Xamarin Forms Android实体框架核心的suresureCreated无法正常工作

Question

这是我的代码：

public class ApplicationContext : DbContext
    {           
        private const string databaseName = "Database.db";
        public DbSet<Setting> Setting { get; set; }       
        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            String databasePath = "";
            switch (Device.RuntimePlatform)
            {
                case Device.iOS:
                    SQLitePCL.Batteries_V2.Init();
                    databasePath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments), "..", "Library", databaseName); ;
                    break;
                case Device.Android:
                    databasePath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Personal), databaseName);                    
                    break;
                case Device.WPF: {
                        databasePath = Path.Combine(Environment.CurrentDirectory, databaseName);
                        break;
                    }
                default:
                    throw new NotImplementedException("Platform not supported");
            }
            if (!File.Exists(databasePath))
            {
                File.Create(databasePath);
            }
            optionsBuilder.UseSqlite($"Filename={databasePath}");
        }
    }
public class Setting
    {
        [Key]
        public string Key { get; set; }

        public string Value { get; set; }
    }

在WPF中，一切运行良好。

但是，在Android中，即使我以前使用EnsureCreated，它也始终报告“没有这样的表”错误。

这是怎么了？我该如何解决？谢谢。

Answer 1

请确保您安装了正确的nuget软件包：

我用您的代码编写了一个演示，在我这方面效果很好，这是我的代码：

public partial class MainPage : ContentPage
{
    public MainPage()
    {
        InitializeComponent();

        ApplicationContext context = new ApplicationContext();
        context.Database.EnsureCreated();


        Task.Run (async () => {

            var newPosts = new Setting() { Key = "123", Value = "test" };
            context.Setting.Add(newPosts);


            var result = context.Setting.Where(X => X.Key == "123").FirstOrDefault();

            Console.WriteLine(result.Value);
        } );


    }
}

public class ApplicationContext : DbContext
{
    private const string databaseName = "Database.db";
    public DbSet<Setting> Setting { get; set; }
    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        String databasePath = "";
        switch (Device.RuntimePlatform)
        {
            case Device.iOS:
                SQLitePCL.Batteries_V2.Init();
                databasePath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments), "..", "Library", databaseName); ;
                break;
            case Device.Android:
                databasePath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Personal), databaseName);
                break;
            case Device.WPF:
                {
                    databasePath = Path.Combine(Environment.CurrentDirectory, databaseName);
                    break;
                }
            default:
                throw new NotImplementedException("Platform not supported");
        }
        if (!File.Exists(databasePath))
        {
            File.Create(databasePath);
        }
        optionsBuilder.UseSqlite($"Filename={databasePath}");
    }
}
public class Setting
{
    [Key]
    public string Key { get; set; }

    public string Value { get; set; }
}

我上传了测试项目here，随时可以问我任何问题。