无法实现IDbContextFactory用于实体框架数据迁移 [英] Unable to implement IDbContextFactory for use with Entity Framework data migrations

问题描述

试图实现 IDbContextFactory 如下。并在行上得到以下错误，返回Create（options.ContentRootPath，options.EnvironmentName）; 和 var optionsBuilder = new DbContextOptionsBuilder< MyProjContext>（）; 在运行以下 PM 命令

  PM> ;添加迁移MyMigration -context MyProjContext 
  

错误

在启动类启动中调用方法ConfigureServices时出错。考虑在设计时使用IDbContextFactory来覆盖DbContext的初始化。错误：在程序集'ef，Version = 1.0.0.0，Culture = neutral，PublicKeyToken = adb9793829ddae60'上找不到UserSecretsIdAttribute。
System.InvalidOperationException：找不到名为MyProjContext的连接字符串。 ....

注意 MyProjCnotext.cs 和 MyProjContextFactory.cs 文件位于 MyProj\Models 文件夹

MyProjContextFactory类

  public class MyProjContextFactory：IDbContextFactory< MyProjContext> 
 {
 public MyProjContext Create（）
 {
 var environmentName = Environment.GetEnvironmentVariable（Hosting：Environment）; 
 return Create（Directory.GetCurrentDirectory（），environmentName）; 
} 
 
 public MyProjContext Create（DbContextFactoryOptions options）
 {
 return Create（options.ContentRootPath，options.EnvironmentName）; 
 
 
 public MyProjContext Create（string basePath，string environmentName）
 {
 var builder = new ConfigurationBuilder（）
 .SetBasePath（basePath）
 .AddJsonFile（appsettings.json）
 .AddJsonFile（$appsettings。{environmentName} .json，true）
 .AddEnvironmentVariables（）; 
 
 var Configuration = builder.Build（）; 
 
 var connectionName = nameof（MyProjContext）; 
 var connectionString = Configuration.GetConnectionString（connectionName）; 
 if（String.IsNullOrWhiteSpace（connectionString）== true）
 throw new InvalidOperationException（$无法找到名为{connectionName}的连接字符串。 
 
 // init SQL server 
 var optionsBuilder = new DbContextOptionsBuilder< MyProjContext>（）; 
 optionsBuilder.UseSqlServer（connectionString）; 
 
返回新的MyProjContext（optionsBuilder.Options）; 
} 
} 
  

MyProjContext.cs / p>

 命名空间MyProj.Models 
 {
 public class MyProjContext：DbContext 
 {
 public MyProjContext（DbContextOptions< MyProjContext>选项）：base（options）
 {
 
} 
 public DbSet< Table1> Table1 {get;组; } 
 public DbSet< Table2> Table2 {get;组; } 
 ... 
} 
} 
  

解决方案

你抛出一个异常： throw new InvalidOperationException（$找不到一个名为{connectionName}的连接字符串）;

添加到appsettings.json和appsettings.Development.json：

  {
 ... 
ConnectionStrings：{
MyProjContext：...
} 
} 
  / pre> 
Tried to implement IDbContextFactory as follows. And got the following error at lines return Create(options.ContentRootPath, options.EnvironmentName); and var optionsBuilder = new DbContextOptionsBuilder<MyProjContext>(); when running following PM command
PM> add-migration MyMigration -context MyProjContext
Error

  
An error occurred while calling method 'ConfigureServices' on startup class 'Startup'. Consider using IDbContextFactory to override the initialization of the DbContext at design-time. Error: Could not find 'UserSecretsIdAttribute' on assembly 'ef, Version=1.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60'.
  System.InvalidOperationException: Could not find a connection string named 'MyProjContext'. ....
Note Both MyProjCnotext.cs and MyProjContextFactory.cs files are are in MyProj\Models folder

MyProjContextFactory class
public class MyProjContextFactory : IDbContextFactory<MyProjContext>
{
    public MyProjContext Create()
    {
        var environmentName = Environment.GetEnvironmentVariable("Hosting:Environment");
        return Create(Directory.GetCurrentDirectory(), environmentName);
    }

    public MyProjContext Create(DbContextFactoryOptions options)
    {
        return Create(options.ContentRootPath, options.EnvironmentName);
    }

    public MyProjContext Create(string basePath, string environmentName)
    {
        var builder = new ConfigurationBuilder()
            .SetBasePath(basePath)
            .AddJsonFile("appsettings.json")
            .AddJsonFile($"appsettings.{environmentName}.json", true)
            .AddEnvironmentVariables();

        var Configuration = builder.Build();

        var connectionName = nameof(MyProjContext);
        var connectionString = Configuration.GetConnectionString(connectionName);
        if (String.IsNullOrWhiteSpace(connectionString) == true)
            throw new InvalidOperationException($"Could not find a connection string named '{connectionName}'.");

        // init SQL server
        var optionsBuilder = new DbContextOptionsBuilder<MyProjContext>();
        optionsBuilder.UseSqlServer(connectionString);

        return new MyProjContext(optionsBuilder.Options);
    }
}
MyProjContext.cs
namespace MyProj.Models
{
public class MyProjContext : DbContext
{
    public MyProjContext(DbContextOptions<MyProjContext> options) : base(options)
    {

    }
    public DbSet<Table1> Table1 { get; set; }
    public DbSet<Table2> Table2 { get; set; }
    ...
}
}

解决方案
You threw an exception: throw new InvalidOperationException($"Could not find a connection string named '{connectionName}'.");

Add in appsettings.json and appsettings.Development.json:
{
    ...
    "ConnectionStrings": {
        "MyProjContext": "..."
    }
}


                        
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