Learn how to fetch properties or values from appsettings.json in .NET Core Razor Pages and console projects, using both IConfiguration and Options Patterns.

All projects are Razor Pages except two console project. The majority of work is done with dependency injection.

Warning
This article is not a step-by-step on how to work with appsettings.json so if that is what you are looking for you may be disappointed. The intent is to provide working code samples to learn from.

Update September 2024

Added an example for working with Excel.

First steps

• If you are new to dependency injection see Dependency injection in ASP.NET Core
• Decide what to place in appsettings.json
• Do the values change will determine which interface to use.
• Examine include soure code
• Read Microsoft documentation, see the resource section at end of this article.
• Get stuck, ask on Stackoverflow

What not to store

• User names and passwords
• Any sensitive information that may compromise data and/or the company. This may also include connection strings to databases unless protected by a DMZ for instance.

Not included

Working with vaults.

Environments

For working with different environments see Use multiple environments in ASP.NET Core which will assist a developer learning how to work with multiple environments. I see no reason to repeat good documentation.

Also see project EnvironmentApplication

Projects

Take time to review these projects, more likely than not there will be a solution to what a developer needs to store and read data.

• VariousMethodsApplication smorgasbord of code samples for obtaining information from appsettings.json
  • Index page: demonstrates how to read nested sections using IOptions and IOptionsSnapshot
  • ApplicationFeaturesLoose page: demonstrates IConfiguration.Bind while in ApplicationFeaturesStrong the same section is accessed using IOptionsSnapshot which is a better option if the application needs to get fresh values if the appsetting.json file changes.
  • GetSectionExample page: provides sample code to read a section in appsettings.json
  • NamedOption page variations on the Index Page
  • OptionsMonitorExample page IOptionsMonitor code sample. Note there seems to be issues with the OnChange event.
• ConnectionStringApplication is a simple example to get a connection string from appsettings.json for EF Core and using a data provider, in this case Microsoft.Data.SqlClient.
• ConnectionStringApplication1 is a simple example to get a connection string from appsettings.json for Microsoft.Data.SqlClient with a setting in appsettings.json to handle connection timeout.
• ControlLoggingApplication Example to toggle SeriLog on/off via appsettings.json
• DataAnnotatedValidationApplication shows how to validate values in appsettings.json using Data Annotations validation in Program.cs
• ReadListApplication example for reading an array/list
• ReadSettingsConsoleApplication sinple console project for showing reading settings from appsettings.json
• SectionExistsApplication demonstrates how to check if a section exists in appsettings.json
• EnvironmentApplication demonstrates reading a connection string dependent on the current environment.
• UpdaterApplication how to update appsettings.json at runtime
• MiniApplication get connection string in minimal project.
• GetWebAddressesApplication the idea is to show a developer might store web addresses for services in appsettings.json
• DependencyInjectionConsoleApplication robust console project for appsettings.json and dependency injection
• HybridApplication reads a connection string from appsettings.json to read application settings from SQL-Server table using json columns. Data operations are in the class project Hybrid.Core

Secrets

See the following article ASP.NET Core/Razor pages Secret Manager with source code in the following repository in the following project.

Requires

• Microsoft Visual Studio 2022 or higher
• .NET Core 7

What’s the difference between IOptionsMonitor vs. IOptionsSnapshot?

The major difference is the lifetime of these instances. IOptionsMonitor is registered as Singleton, whereas the IOptionsSnapshot is registered as Scoped.

• Use IOptions, when you are not expecting your configuration values to change.
• Use IOptionsSnapshot when you expect your values to change, but want them to be uniform for the entire request cycle.
• Use IOptionsMonitor when you need real-time options data.

Resources

• Configuration in ASP.NET Core
• Options pattern in ASP.NET Core
• Use multiple environments in ASP.NET Core

Source code

Clone the following GitHub repository.