我可以在ASP.NET Core启动期间访问数据库吗？

Question

I have recently been working on a .NET Core web API. I have just attempted authentication using JWT, by following the guide on https://stormpath.com/blog/token-authentication-asp-net-core .

All was going well until I had to replace the hard-coded username and passwords in the GetIdentity method with a DB query and realized I do not know how to access the DB from within this file!

The method I am referring to is shown in the link below on line 70. https://github.com/nbarbettini/SimpleTokenProvider/blob/master/test/SimpleTokenProvider.Test/Startup.Auth.cs

My questions are as follows.

1. Can I access the database here? If so how?
2. Should this be where the GetIdentity method is, or is there a better way?

Answer 1

Yes, you can access the database! Code that runs in the Configure method can access any services that are added in the ConfigureServices method, including things like database contexts.

For example, if you have a simple Entity Framework context:

using Microsoft.EntityFrameworkCore;
using SimpleTokenProvider.Test.Models;

namespace SimpleTokenProvider.Test
{
    public class SimpleContext : DbContext
    {
        public SimpleContext(DbContextOptions<SimpleContext> options)
            : base(options)
        {
        }

        public DbSet<User> Users { get; set; }
    }
}

And you add it in ConfigureServices :

services.AddDbContext<SimpleContext>(opt => opt.UseInMemoryDatabase());

Then, you can access it when you are setting up the middleware:

var context = app.ApplicationServices.GetService<SimpleContext>();

app.UseSimpleTokenProvider(new TokenProviderOptions
{
    Path = "/api/token",
    Audience = "ExampleAudience",
    Issuer = "ExampleIssuer",
    SigningCredentials = new SigningCredentials(signingKey, SecurityAlgorithms.HmacSha256),
    IdentityResolver = (username, password) => GetIdentity(context, username, password)
});

And rewrite the GetIdentity method a little:

private Task<ClaimsIdentity> GetIdentity(SimpleContext context, string username, string password)
{
    // Access the database using the context
    // Here you'd need to do things like hash the password
    // and do a lookup to see if the user + password hash exists
}

I'm the author of the original sample. Sorry it wasn't clear initially! I tried to write the IdentityResolver delegate in a way that makes it easy to provide your own functionality -- like integrating with your own database (as above), or hooking it up to ASP.NET Core Identity. Of course, you're free to throw away my code and do something better, too. :)

Answer 2

On .NET CORE 2.1, just pass the context as an argument to the Configure method:

public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory, YourDbContext context)
{
        //do whatever you want with the context here...
}

Answer 3

The accepted answer does not work for scoped services ( scoped services are created per request, if you are using Entity Framework and adding the context with AddDbContext then this is the case ).

You can use scoped services in startup as follows ( source ):

// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    using (var serviceScope = app.ApplicationServices.CreateScope())
    {
        var services = serviceScope.ServiceProvider;
        var myDbContext = services.GetService<MyDbContext>();
    }
}

or pass it in the argument of the Configure method as shown in the answer of juanora

Answer 4

I might be wrong on some other level but the solution I found is to create a scope.

I passed the app instead of the ctx in GetIdentity, then in GetIdentity using a scope:

using (var serviceScope = app.ApplicationServices.GetRequiredService<IServiceScopeFactory>().CreateScope()) {
    if (serviceScope.ServiceProvider.GetService<YourAppDbContext>() != null) 
    {
      var ctx = serviceScope.ServiceProvider.GetService<YourAppDbContext>();

      if (AnAuthenticateMethodHereMaybe(ctx, username, password)) {
        return Task.FromResult(new ClaimsIdentity(new 
GenericIdentity(username, "Token"), new Claim[] { }));
      }
    }
  }