使用System.Data.SQLite和Entity Framework 6的简单示例

Question

I am trying to get a simple code first example to work in a console app using SQLite and EF6, however I am running into multiple errors: I created a new console project in VS 2015. Then install EF (6.1.3) and System.Data.SQLite (1.0.102) via NuGet.

Try to run a simple program:

namespace SQLiteConsole1
{
    class Person
    {
        public int Id { get; set; }
        public string Name { get; set; }
    }

    class MyContext : DbContext
    {
        public DbSet<Person> Persons { get; set; }
    }

    class Program
    {
        static void Main(string[] args)
        {
            using (var db = new MyContext())
            {
                var person = new Person() { Name = "John" };
                db.Persons.Add(person);
                db.SaveChanges();
            }
        }
    }
}

This is what my App.Config looks like this:

  <connectionStrings>
    <add name="MyContext" connectionString="Data Source=C:\Temp\Test.sqlite" providerName="System.Data.SQLite" />
  </connectionStrings>
  <entityFramework>
    <defaultConnectionFactory type="System.Data.Entity.Infrastructure.SqlConnectionFactory, EntityFramework" />
    <providers>
      <provider invariantName="System.Data.SqlClient" type="System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer" />
      <provider invariantName="System.Data.SQLite.EF6" type="System.Data.SQLite.EF6.SQLiteProviderServices, System.Data.SQLite.EF6" />
    </providers>
  </entityFramework>
  <system.data>
    <DbProviderFactories>
      <remove invariant="System.Data.SQLite.EF6" />
      <add name="SQLite Data Provider (Entity Framework 6)" invariant="System.Data.SQLite.EF6" description=".NET Framework Data Provider for SQLite (Entity Framework 6)" type="System.Data.SQLite.EF6.SQLiteProviderFactory, System.Data.SQLite.EF6" />
    <remove invariant="System.Data.SQLite" /><add name="SQLite Data Provider" invariant="System.Data.SQLite" description=".NET Framework Data Provider for SQLite" type="System.Data.SQLite.SQLiteFactory, System.Data.SQLite" /></DbProviderFactories>
  </system.data>

When I first run this program I get the following error:

Unhandled Exception: System.InvalidOperationException: No Entity Framework provider found for the ADO.NET provider with invariant name 'System.Data.SQLite'. Make sure the provider is registered in the 'entityFramework' section of the application config file."

So I change <provider invariantName="System.Data.SQLite.EF6" to <provider invariantName="System.Data.SQLite" , then I get this error:

Unhandled Exception: System.Data.Entity.Infrastructure.DbUpdateException: An error occurred while updating the entries. See the inner exception for details. System.Data.Entity.Core.UpdateException: An error occurred while updating the entries. See the inner exception for details. System.Data.SQLite.SQLiteException: SQL logic error or missing database no such table: People

What needs to be changed to get this simple example working?

Answer 1

A similar question is asked over here: Entity Framework 6 with SQLite 3 Code First - Won't create tables

kjbartel gives very useful explanation that table creation is not supported by the EF SQLite Driver.

Also see https://github.com/msallin/SQLiteCodeFirst , which provides an excellent solution. I installed the SQLite.CodeFirst NuGet package, and added the below code, then the app works fine:

    class MyContext : DbContext
    {
        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            var sqliteConnectionInitializer = new SqliteCreateDatabaseIfNotExists<MyContext>(modelBuilder);
            Database.SetInitializer(sqliteConnectionInitializer);
        }
        public DbSet<Person> Persons { get; set; }
    }

Answer 2

You need to initialize your database with the tables for your models. Notice the error "SQL logic error or missing database no such table: People".

That means you need to run SQL to create the corresponding tables in the database, thankfully, if using VS, under the context menu while in the model editor (*.edmx files), there is an option to have it auto-generate the SQL and execute it to create the table entries in the database for you based on the model. Note: sometimes the auto-generated for non MS-SQL can have issues that need to be manually fixed before it will compile/run.