ASP.NET Core Web App .NET 6, reading configuration from within a Razor pages' cs file

Question

I'm trying to find a simple way to access a value from the configuration of a .NET 6, ASP.NET Core Web App, in a Razor page's .cs file, using Visual Studio 2022. There's a lot of examples of how to do this online the old way. I'm trying to get up to speed with ASP.NET Core, and .NET 6, and I don't want to use the old techniques.

Right now I can connect to a SQLite database with a very simple configuration. Here's the code in my Index.cshtml.cs file,

using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.RazorPages;
using Microsoft.Extensions.Configuration;
using System.Data.SQLite;

namespace Something.Pages
{
    public class IndexModel : PageModel
    {
        private readonly ILogger<IndexModel> _logger;

        public IndexModel(ILogger<IndexModel> logger)
        {
            _logger = logger;
        }

        public void OnGet()
        {
            var cnnStrBuilder = new SQLiteConnectonStringBuilder();
            cnnStrBuild.DataSource = "DBFile.SQLite";
            using (SQLiteConnection cnn = new(cnnStrBuilder.ConnectionString))
            {
                cnn.Open();
                ...
            }
        }
    }
}

This works. I can read and display data without the need for a DBContext, or EntityFramework, or anything else. All I want to change is to get the connection string from the appsettings.json file. My appsettings.json looks like this,

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning"
    }
  },
  "ConnectionStrings": {
    "MyConStr" : "DBFile.SQLite"
  },
  "AllowedHosts": "*"
}

in my Program.cs file is the builder object, which I could use to get the configuration.

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.
builder.Services.AddRazorPages();

var app = builder.Build();

// Configure the HTTP request pipeline.
if (!app.Environment.IsDevelopment())
{
    app.UseExceptionHandler("/Error");
}

app.UseHttpsRedirection();
app.UseStaticFiles();
app.UseRouting();
app.UseAuthorization();
app.MapRazorPages();
app.Run();

but how do I get access to the builder object in the Razor page's .cs file so I can get to the configuration? .NET 6 is supposed to make things like this easier, I thought. BTW, I purposefully left 'connection string' out of the title of this post because I feel like this should be a generic thing. It shouldn't be so hard to retrieve a string value from the configuration settings from anywhere in the application. What am I missing?

Answer 1

You can inject an instance of IConfiguration in your PageModel which you can use to access appsettings.json values.

public class IndexModel : PageModel
{
    private readonly ILogger<IndexModel> _logger;
    private readonly IConfiguration _configuration;

    public IndexModel(ILogger<IndexModel> logger, IConfiguration configuration)
    {
        _logger = logger;
        _configuration = configuration;
    }

    public void OnGet()
    {
        var cnnStrBuilder = new SQLiteConnectonStringBuilder();
        cnnStrBuild.DataSource = _configuration.GetConnectionString("MyConStr");
        using (SQLiteConnection cnn = new(cnnStrBuilder.ConnectionString))
        {
            cnn.Open();
            ...
        }
    }
}

You can also check this article for more info: https://www.learnrazorpages.com/configuration/