application.Resources> …

3. Now anywhere in your code you have access to the service Singleton

CompanyApplicationlifeTimeService.Current.GiveMeStuff

Using ApplicationLifeTimeServices

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