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Keeping Configuration Settings in Memory

In an earlier column, I showed how to access configuration settings in your project's appsettings.json file and then make those settings available throughout your application as IOptions objects.

But you don't have to use the appsettings.json file if you don't want to -- .NET Core will let you hard-code your configuration settings or retrieve them from some other source (a database, perhaps). Wherever you get your settings from, you can still bundle them up as IOptions objects to share with the rest of your application. And your application will neither know nor care where those configuration settings come from.

Typically, you'll retrieve your settings in your project's Startup class (in the Startup.cs file), specifically in the class's ConfigureServices method. If you're not using appsettings.json, creating an IOptions object is a three-step process.

First, you'll need to define a Dictionary and load it with keys that identify your configuration settings and values (the actual settings). That code looks like this:

var settings = new Dictionary<string, string> 
        {  
            {"toDoService:url", "http://..."},  
            {"toDoService:contractid", "???"}   
        }; 

For my keys, I've used two-part names with each part separated by a colon (:). This lets me organize my configuration settings into sections. My example defined a section called toDoService with two settings: url and contracted.

The second step is to create a ConfigurationBuilder, add my Dictionary of configuration settings to it and use that ConfigurationBuilder to build an IConfiguration object. This IConfiguration object is similar to the one automatically passed to your ConfigureService method except, instead of being tied to the appsettings.json file, this one is tied to that Dictionary of settings.

Here's that code:

var cfgBuilder = new ConfigurationBuilder();
cfgBuilder.AddInMemoryCollection(settings);
IConfiguration cfg = cfgBuilder.Build();

The fourth, and final, step is to add an IOptions object to your application's services collection from your own IConfiguration object:

services.Configure(cfg.GetSection("toDoService"));

Now, as I described in that earlier article, you can use that IOptions<toDoSettings> object anywhere in your application just like an IOptions object built from your appsettings.json file.

Posted by Peter Vogel on 03/26/2019 at 8:42 AM


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