Develop Reference

Unable to create database

When running my program I get this exception: 'Microsoft.Data.Sqlite.SqliteException: 'SQLite Error 1: 'no such table: Tasks'.'
I followed the steps on the Microsoft docs to install EFcore, create the model and create the database. This did the trick on one of my other Maui projects but not on this one since I can't get it to to create the table 'Tasks'.
using Microsoft.EntityFrameworkCore;
using Task = Todo.Models.Task;
namespace Todo.Data
{
class TaskContext : DbContext
{
public DbSet<Task> Tasks { get; set; }
public string DbPath { get; }
public TaskContext()
{
var folder = Environment.SpecialFolder.LocalApplicationData;
var path = Environment.GetFolderPath(folder);
DbPath = System.IO.Path.Join(path, "ToDo.db");
}
// The following configures EF to create a Sqlite database file in the
// special "local" folder for your platform.
protected override void OnConfiguring(DbContextOptionsBuilder options)
=> options.UseSqlite($"Data Source={DbPath}");
}
}
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
namespace Todo.Models
{
public class Task
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int Id { get; set; }
public string Title { get; set; }
public bool IsCompleted { get; set; }
}
}
Edit: Adding Database.EnsureCreated() in the TaskContext constructor fixed it

EF Core: entity requires a key - but it does have a key

I'm using EF Core and have the following project structure
AppName.Entity
Alert
Other classes
AppName.Repository
AlertRepository
Other Repository classes
The alert entity is as follows:
using System;
using System.ComponentModel.DataAnnotations;
namespace AppName.Entity
{
public class Alert
{
[Key]
public int AlertId { get; set; }
public string RuleId { get; set; }
public string DeviceId { get; set; }
public string VehicleVin { get; set; }
public string AlertText { get; set; }
public DateTime DateTimeUtc { get; set; }
public AlertCategory AlertCategory { get; set; }
}
public enum AlertCategory
{
VehicleHealth = 1,
FleetHealth = 2,
EmissionsHealth = 3,
Fuel = 4,
AssetUtilization = 5,
Safety = 6,
DutyCycle = 7
}
}
AlertRepository.cs is as follows:
using AppName.Entity;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
namespace AppName.Repository
{
public class AlertRepository// : GenericRepository<Alert>, IAlertRepository
{
public async Task<int> Save(Alert alert)
{
using (AFIdbContext context = new AFIdbContext())
{
context.Alerts.Add(alert);
await context.SaveChangesAsync();
return alert.AlertId;
}
}
public async Task<bool> Save(IEnumerable<Alert> alerts)
{
using (AFIdbContext context = new AFIdbContext())
{
foreach (Alert alert in alerts)
{
context.Alerts.Add(alert);
}
await context.SaveChangesAsync();
return true;
}
}
public IQueryable<Alert> GetList(DateTime fromDate, DateTime toDate, int pageSize, int pageNum)
{
using (AFIdbContext context = new AFIdbContext())
return context.Alerts.Where(x => x.DateTimeUtc >= fromDate && x.DateTimeUtc <= toDate).Skip(pageSize * pageNum).Take(pageSize);
}
}
}
AFIdbContext.cs
using AppName.Entity;
using Microsoft.EntityFrameworkCore;
using System.Configuration;
namespace AppName.Repository
{
public class AFIdbContext : DbContext
{
private string _afiConnstring;
public string AFIConnstring
{
get
{
if (_afiConnstring != null)
return _afiConnstring;
else
return "";
}
}
public AFIdbContext() : base()
{
}
public AFIdbContext(DbContextOptions<AFIdbContext> options) : base(options)
{
}
public DbSet<Alert> Alerts { get; set; }
public DbSet<User> Users { get; set; }
public DbSet<UserAlertPreference> UserAlertPreferences { get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<AlertRepository>().ToTable("Alert");
modelBuilder.Entity<User>().ToTable("User");
modelBuilder.Entity<UserAlertPreference>().ToTable("UserAlertPreference");
}
protected override void OnConfiguring(DbContextOptionsBuilder options)
{
options.UseSqlServer(AppExtensions.ConnString);
}
}
}
When I attempt to save a collection of Alerts, I get the following exception:
System.InvalidOperationException: 'The entity type 'AlertRepository' requires a primary key to be defined. If you intended to use a keyless entity type call 'HasNoKey()'.'
The Alert entity does have a primary key in the DB and does have the [Key] attribute. Why is it telling me that the AlertRepository object doesn't have the key set when it's an Alert Entity I am trying to save? Can I not have the Entity in a separate project? I'm trying to follow a DDD pattern
The exception is being thrown before it even tries to save the records
(I have a breakpoint on await context.SaveChangesAsync(); in AlertRepository
The solution here doesn't help because I already have those set

AlertRepository is not right class to be an entity, you just have to map the Alert entity in OnModelCreating
Replace
modelBuilder.Entity<AlertRepository>().ToTable("Alert");
with
modelBuilder.Entity<Alert>().ToTable("Alert")
or you can just remove this line because entity framework will create a table for you with same name as your entity.

You have mapped the wrong entity in your OnModelCreating for table Alert.
Try with
modelBuilder.Entity<Alert>().ToTable("Alert")

How can I use context in Entity Framework?

I made Entity models in MVC, in model first approach, and I would like to know, how to insert, delete, and modify data.
I try to use
namespace EntityFrameworkModelFirst
{
using System;
using System.Data.Entity;
using System.Data.Entity.Infrastructure;
public partial class ModelFirstContainer : DbContext
{
public ModelFirstContainer()
: base("name=ModelFirstContainer")
{
}
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
throw new UnintentionalCodeFirstException();
}
public virtual DbSet<Department> DepartmentSet { get; set; }
public virtual DbSet<Employee> EmployeeSet { get; set; }
}
using (var context = new ModelFirstContainer())
{
// Perform data access using the context
}
}
But, it makes error to me. The error is: The contextual word 'var' may only appear within a local variable declaration or in script code, and missing ;.
Is it valid now? Where can i do this? Which files?
Thank you

Your using block must be in a method. You can't have it outside of a method. Also, I've removed your OnModelCreating which would have thrown an exception.
using System;
using System.Data.Entity;
using System.Data.Entity.Infrastructure;
namespace EntityFrameworkModelFirst
{
public partial class ModelFirstContainer : DbContext
{
public ModelFirstContainer() : base("name=ModelFirstContainer")
{
}
public virtual DbSet<Department> DepartmentSet { get; set; }
public virtual DbSet<Employee> EmployeeSet { get; set; }
}
public class SomeClass
{
public void DoSomeStuff()
{
using (var context = new ModelFirstContainer())
{
// Perform data access using the context
}
}
}
}
A using block is used with IDisposable objects to ensure they get properly disposed. ModelFirstContainer inherits from DbContext which implements IDisposable.

A tutorial on how to work with the Entity Framework DbContext can be found here: Working with DbContext
public class ProductContext : DbContext
{
public DbSet<Category> Categories { get; set; }
public DbSet<Product> Products { get; set; }
}
using (var context = new ProductContext())
{
// Perform data access using the context
}

Create database in App_Start

I have an solution with 2 projects, one domain class and one webUI.
In the domain class I have 2 models, a db context and a databas initializer.
List.cs:
namespace Todo.Domain
{
public class List
{
public int ListID { get; set; }
public string Day { get; set; }
public ICollection<Task> Tasks { get; set; }
}
}
Task.cs:
namespace Todo.Domain
{
public class Task
{
public int TaskID { get; set; }
public int ListID { get; set; }
public string TodoTask { get; set; }
}
}
EFDbContext.cs:
namespace Todo.Domain
{
public class EFDbContext : DbContext
{
public EFDbContext() : base("TodoList") { }
public DbSet<List> Lists { get; set; }
public DbSet<Task> Tasks { get; set; }
}
}
Initializer:
namespace Todo.Domain
{
public class TodoDbInit : System.Data.Entity.DropCreateDatabaseIfModelChanges<EFDbContext>
{
protected override void Seed(EFDbContext context)
{
var list = new List<List>
{
new List { Day="Måndag" }
};
list.ForEach(s => context.Lists.Add(s));
context.SaveChanges();
var task = new List<Task>
{
new Task { TodoTask="Fisk" }
};
task.ForEach(s => context.Tasks.Add(s));
context.SaveChanges();
}
}
}
Now, when I start my application, I want the database to be created. I have placed a setInitializer Global.asax:
namespace Todo.WebUI
{
public class MvcApplication : System.Web.HttpApplication
{
protected void Application_Start()
{
Database.SetInitializer(new TodoDbInit());
AreaRegistration.RegisterAllAreas();
RouteConfig.RegisterRoutes(RouteTable.Routes);
}
}
}
When I run my application, the database Is not created. I don't know why. Have I done something wrong?

You must make a call against your database in one of your controllers in order for it to be created (creation is on-demand). If you wish to manually create the database on application start see the answer posted here: Entity Framework code first, isn't creating the database
The following code is only setting the initializer that you wish to use against your database.
Database.SetInitializer(new TodoDbInit());
In order for it to actually be used you will need to create and access entities of your db context.

Creating a MVC4-Controller using Entity Framework

Hey Guys I hava a question. I know questions like this are asked often, but I worked on a solution for several hours and read many answers but I couldnt find the right one. I am doing an application using ASP.NET MVC 4 Razor. I´m rather new to this system. I created a .edmx Data Model using Entity Framework 5 (Database-First Approach). This is how my auto-generated Context class looks like:
namespace KSM3.Models
{
using System;
using System.Data.Entity;
using System.Data.Entity.Infrastructure;
using System.Data.Objects;
using System.Data.Objects.DataClasses;
using System.Linq;
public partial class kontrollsystemEntities : DbContext
{
public kontrollsystemEntities()
: base("name=kontrollsystemEntities")
{
}
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
throw new UnintentionalCodeFirstException();
}
[EdmFunction("kontrollsystemEntities", "udf_GetReportsByController")]
public virtual IQueryable<udf_GetReportsByController_Result> udf_GetReportsByController(string controller_account)
{
var controller_accountParameter = controller_account != null ?
new ObjectParameter("controller_account", controller_account) :
new ObjectParameter("controller_account", typeof(string));
return ((IObjectContextAdapter)this).ObjectContext.CreateQuery<udf_GetReportsByController_Result>("[kontrollsystemEntities].[udf_GetReportsByController](#controller_account)", controller_accountParameter);
}
}
}
and my Model class looks like this:
namespace KSM3.Models
{
using System;
public partial class udf_GetReportsByController_Result
{
public int ID { get; set; }
public string ProviderID { get; set; }
public int VertragID { get; set; }
public System.DateTime Leistungszeitraum_von { get; set; }
public System.DateTime Leistungszeitraum_bis { get; set; }
public string ReportklasseID { get; set; }
public int Version { get; set; }
public string Status { get; set; }
}
}
When I now click on "Add Controller" and select my classes, I get the error message:
"Unable to retrieve Metadata for KSM3.Models.udf_GetReportsByController_Result.cs"
Note: I am using Entity Framework to retrieve information from a user-defined function, not from a table! If I try the same procedure with a table, it works!
What do I have to prepare or change in order to make this work?
Thank you for all answers!

I have solved my problem, thanks!
I had to call the udf_GetReportsByController(string controller_account) method in the controller and hand the IQueryable-Result to my view.
My Controller looks like these (Note: Beginner´s mistake)
public class ReportController : Controller
{
private kontrollsystemEntities db = new kontrollsystemEntities();
//
// GET: /Report/
public ActionResult Index()
{
IQueryable<udf_GetReportsByController_Result> result = db.udf_GetReportsByController(User.Identity.Name);
return View(result.ToList());
}
}
}