带有 ASP.NET Core 3.0 和 EF Core 的多租户应用程序

Question

我正在开发一个基于多租户的应用程序，该应用程序将为每个学校/租户提供一个单独的数据库。每个模式将彼此相同。这个想法是使用 .NET Core 3 和 EF Core 拥有一个数据库上下文。

例如，客户端导航到 school1.gov.uk，然后使用存储在 appsettings.json 中“school1”下的连接字符串实例化 SchoolContext。

目前，我必须针对添加的每个新上下文运行 add-migration。任何人都可以想出一个解决方案来在单个上下文（即 SchoolContext ）下运行一次迁移吗？

主要上下文

public class SchoolContext : DbContext
{     protected readonly IConfiguration _configuration;
      private readonly IHttpContextAccessor _httpContextAccessor;

    public DbSet<Student> Students { get; set; }
    public DbSet<Course> Courses { get; set; }

    public SchoolContext(IConfiguration configuration, IHttpContextAccessor httpContextAccessor) 
    {
        _configuration = configuration;
        _httpContextAccessor = httpContextAccessor;
    }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
            var subdomain = _httpContextAccessor.HttpContext.Request.Host.Host;
            var connectionString = _configuration.GetConnectionString(subdomain);
            optionsBuilder.UseSqlServer(connectionString);
    }

} 

租户上下文 1

public class School1Context : SchoolContext
{
    public Schoo1Context()
    {

    }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
         var connectionString = _configuration.GetConnectionString("School1");
         optionsBuilder.UseSqlServer(connectionString);
    }

} 

租户上下文 2

public class School2Context : SchoolContext
{
    public School2Context()
    {

    }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
         var connectionString = _configuration.GetConnectionString("School2");
         optionsBuilder.UseSqlServer(connectionString);
    }

} 

程序.cs

         using (var scope = host.Services.CreateScope())
         {
             var school1Context = scope.ServiceProvider.GetService<School1Context>();
             school1Context.Database.Migrate();
             var school2Context = scope.ServiceProvider.GetService<School2Context>();
             school2Context.Database.Migrate();
         }

Appsettings.json

"ConnectionStrings": {
    "School1": "Persist Security Info=true;Data Source=.\\SQLEXPRESS;Initial Catalog=School1;User ID=;Password=;",
    "School2": "Persist Security Info=true;Data Source=.\\SQLEXPRESS;Initial Catalog=School2;User ID=;Password=;",

   }

Answer 1

我遇到了与您几乎相同的问题。我有一个 TenantDbContext。

public class TenantDbContext : DbContext
{
    private readonly Tenant _tenant;

    public DbSet<Branch> Branches { get; set; }

    public TenantDbContext(DbContextOptions<TenantDbContext> options, IHttpContextAccessor httpContextAccessor)
        : base(options)
    {
        if (httpContextAccessor.HttpContext != null)
        {
            _tenant = (Tenant)httpContextAccessor.HttpContext.Items["TENANT"];
        }
    }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        if (_tenant != null)
        {
            optionsBuilder.UseSqlServer(_tenant.ConnectionString);
        }

        base.OnConfiguring(optionsBuilder);
    }
}

然后我发现使用包管理器控制台很难“添加迁移”，因为连接字符串是动态的，所以我在 Startup.ConfigureServices() 中为连接字符串创建了一个占位符（“Dev”）

var devConnectionString = _config.GetConnectionString("Dev");
services.AddDbContext<TenantDbContext>(opt => opt.UseSqlServer(devConnectionString));

要知道，配置 DbContext 有两种方法，分别如上面的两个代码片段所示。如果两者都提供，将首先调用 AddDbContext()，然后另外调用 OnConfiguring()。

当您运行“Add-Migration”命令时，将在 DbContext 中使用占位符连接字符串生成迁移，尽管没有指定租户。当您运行应用程序时，您只需添加一个中间件并调用 Migrate() 将这些迁移应用到您的租户数据库，然后再转到 MVC 中间件。

public class TenantIdentifier
{
    private readonly RequestDelegate _next;
    private readonly IConfiguration _configuration;
    private readonly IHttpContextAccessor _httpContextAccessor;

    public TenantIdentifier(RequestDelegate next, IConfiguration configuration, IHttpContextAccessor httpContextAccessor)
    {
        _next = next;
        _configuration = configuration;
        _httpContextAccessor = httpContextAccessor;
    }

    public async Task Invoke(HttpContext httpContext, HostDbContext hostDbContext)
    {
        // Get tenant id from token
        var tenantId = httpContext.User.FindFirst(Constants.TENANT)?.Value;

        // Set tenant id to httpContext.Items
        if (!string.IsNullOrWhiteSpace(tenantId))
        {
            var tenant = hostDbContext.Tenants.SingleOrDefault(t => t.Id.ToString() == tenantId);
            httpContext.Items["TENANT"] = tenant;

            using(var tenantDbContext = new TenantDbContext(new DbContextOptions<TenantDbContext>(), _httpContextAccessor))
            {
                tenantDbContext.Database.Migrate();
            }
        }

        await _next.Invoke(httpContext);
    }
}

然后，您只需要运行一次“Add-Migration”，根本不需要创建占位符数据库。