Like the title says, I am trying to connect a new MVC 5 app created by Visual Studio 2013 to an existing database table created by and Azure Mobile Service.
I realized that the issue was with the schema of the tables that were created by the mobile service. Instead of using the default "dbo" schema, the tables used <mobile_service_name> as the schema. My MVC project was looking for dbo.<Table_Name> instead of <mobile_service_name>.<Table_Name> and was throwing an error as a result. To fix this, you need to add some mappings in you DB Context class to tell it where exactly to find the tables it is looking for. These mappings are done in an overridden method called OnModelCreating. It ends up looking like this:
public class ApplicationDbContext : IdentityDbContext<ApplicationUser>
{
public ApplicationDbContext() : base("DefaultConnection")
{
}
public System.Data.Entity.DbSet<MyObject> MyObjects { get; set; }
protected override void OnModelCreating(System.Data.Entity.DbModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
modelBuilder.Entity<MyObject>().ToTable("<mobile_service_name>.<Table_Name>");
}
}
Related
what is the proper way to create an EF Core database on an Android/iOS device with Xamarin.Forms and EntityFrameworkCore?
I've come across the EnsureCreated vs Migrate thing and since I'm planning on changing the database structure in the future, I'd like to be able to apply those migrations to an existing database, thus I've chosen the Migrate approach.
However, when I call the Migrate method, it doesn't seem to create a database. I've managed to make it work in case I copy the pre-generated database file on the devices beforehand, but that's not what I want. Is there a way to tell EF Core to check if there's an existing database, create a new database if not, and then apply pending migrations to it?
Here's what I've done so far:
I've created a .net standard class library "Data" that will hold all my database classes (context, models, and migrations).
I've changed the TargetFramework of the "Data" project from <TargetFramework>netstandard2.0</TargetFramework> to <TargetFrameworks>netcoreapp2.0;netstandard2.0</TargetFrameworks> so I could run PMC commands on it.
I've installed these nuget packages to the "Data" project:
EntityFrameworkCore
EntityFrameworkCore.Sqlite
EntityFrameworkCore.Tools
EntityFrameworkCore.Design
I've created a database context class. I've made two constructors for it. The default one will only be used by the PMC commands for generating migrations. The other one will be used in production.
public class MyTestContext : DbContext
{
private string _databasePath;
public DbSet<Issue> Issues { get; set; }
[Obsolete("Don't use this for production. This is only for creating migrations.")]
public MyTestContext() : this("nothing.db")
{
}
public MyTestContext(string databasePath)
{
_databasePath = databasePath;
}
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
//I've also tried Filename={_databasePath} here, didn't work either
optionsBuilder.UseSqlite($"Data Source={_databasePath}");
}
}
I've created a test model class, just to have something to play with
public class Issue
{
public string Id { get; set; }
}
I created an inital migration using this command, which completed successfully:
Add-Migration Migration001 -Context MyTestContext -Output Migrations
I added a call to the Migrate method in the App.xaml.cs of my Xamarin.Forms project to test if it works.
public partial class App : Application{
//... other code
protected override async void OnStart()
{
base.OnStart();
using (var db = new MyTestContext(_dbPath))
{
try
{
db.Database.Migrate();
db.Issues.Add(new Issue
{
Id = "TestIssueId"
});
db.SaveChanges();
}
catch (Exception ex)
{
Debug.WriteLine(ex);
}
}
}
//... other code
}
The _dbPath variable contains this (on Android where I'm testing it):
Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Personal), "test.db");
After all this, I'm getting this exception:
Microsoft.Data.Sqlite.SqliteException: SQLite Error 1: 'no such table: Issues'.
I use in SQLite database in UWP. It has a few tables and is located in Assets folder and has build action marked as "Content".
Under development machine it works fine.
But after deployment to MS Windows 10 tablet it has the error
SQLite error 1 no such table Companies
It corresponds to the code
using (MobileContext db = new MobileContext())
{
companiesList.ItemsSource = db.Companies.ToList();
...
}
var createdResult = Database.EnsureCreated(); // It gives false so
I assume based on https://learn.microsoft.com/en-us/dotnet/api/microsoft.entityframeworkcore.infrastructure.databasefacade.ensurecreated?view=efcore-2.1 that database exists.
I have tried
optionsBuilder.UseSqlite("Data Source=" + ApplicationData.Current.LocalFolder.Path + #"\Mobile.db");
optionsBuilder.UseSqlite("Data Source=Mobile.db");
Any clue folk? Thanks!
P.S. I use Microsoft.EntityFrameworkCore to accees SQLite.
P.S. #2 I have tried this solution https://social.msdn.microsoft.com/Forums/en-US/1a933b13-09ee-46ec-9045-e2f567b6048c/uwp-sqlite-error-1-no-such-table-name-table?forum=wpdevelop but it does not work.
Derive from official document,
Connection strings in a UWP application are typically a SQLite connection that just specifies a local filename. They typically do not contain sensitive information, and do not need to be changed as an application is deployed. As such, these connection strings are usually fine to be left in code, as shown below. If you wish to move them out of code then UWP supports the concept of settings
public class BloggingContext : DbContext
{
public DbSet<Blog> Blogs { get; set; }
public DbSet<Post> Posts { get; set; }
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
optionsBuilder.UseSqlite("Data Source=blogging.db");
}
}
And the default path of db file is application LocalFolder. It looks like this C:\Users\vxx\AppData\Local\Packages\e045f456-27d9-4966-b639-01e2281b249f_7jxxxxxxxxxx\LocalState. If your configuration is same as above, when deploy in new machine, the content of db file is empty.
OP Update
I just commented some decorations of the class like [Table("Companies")] and [Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)] and it works now!
Is repository pattern with unit of work best fit for entity framework application?
I am creating a new asp.net mvc application and i want to use stored procedure (microsoft enterprise library) instead of Entity framework(or any other ORM).
So how can i use repository pattern with mvc application?
I have explored many tutorials but not getting expected result. Please suggest me better approach for n tier application.
You have to understand that "repository pattern" is just an idea to organize your code. I think you can still use it without any problem.
I just want to provide you an example of implementation using sql stored procedure: suppose you have to manage the classic table "Contacts".
You can create your UnitOfWork contract:
public interface IContactsRepository {
void AddContact(Contact c);
void RemoveContact(Contact c);
void UpdateContact(Contact c);
void Search(string keyword);
}
After, you can create your own implementation without using EF:
public sealed class SPContactsRepository : IContactsRepository {
// Is just an exampl.e
public void AddContact(Contact c) {
var sqlCommnad = new SqlCommand(this._connectionString);
sqlCommand.CommandText = "dbo.AddContact";
sqlCommand.CommandType = CommandType.StoredProcedure;
sqlCommand.AddParameter("Name", c.Name);
sqlCommand.Connection.Open();
sqlCommand.ExecuteNonQuery();
}
}
Hope this can help!
So just to continue what Roberto already started, your controller in the MVC app will look like this:
public class ContactsController : Controller
{
private readonly IContactsRepository _contactsRepo;
public ContactsController(IContactsRepository repo)
{
_contactsRepo = repo;
}
}
These pattern uses dependency injection(DI). There are several options for DI container. You can use Unity which is a Microsoft package that you can install via nuget package manager to your MVC web project. The install will create a UnityConfig.cs file in your App_Start folder. You can register the dependency as:
public static void RegisterComponents()
{
var container = new UnityContainer();
container.RegisterType<IContactsRepository, SPContactsRepository>();
}
And in your Global.asax.cs file inside Application_Start(), you initialize the container:
UnityConfig.RegisterComponents();
If you use EF, the DbContext is already your Unit of Work and the DbSet as your repository. Having said that, you should not create a repository that will add another layer of data abstraction. Instead, you can create, domain services.
After watching the "Enhancements to Code First Migrations: Using HasDefaultSchema and ContextKey for Multiple Model Support" section of Julie Lerman's PluralSite video, "Entity Framework 6: Ninija Edition-What's New in EF 6" (https://app.pluralsight.com/library/courses/entity-framework-6-ninja-edition-whats-new/table-of-contents), it seems there is a way to run multiple schemas under a single database in Entity Framwork 6 using Code First Migrations...
However, based on the video you still need to these package manager commands for each project that houses a separate context:
1. enable-migrations
2. add-migration [MIGRATION NAME]
3. update-database
This is fine and good if you actually care about maintaining migrations going forward, which is not a concern of mine.
What I'd like to do is have each of my Context's initializers set to DropCreateDatabaseAlways, and when I start up my client app (in this case, an MVC site), code first will create the database for the first context used, create the tables in with the correct schema for that context, and then create the tables for the rest of the contexts with the correct schema.
I don't mind if the whole database is dropped and recreated every time I hit F5.
What is happening now is the last context that is accessed in the client app is the only context tables that are created in the database... any contexts being accessed before the last get their tables blown away.
I am currently using two contexts, a Billing context and a Shipping context.
Here is my code:
My client app is an MVC website, and its HomeController's Index method looks like this:
public ActionResult Index()
{
List<Shipping.Customer>
List<Billing.Customer> billingCustomers;
using (var shippingContext = new Shipping.ShippingContext())
{
shippingCustomers = shippingContext.Customers.ToList();
}
using (var billingContext = new Billing.BillingContext())
{
billingCustomers = billingContext.Customers.ToList();
}
}
Here is my DbMigrationsConfigurationClass and ShippingContext class for the Shipping Context:
internal sealed class Configuration : DbMigrationsConfiguration<ShippingContext>
{
public Configuration()
{
AutomaticMigrationsEnabled = false;
}
protected override void Seed(ShippingContext context)
{
}
}
public class ShippingContext : DbContext
{
public ShippingContext() : base("MultipleModelDb")
{
}
static ShippingContext()
{
Database.SetInitializer(new ShippingContextInitializer());
}
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.HasDefaultSchema("Shipping");
base.OnModelCreating(modelBuilder);
}
public DbSet<Customer> Customers { get; set; }
class ShippingContextInitializer : DropCreateDatabaseAlways<ShippingContext>
{
}
}
Likewise, here is the DbMigrationConfiguration class for the Billing Context and the BillingContext class:
internal sealed class Configuration : DbMigrationsConfiguration<BillingContext>
{
public Configuration()
{
AutomaticMigrationsEnabled = false;
}
protected override void Seed(BillingContext context)
{
}
}
public class BillingContext : DbContext
{
public BillingContext() : base("MultipleModelDb")
{
}
static BillingContext()
{
Database.SetInitializer(new BillingContextInitializer());
}
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.HasDefaultSchema("Billing");
base.OnModelCreating(modelBuilder);
}
public DbSet<Customer> Customers { get; set; }
class BillingContextInitializer : DropCreateDatabaseAlways<BillingContext>
{
}
}
based on the order that the contexts are being called in the controller's action method, whichever context is accessed last is the only context that is created... the other context is wiped out.
I feel like what I'm trying to do is very simple, yet code first migrations, as well as trying to "shoehorn" Entity Framework to represent multiple contexts as separate schemas in the same physical database seems a bit "hacky"...
I'm not that versed with migrations to begin with, so what I'm trying to do might not make any sense at all.
Any feedback would be helpful.
Thanks,
Mike
I'm working on multitenant application (ASP.NET 5 + EF7). Each tenant will have separate database. I will have one separate database for tenant account data. I have registered service for EF in startup class for this separate database. I have problem with migrations. I cant create EF migration, until tenantDbContext is registered as service with specific connection string. But this conection string must be dynamic for each tenant... Any idea please? What is the best option to manage DbContexts for tenants?
Future edit - protected override void OnConfiguring was the key how to do: Is this good solution please?
services.AddEntityFramework()
.AddSqlServer()
.AddDbContext<ApplicationDbContext>(options =>
options.UseSqlServer(Configuration["Data:DefaultConnection:ConnectionString"]));
services.AddEntityFramework()
.AddSqlServer()
.AddDbContext<TenantDbContext>();
public class TenantDbContext : IdentityDbContext<ApplicationUser>
{
public TenantDbContext() //development database with no connectionString in constructor
{
this._connectionString = "Connection String";
}
public TenantDbContext(string ConnectionString)
{
this._connectionString = ConnectionString;
}
private string _connectionString { get; set; }
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
optionsBuilder.UseSqlServer(_connectionString);
}
...etc
As I mentioned in comments I have not tried multi-tenant/multi-db myself but try the following:
You can use DbContext CreateIfNotExists() method. https://msdn.microsoft.com/en-us/library/system.data.entity.database.createifnotexists(v=vs.113).aspx
If you have a Migrations/Configuration.cs you can set AutomaticMigrationsEnabled property to false
Setting the initializer off is probably needed as well: Database.SetInitializer<DatabaseContext>(null);
Sorry without knowing more details like workflow of creating a new tenant (automatic from DB or is a screen filled out with the connection string and name etc.) I can't make more detailed suggestions. I would suggest that your data layer be quite abstracted from the context. It seems like a bad idea for developers to have to select the correct context. Hence the use of a factory.
An option is always requiring a tenant id to be passed into all service or repository methods. I'm guessing this would be in some kind of user claim available in the controller.