3221226107 (0xc000027b) API REST

Krzysztof 0 Reputation points


I am a novice programmer. Does anyone know how to solve the problem with 3221226107 (0xc000027b).

Well, after replacing the code in TodoListPage.xaml.cs


public partial class TodoListPage : ContentPage

    public TodoListPage()




public partial class TodoListPage : ContentPage
    ITodoService _todoService;

    public TodoListPage(ITodoService todoService)

        _todoService = todoService;


in AppShell.xaml, TodoListPage cannot be selected

        ContentTemplate="{DataTemplate local:TodoListPage}"
        Route="TodoListPage" />

What causes startup error generates error 3221226107 (0xc000027b)

I found a description of the solution for this error on the throne


But after adding further code in MauiProgram.cs

namespace R4;

public static class MauiProgram
    public static MauiApp CreateMauiApp()
        var builder = MauiApp.CreateBuilder();
            .ConfigureFonts(fonts =>
                fonts.AddFont("OpenSans-Regular.ttf", "OpenSansRegular");
                fonts.AddFont("OpenSans-Semibold.ttf", "OpenSansSemibold");

        //// don't forget to register both the page _and_ the ViewModel
        builder.Services.AddTransient<Services.IRestService, Services.RestService>();
        builder.Services.AddTransient<Services.ITodoService, Services.TodoService>();

        return builder.Build();


error 3221226107 (0xc000027b) appears.

Can anyone help me?

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  1. Leon Lu (Shanghai Wicresoft Co,.Ltd.) 64,006 Reputation points Microsoft Vendor


    I still have a problem with loading the data. Can anyone tell me how to load data into the list?

    I test your API, your Json data have only one record. And your Json properties are different from your TodoItem.

    Firstly, please change your name of property in the TodoItem like following code.

     public class TodoItem    {
            public int userId { get; set; }
            public int id { get; set; }
            public string title { get; set; }
            public string body { get; set; } 

    After that, you will get some errors about Error    CS1061    'TodoItem' does not contain a definition for 'ID', please change these properties from TodoItem.

    Then, open your public async Task<List<TodoItem>> RefreshDataAsync() method in RestService.cs. Based on your API, you just have only one record. You should change Items = JsonSerializer.Deserialize<List<TodoItem>>(content, _serializerOptions); to

     Items.Add(System.Text.Json.JsonSerializer.Deserialize<TodoItem>(content, _serializerOptions));

    In the end, please change the binding value from name to title in your TodoListPage

    <Label Text="{Binding title}"    VerticalTextAlignment="Center" />

    By the way, if you want to add other records in your API. Such as following Json.

      "userId": 1,  "id": 4,  "title": "this is title1",  "body": "test data"
      "userId": 2,  "id": 4,  "title": "this is title2",  "body": "test data"

    You can use following code to deserialize JSON data in public async Task<List<TodoItem>> RefreshDataAsync() method of RestService.cs.

        //if you have several records in API, you could deserialize to List<TodoItem>
        Items=System.Text.Json.JsonSerializer.Deserialize<List<TodoItem>>(content, _serializerOptions);

    Best Regards,

    Leon Lu

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