如何从任何 class blazor 服务器端读取 appsetting.json

Question

i know how to acess to appsetting.json fron razor component but how from any class in a blazor serverside project?

from razor component i simply inject:

@inject IConfiguration _config

and access all that i need like: _config.GetConnectionString("default")

but how can do the same from any class? when i try to do

IConfiguration _config;

it says when i want to reach data that _config is null or is an unassigned local variable depands where i write the variable.

Answer 1

• first, you should create custom config model

    public class PositionOptions
    {
        public const string Position = "Position";

        public string Title { get; set; }
        public string Name { get; set; }
    }

• then, register config model in startup.cs

services.Configure<PositionOptions>(Configuration.GetSection(PositionOptions.Position));

• don not forget appsetting.json

 "Position": {
    "Title": "Editor",
    "Name": "Joe Smith"
  }

• at last, inject ioptions in the index.razor

@page "/"
@using WebApplication.Model
@using Microsoft.Extensions.Options
@inject IOptions<PositionOptions> _options
<h1>Hello, world!</h1>

Welcome to your new app.

<h1>@_options.Value.Title</h1>
<h1>@_options.Value.Name</h1>

<SurveyPrompt Title="How is Blazor working for you?"/>

Answer 2

I get the connection string details from appsettings.json in a class file. Please try this below code:

Test.cs

public void GetAddSettingDetails(){
            var appsettingsJsonString = File.ReadAllText("appsettings.json");
            var appsettingsJObject = JObject.Parse(appsettingsJsonString);
            var connectionstring = appsettingsJObject.SelectToken("DefaultConnection").Value<string>();
}

appsettings.json

{
  "AllowedHosts": "*",
  "DefaultConnection": "Data Source=*****;Initial Catalog=Test;User Id=aabbcc;Password=aabbccdd;",
  "ApplicationVersion": "1.0.0",
}

Answer 3

i understood how it work so i can answer my question myself

in fact, you just have to add a constructor in your class with Iconfiguration as argumentand you can use it and call your data stored in your app setteing:

    public class MyClass 
{
    public MyClass (IConfiguration config)
    {
        _config = config;
    }


    private readonly IConfiguration _config;
    


    void MyMethod(){
            .....
           }
}

You can use it after in your method:

string myCon = _config.GetConnectionString("Default");

Answer 4

This is just a complement to @khalidAb and @KenTsu answers perhaps you find it useful. I usually work this way. Like KenTsu mentioned, it is just an implementation of Options pattern, he did it for a Blazor component, this is just for any class.

appSettings.json

"PositionOptions": {
    "Title": "Editor",
    "Name": "Joe Smith"
}

Startup.cs

services.Configure<PositionOptions>(Configuration.GetSection(nameof(PositionOptions)));

Model

public class PositionOptions
{
    public string Title { get; set; }
    public string Name { get; set; }
}

Any class

public class AnyClass {
    private readonly PositionOptions _positionOptions;

    public MyClass(IOptions<PositionOptions> positionOptions)
    {
        _positionOptions = positionOptions.Value;
    }

    public Get()
    {
        string title = _positionOptions.Title;
    }
}