エンティティフレームワークコア2.0の移行でシードデータをスローするエラーでデータベースを更新します

Question

私はEF Core 2.0コードの最初の移行を使用しています。私は新しいデータベースに移行sinを実行しようとしています。私はシードデータを使用しています。シードデータメソッドをコメントアウトすると、シードデータを使用してもエラーは表示されません。問題が何であるか分かりません。誰でも助けてくれますか？

エラー：

System.Data.SqlClient.SqlException (0x80131904): There is already an object named 'WorkflowBranches' in the database.

テーブルが作成されますが、レコードが、私は約5移行スクリプトを持っているにもかかわらず、migrationhistoryテーブルに表示されていません。また、シードデータが挿入されます。

I think the database is getting created twice. I am using migrations script and also in the seed method, there is dbContext.Database.EnsureCreatedAsync(). This could be the reason but i am not sure.

Startup.cs：

public void ConfigureServices(IServiceCollection services) 
{ 
    //Other code 
    services.AddTransient<DbSeeder>(); 
} 

public void Configure(IApplicationBuilder app, 
         IHostingEnvironment env, 
         DbSeeder dbSeeder) 
{ 
    app.UseMvc(); 

    dbSeeder.SeedAsync(app.ApplicationServices).Wait(); 
} 

DbSeeder.cs：

using Workflow.Models; 
using Microsoft.EntityFrameworkCore; 
using Microsoft.Extensions.DependencyInjection; 
using Microsoft.Extensions.Logging; 
using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Threading.Tasks; 

namespace Workflow.DBContext 
{ 
    public class DbSeeder 
    { 
     readonly ILogger _Logger; 

     public DbSeeder(ILoggerFactory loggerFactory) 
     { 
      _Logger = loggerFactory.CreateLogger("DbSeederLogger"); 
     } 

     public async Task SeedAsync(IServiceProvider serviceProvider) 
     { 
      //Based on EF team's example at https://github.com/aspnet/MusicStore/blob/dev/samples/MusicStore/Models/SampleData.cs 
      using (var serviceScope = serviceProvider.GetRequiredService<IServiceScopeFactory>().CreateScope()) 
      { 
       var dbContext = serviceScope.ServiceProvider.GetService<WorkflowDBContext>(); 
       if (await dbContext.Database.EnsureCreatedAsync()) 
       { 
        if (!await dbContext.Alert.AnyAsync()) 
        { 
         await InsertAlertsSampleData(dbContext); 
        } 
       } 
      } 
     } 

     public async Task InsertAlertsSampleData(WorkflowDBContext dbContext) 
     { 
      //Insert Risktypes 
      var riskTypes = GetRiskTypes(); 
      dbContext.RiskType.AddRange(riskTypes); 

      try 
      { 
       int numAffected = await dbContext.SaveChangesAsync(); 
       _Logger.LogInformation($@"Saved {numAffected} riskTypes"); 
      } 
      catch (Exception exp) 
      { 
       _Logger.LogError($"Error in {nameof(DbSeeder)}: " + exp.Message); 
       throw; 
      } 

      //Insert categories 
      var categories = GetCategories(riskTypes); 
      dbContext.Category.AddRange(categories); 

      try 
      { 
       int numAffected = await dbContext.SaveChangesAsync(); 
       _Logger.LogInformation($"Saved {numAffected} categories"); 
      } 
      catch (Exception exp) 
      { 
       _Logger.LogError($"Error in {nameof(DbSeeder)}: " + exp.Message); 
       throw; 
      } 

      //var alerts = GetAlerts(categories); 
     } 

     private List<Alert> GetAlerts(List<Category> categories) 
     { 
      return new List<Alert>(); 
     } 

     private List<RiskType> GetRiskTypes() 
     { 
      var riskTypes = new List<RiskType> 
      { 
       new RiskType { Name = "Risk1"}, 
       new RiskType { Name = "Risk2"} 
      }; 

      return riskTypes; 
     } 

     private List<Category> GetCategories(List<RiskType> riskTypes) 
     { 
      var categoryList = new List<Category>(); 

      var categories = new string[] 
      { 
       "Category1Risk1", 
       "Category2Risk1", 
       "Category3Risk1", 
       "Category1Risk2" 
      }; 

      //Low Risk 
      foreach (var category in categories.Take(3)) 
      { 
       categoryList.Add(new Category 
       { 
        Name = category, 
        RiskType = riskTypes.FirstOrDefault(rt=>rt.Name=='Risk1') 
       }); 
      } 

      //High Risk 
      foreach (var category in categories.Skip(3)) 
      { 
       categoryList.Add(new Category 
       { 
        Name = category, 
        RiskType = riskTypes.FirstOrDefault(rt=>rt.Name=='Risk2') 
       }); 
      } 

      return categoryList; 
     } 
    } 
} 

おかげ

Answer 1

あなたはEfのコア2.0である場合は、このkwnoする必要があります：

を

In 2.0 projects using EF Core 2.0, Program.BuildWebHost is invoked to obtain the application services. Unlike 1.x, this has the additional side effect of invoking Startup.Configure. If your 1.x app invoked database initialization code in its Configure method, unexpected problems can occur. For example, if the database doesn't yet exist, the seeding code runs before the EF Core Migrations command execution. This problem causes a dotnet ef migrations list command to fail if the database doesn't yet exist. Consider the following 1.x seed initialization code in the Configure method of Startup.cs:

app.UseMvc(routes => 
{ 
    routes.MapRoute(
     name: "default", 
     template: "{controller=Home}/{action=Index}/{id?}"); 
}); 

SeedData.Initialize(app.ApplicationServices); 

In 2.0 projects, move the SeedData.Initialize call to the Main method of Program.cs:+

var host = BuildWebHost(args); 

using (var scope = host.Services.CreateScope()) 
{ 
    var services = scope.ServiceProvider; 

    try 
    { 
     // Requires using RazorPagesMovie.Models; 
     SeedData.Initialize(services); 
    } 
    catch (Exception ex) 
    { 
     var logger = services.GetRequiredService<ILogger<Program>>(); 
     logger.LogError(ex, "An error occurred seeding the DB."); 
    } 
} 

host.Run(); 

As of 2.0, it's bad practice to do anything in BuildWebHost except build and configure the web host. Anything that is about running the application should be handled outside of BuildWebHost — typically in the Main method of Program.cs.

今日、私はこのコードのために私のコードを変更し、MI液が正常に働いていました。他のポストで

https://docs.microsoft.com/en-us/aspnet/core/migration/1x-to-2x/#move-database-initialization-code