Cannot make migration. ef core 2.0

[daviatorstorm]

I've migrated from .NET Core 1.1 to .NET Core 2.0. Have some troubles with EF Core 2.0. I'm using multi environment. dotnet-ef command missing -e (environment) option, that is required in my project.

dotnet ef migrations add Test -c BackendContext -v

Error

Using project \Backend.csproj'.
Using startup project \Backend.csproj'.
Writing '\obj\Backend.csproj.EntityFrameworkCore.targets'...
dotnet msbuild /target:GetEFProjectMetadata /property:EFProjectMetadataFile=C:\Users\user\AppData\Local\Temp\tmpE244.tmp /verbosity:quiet /nologo \Backend.csproj
Writing '\obj\Backend.csproj.EntityFrameworkCore.targets'...
dotnet msbuild /target:GetEFProjectMetadata /property:EFProjectMetadataFile=C:\Users\user\AppData\Local\Temp\tmpE468.tmp /verbosity:quiet /nologo \Backend.csproj
dotnet build \Backend.csproj /verbosity:quiet /nologo

Build succeeded.
    0 Warning(s)
    0 Error(s)

Time Elapsed 00:00:03.33
dotnet exec --depsfile \bin\Debug\netcoreapp2.0\Backend.deps.json --additionalprobingpath C:\Users\user\.nuget\packages --additionalprobingpath "C:\Program Files\dotnet\sdk\NuGetFallbackFolder" --runtimeconfig \bin\Debug\netcoreapp2.0\Backend.runtimeconfig.json C:\Users\user\.nuget\packages\microsoft.entityframeworkcore.tools.dotnet\2.0.0\tools\netcoreapp2.0\ef.dll migrations add Test -c BackendContext --assembly \bin\Debug\netcoreapp2.0\Backend.dll --startup-assembly \bin\Debug\netcoreapp2.0\Backend.dll --project-dir \ --verbose --root-namespace Backend
Using assembly 'Backend'.
Using startup assembly 'Backend'.
Using application base \bin\Debug\netcoreapp2.0'.
Using working directory '\'.
Using root namespace 'Backend'.
Using project directory '\'.
Finding DbContext classes...
Finding IDesignTimeDbContextFactory implementations...
Finding application service provider...
Finding BuildWebHost method...
No BuildWebHost method was found on type 'Backend.Program'.
No application service provider was found.
Finding DbContext classes in the project...
Found DbContext 'BackendContext'.
Found DbContext 'LiteContext'.
Microsoft.EntityFrameworkCore.Design.OperationException: Unable to create an object of type 'BackendContext'. Add an implementation of 'IDesignTimeDbContextFactory<BackendContext>' to the project, or see https://go.microsoft.com/fwlink/?linkid=851728 for additional patterns supported at design time. ---> System.MissingMethodException: No parameterless constructor defined for this object.
   at System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor)
   at System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark)
   at System.Activator.CreateInstance(Type type, Boolean nonPublic)
   at System.Activator.CreateInstance(Type type)
   at Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.<>c__DisplayClass12_3.<FindContextTypes>b__13()
   --- End of inner exception stack trace ---
   at Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.<>c__DisplayClass12_3.<FindContextTypes>b__13()
   at Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.CreateContext(Func`1 factory)
   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.AddMigration.<>c__DisplayClass0_1.<.ctor>b__0()
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.<>c__DisplayClass3_0`1.<Execute>b__0()
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.Execute(Action action)
Unable to create an object of type 'BackendContext'. Add an implementation of 'IDesignTimeDbContextFactory<BackendContext>' to the project, or see https://go.microsoft.com/fwlink/?linkid=851728 for additional patterns supported at design time.

BackendContext

public class BackendContext : DbContext
{
     public BackendContext(DbContextOptions<BackendContext> options)
         : base(options)
     { }
}

In Startup.cs

services.AddDbContext<BackendContext>(opts =>
                opts.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));

EF Core version: 2.0
Database Provider: Microsoft.EntityFrameworkCore.SqlServer
Operating system: win10-x64
IDE: Visual Studio 2017
.NET Core SDK info:

.NET Command Line Tools (2.0.0)

Product Information:
 Version:            2.0.0
 Commit SHA-1 hash:  cdcd1928c9

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.15063
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\2.0.0\


Microsoft .NET Core Shared Framework Host



  Version  : 2.0.0

  Build    : e8b8861ac7faf042c87a5c2f9f2d04c98b69f28d

[daviatorstorm]

Found a solution

[ajcvickers]

@daviatorstorm Updating an ASP.NET Core application from 1.1 to 2.0 is covered by this doc: https://docs.microsoft.com/en-us/aspnet/core/migration/1x-to-2x/

It would be great if you could comment on the doc with any issues you ran into that are not covered by the guide.

[Sweetog]

@ajcvickers Hi, thanks the your the link you shared (https://docs.microsoft.com/en-us/aspnet/core/migration/1x-to-2x/). But this article does not give a single example of implementing IDesignTimeDbContectFactory<>

[cbmek]

@Sweetog look at paragraph dotnet ef database update and there is a comment:

In order for the EF Migrations tooling to work you MUST NAME THE METHOD: BuildWebHost just like the example ... you cannot use a different method name.

So you just need to update your Program.cs to:

    public class Program
    {
        public static void Main(string[] args)
        {
            BuildWebHost(args).Run();
        }

        public static IWebHost BuildWebHost(string[] args) =>
            WebHost.CreateDefaultBuilder(args)
                .UseStartup<Startup>()
                .Build();
    }

[Sweetog]

@cbmek But the will not fix the OP's error, the OP's error specifically states: "Add an implementation of 'IDesignTimeDbContextFactory'". In the link you provided there is no text that says "you MUST NAME THE METHOD: BuildWebHost"

[Sweetog]

@cbmek In addition, here is a recommendation to rename Program.BuildWebHost to fix another issue. I just ran EF Core 2.0 migrations against the Program.cs below and had no issues. I just really do think what you say is the problem is what the problem is for the OP, the problem that the OP has no implemented IDesignTimeDbContextFactory:

using System.IO;
using System.Reflection;
using Microsoft.AspNetCore;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Logging;

namespace Tsl.Example
{
    public class Program
    {
        public static void Main(string[] args)
        {
            FooBuildWebHost(args).Run();
        }

        /// <summary>
        /// This the magical WebHost.CreateDefaultBuilder method "unboxed"
        /// </summary>
        /// <param name="args"></param>
        /// <returns></returns>
        public static IWebHost FooBuildWebHost(string[] args)
        {
            return new WebHostBuilder()
                .UseKestrel()
                .UseContentRoot(Directory.GetCurrentDirectory())
                .ConfigureAppConfiguration((hostingContext, config) =>
                {
                    var env = hostingContext.HostingEnvironment;

                    config.AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
                        .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true, reloadOnChange: true);

                    if (env.IsDevelopment())
                    {
                        var appAssembly = Assembly.Load(new AssemblyName(env.ApplicationName));
                        if (appAssembly != null)
                        {
                            config.AddUserSecrets(appAssembly, optional: true);
                        }
                    }

                    config.AddEnvironmentVariables();

                    if (args != null)
                    {
                        config.AddCommandLine(args);
                    }
                })
                .ConfigureLogging((hostingContext, logging) =>
                {
                    logging.AddConfiguration(hostingContext.Configuration.GetSection("Logging"));
                    logging.AddConsole();
                    logging.AddDebug();
                })
                //.UseIISIntegration()
                .UseDefaultServiceProvider((context, options) =>
                {
                    options.ValidateScopes = context.HostingEnvironment.IsDevelopment();
                })
                .UseStartup<Startup>()
                .Build();
        }
    }
} 

[cbmek]

Changing Program.cs to one quoted in the article fixed the error for me. No IDesignTimeDbContextFactory needed.

Here is my context:

    public class ApplicationDbContext : IdentityDbContext<ApplicationUser, ApplicationRole, string>
    {
        public DbSet<SomeEntity> SomeEntities { get; set; }

        public ApplicationDbContext(DbContextOptions options) : base(options) {}
    }

Scenario 1 - old way of Program.cs

    public class Program
    {
        public static void Main(string[] args)
        {
            IWebHost host = WebHost.CreateDefaultBuilder(args)
                .UseStartup<Startup>()
                .Build();

            host.Run();
        }
    }

...and migration (I use -s because I have all my DB stuff in separate project):

Scenario2 - new way of Project.cs

Just one change here:

    public class Program
    {
        public static void Main(string[] args)
        {
            BuildWebHost(args).Run();
        }

        public static IWebHost BuildWebHost(string[] args) =>
            WebHost.CreateDefaultBuilder(args)
                .UseStartup<Startup>()
                .Build();
    }

...and magic happen:

[Sweetog]

@cbmek you are correct! wow and here I wasted so much time implementing IDesignTimeDbContextFactory and I was so bothered that I had to load appsettings again and none of the articles online even gave a thought about environment specific appsettings and all I need was a method named BuildWebHost

[crasshacker]

I'm having the same problem, and it's got me completely confused. My code had been working, but I suspected problems with my database so I decided to delete it and start fresh. Whereas previously I had been able to create the database (by adding a migration and updating), this process now fails. My Program.cs file has the standard "public static IWebHost BuildWebHost(string[] args)" method, but "Add-Migration InitialCreate" now displays a large stack trace indicating repeated failures to login to the database (which makes sense as it doesn't yet exist), and eventually prints this:

Error Number:4060,State:1,Class:11
An error occurred while calling method 'BuildWebHost' on class 'Program'. Continuing without the application service provider. Error: One or more errors occurred. (Cannot open database "TakHub" requested by the login. The login failed.
Login failed for user 'SNAPPY\Computer'.)
Unable to create an object of type 'ApplicationDbContext'. Add an implementation of 'IDesignTimeDbContextFactory' to the project, or see https://go.microsoft.com/fwlink/?linkid=851728 for additional patterns supported at design time.

I tried creating a IDesignTimeDbContextFactory subclass with a CreateDbContext method, which also failed (but strangely told me I could use Remove-Migration to remove the migration, even though the migration failed).

Has anyone got any ideas on what might be causing this issue? It's got me completely stuck at this point.

[Sweetog]

@crasshacker you do not need to add IDesignTimeDbContextFactory, in your Program.cs you have to have a method named "BuildWebHost":

        public static void Main(string[] args)
        {
            //you must must have a method/function name "BuildWebHost" otherwise EF Core Migrations will throw an execption that you need to have an implementation of IDesignTimeDbContextFactory
            BuildWebHost(args).Run();
        }

        public static IWebHost BuildWebHost(string[] args) =>
           WebHost.CreateDefaultBuilder(args)
               .UseStartup<Startup>()
               .Build();

[crasshacker]

Yes, as I stated in my note, "My Program.cs file has the standard "public static IWebHost BuildWebHost(string[] args)" method." It looks exactly like your example. Here's my complete Program class:

public class Program
{
public static void Main(string[] args)
{
BuildWebHost(args).Run();
}

public static IWebHost BuildWebHost(string[] args) =>
    WebHost.CreateDefaultBuilder(args)
        .UseStartup<Startup>()
        .Build();

}

I only tried creating a class inheriting from IDesignTimeDbContextFactory after I originally got the error message, but doing so didn't help. So neither the BuildWebHost method nor the IDesignTimeDbContextFactory class are working. Which is driving me crazy, as at one point in the path this was working fine, and I haven't made any changes to my database model or much of anything else.

[crasshacker]

I think I'm going to just create a new project from scratch, with the same database model classes, and see if I can use that to get a database built. Somehow I don't think I'll have much success, but I guess it's worth a try - especially as I have no other ideas on how to proceed. Sigh...

[bradley-varol]

I just deleted a db table, went to migrate and now i'm having this issue too. My Program.cs is exactly as recommended in the 1.x - 2.x docs.