Initialize Singleton variable in Startup and use it in whole app[Answered] RSS

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  vetsoftone

  Member

  1 Points

  1 Post

  Initialize Singleton variable in Startup and use it in whole app

  Apr 05, 2021 08:10 PM|vetsoftone|LINK

  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?

• • Reply
  mgebhard

  All-Star

  53661 Points

  24018 Posts

  Re: Initialize Singleton variable in Startup and use it in whole app

  Apr 05, 2021 10:01 PM|mgebhard|LINK

  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");
              }
          }
      }

  Register

  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>