Организация Entity Framework Core Add-Migration Throws «Элемент с той же ключом уже был добавлен. ⇐ C#

[Anonymous]

У меня есть база данных SQL Server с EF Core в моем проекте, и я хочу добавить таблицу и столбец в другую таблицу. Но когда я запускаю add-migration < /code> в консоли PM, я получаю эту ошибку < /p>

An item with the same key has already been added. Key: MyProject.Model.MyContext

, где myproject - мой основной проект ASP.NET, а MyContext - мой класс dbContext. < /p>

Мой класс dbcontext выглядит как < /p>

namespace MyProject.Model
{
public class MyContext : DbContext
{
public MyWorker Worker { get; private set; }

///
/// initialize the worker instance to get the crud methods of the database
///
public MyContext()
{
Worker = new MyWorker(this);
}

public static string GetConnectionString()
{
return Startup.ConnectionString;
}

///
/// Our own context must override the OnConfiguring Method from Ef Core to set the right connection
/// Connectionstring is set in appsettings.json
///
///

protected override void OnConfiguring(DbContextOptionsBuilder _builder)
{
_builder.UseSqlServer(GetConnectionString());
}

protected override void OnModelCreating(ModelBuilder _modelBuilder) {
_modelBuilder.Entity().HasIndex(u => u.MailAdress).IsUnique();
}

public DbSet Projects { get; set; }
public DbSet Documents { get; set; }
public DbSet DocsData { get; set; }
public DbSet Users { get; set; }
public DbSet Systems { get; set; }
}

public class DesignTimeContextFactory : IDesignTimeDbContextFactory
{
public MyContext CreateDbContext(string[] args)
{
IConfiguration configuration = new ConfigurationBuilder()
.SetBasePath(Directory.GetCurrentDirectory())
.AddJsonFile("appsettings.json")
.Build();

var builder = new DbContextOptionsBuilder();

var connectionString = configuration["Connectionstrings:MyConnection"];

return new MyContext();
}
}
}



Таблица для добавления - это таблица Systems и два столбца, которые нужно добавить в документах Таблица.

с флагом -вербозе < /code> я получаю следующий выход < /p>

PM> Add-Migration Update -verbose
Using project 'MyProject'.
Using startup project 'MyProject'.
Build started...
Build succeeded.
C:\Program Files\dotnet\dotnet.exe exec --depsfile D:\Development\Project\MyProject\MyProject\bin\Debug\netcoreapp2.2\MyProject.deps.json --additionalprobingpath C:\Users\chris\.nuget\packages --additionalprobingpath "C:\Program Files\dotnet\sdk\NuGetFallbackFolder" --runtimeconfig D:\Development\Project\MyProject\MyProject\bin\Debug\netcoreapp2.2\MyProject.runtimeconfig.json C:\Users\chris\.nuget\packages\microsoft.entityframeworkcore.tools\2.2.4\tools\netcoreapp2.0\any\ef.dll migrations add Update --json --verbose --no-color --prefix-output --assembly D:\Development\Project\MyProject\MyProject\bin\Debug\netcoreapp2.2\MyProject.dll --startup-assembly D:\Development\Project\MyProject\MyProject\bin\Debug\netcoreapp2.2\MyProject.dll --project-dir D:\Development\Project\MyProject\MyProject\ --language C# --working-dir D:\Development\Project\MyProject --root-namespace MyProject
Using assembly 'MyProject'.
Using startup assembly 'MyProject'.
Using application base 'D:\Development\Project\MyProject\MyProject\bin\Debug\netcoreapp2.2'.
Using working directory 'D:\Development\Project\MyProject\MyProject'.
Using root namespace 'MyProject'.
Using project directory 'D:\Development\Project\MyProject\MyProject\'.
Finding DbContext classes...
Finding IDesignTimeDbContextFactory implementations...
Found IDesignTimeDbContextFactory implementation 'DesignTimeContextFactory'.
Found DbContext 'MyContext'.
Found IDesignTimeDbContextFactory implementation 'DesignTimeContextFactory'.
Found DbContext 'MyContext'.
System.ArgumentException: An item with the same key has already been added. Key: MyProject.Model.MyContext
at System.Collections.Generic.Dictionary`2.TryInsert(TKey key, TValue value, InsertionBehavior behavior)
at Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.FindContextTypes()
at Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.FindContextType(String name)
at Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.CreateContext(String contextType)
at Microsoft.EntityFrameworkCore.Design.Internal.MigrationsOperations.AddMigration(String name, String outputDir, String contextType)
at Microsoft.EntityFrameworkCore.Design.OperationExecutor.AddMigrationImpl(String name, String outputDir, String contextType)
at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.c__DisplayClass3_0`1.b__0()
at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.Execute(Action action)
An item with the same key has already been added. Key: MyProject.Model.MyContext


Подробнее здесь: https://stackoverflow.com/questions/561 ... has-alread