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Initialize Singleton variable in Startup and use it in whole app

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User-1629310966 posted

I want to store data in an object and I want to use this in the whole app. I created an Object and register as Singleton in Program.cs

Object:

private Dictionary<string, string> _currentValues; public Dictionary<string, string> currentValues { get => _currentValues; set { _currentValues = value; StateHasChanged(); } }

Singleton Registration:

services.AddSingleton<LocalizeData>();

In program.cs after registration I added initial data.

var _localizeData = host.Services.GetRequiredService<LocalizeData>(); _localizeData.currentValues = locaData;

Now I want to use these data in the whole app. I injected it in each page in which I want to use the data

@LocalizeData localizeData

If I use now localizeData.currentValues the object is null.

What is missing. How can I initialize an object in Starttup and how can I use the data in whole app?
Monday, April 5, 2021 8:10 PM

Answers

User475983607 posted

Below is an Blazor WASM example.

Service

    public interface ISingletonServiceDemo
    {
        Dictionary<string, string> currentValues { get; set; }
    }

    public class SingletonServiceDemo : ISingletonServiceDemo
    {
        private readonly ILogger<SingletonServiceDemo> _logger;
        private Dictionary<string, string> _currentValues;
        public SingletonServiceDemo(ILogger<SingletonServiceDemo> logger)
        {
            _logger = logger;
            _currentValues = new Dictionary<string, string>();
        }

        public Dictionary<string, string> currentValues
        {
            get => _currentValues;
            set
            {
                _currentValues = value;
                _logger.LogInformation("The entire dictionary was set");
            }
        }
    }

public class Program
{
    public static async Task Main(string[] args)
    {
        var builder = WebAssemblyHostBuilder.CreateDefault(args);
        builder.RootComponents.Add<App>("#app");

        builder.Logging.SetMinimumLevel(LogLevel.Debug);

        builder.Services.AddScoped(sp => new HttpClient
        {
            BaseAddress = new Uri(builder.HostEnvironment.BaseAddress)
        });

        builder.Services.AddSingleton<ISingletonServiceDemo, SingletonServiceDemo>();
        var host = builder.Build();

        ISingletonServiceDemo service = host.Services.GetRequiredService<ISingletonServiceDemo>();
        Dictionary<string, string> dic = new Dictionary<string, string>();
        dic.Add("Hello", "World");
        service.currentValues = dic;

        await host.RunAsync();
    }
}

Implementation

@page "/"
@inject BlazorWasmDemo.Services.ISingletonServiceDemo service


Welcome to your new app.

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

<div>
    @service.currentValues["Hello"]
</div>

Marked as answer by Anonymous Thursday, October 7, 2021 12:00 AM

Monday, April 5, 2021 10:01 PM

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Initialize Singleton variable in Startup and use it in whole app

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