带有Android c＃Cant的Entity Framework Core无法找到MigrateAsync

Question

I am trying to create an entity framework example using a class library in .net c# xamrain for android but I am having an issue with an example I am following.

 var dbFolder = System.Environment.GetFolderPath(System.Environment.SpecialFolder.Personal);
 var fileName = "dbappoitnemtns.db";
 var dbFullPath = Path.Combine(dbFolder, fileName);
 try
   {
      using (var db = new BookingContext(dbFullPath))
      {
         await db.Database.MigrateAsync(); //We need to ensure the latest Migration was added. This is different than EnsureDatabaseCreated.

       Appointments _appTestDate1 = new Appointments() { Subject="Test Appointment           
     1",StarDate=DateTime.Now,EndDate=DateTime.Now.AddHours(2),isActive=true };                 

      }
      catch (Exception ex)
     {
           System.Diagnostics.Debug.WriteLine(ex.ToString());
      }

The issue I am having is that it cant find MigrateAsync() My Context is as follows

using BookingDataAccess.Models;
using Microsoft.EntityFrameworkCore;

namespace BookDataContext
{
   public class BookingContext : DbContext
{
    public DbSet<Appointments> Appointment { get; set; }

    private string DatabasePath { get; set; }

    public BookingContext()
    {

    }

    public BookingContext(string databasePath)
    {
        DatabasePath = databasePath;
    }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.UseSqlite($"Filename={DatabasePath}");
    }
 }
}

And my class is as follows I do not no what I missing as to why it cannot find MirgrateAsync I am using the following packages.

<ItemGroup>
    <PackageReference Include="Microsoft.EntityFrameworkCore">
      <Version>2.0.2</Version>
    </PackageReference>
    <PackageReference Include="Microsoft.EntityFrameworkCore.Sqlite.Core">
      <Version>2.0.2</Version>
    </PackageReference>
    <PackageReference Include="Xamarin.Android.Support.v7.AppCompat" Version="25.*" />
  </ItemGroup>

This is my source code to see if someone can see anything that I could be missing in terms of a reference I am using the latest versions of ef core and sql lite.

Also where is best practise to place the database creation code can this be done in the context I am following this example which placed it in the main activity some how I do not believe that this is the best place for it.

I am trying to follow this example which is a year old also what is the best way to get my migrations in. https://blog.xamarin.com/building-android-apps-with-entity-framework/

This is my full source if anyone could be able to tell me whats wrong also does sql express 2016 have an offline sync mode yet ?. I persume a web service is the best way to go.

https://github.com/davidbuckleyni/andriodapp

Answer 1

The issue I am having is that it cant find MigrateAsync() My Context is as follows

The method Migrate and MigrateAsync exists in an extension class called RelationalDatabaseFacadeExtensions , which included in Microsoft.EntityFrameworkCore .

So, you just need to import this namespace:

using Microsoft.EntityFrameworkCore;

namespace BookingApp{
    ...
}

Then you can use it.