EF代码第一 - 类型类型的属性

问题描述：

我有一个对象的属性类型为：

I have an object that has a property of type Type:

public ScheduledJob
{
    public int ID { get; set; }
    public Type JobType { get; set; }
    public string JobParameters { get; set; }
}

当我生成代码优先迁移时，我收到以下错误：

When I generate the code-first migrations, I get the following error:

System.ArgumentNullException: Value cannot be null.
Parameter name: key
    at System.Collections.Generic.Dictionary`2.FindEntry(TKey key)
    at System.Collections.Generic.Dictionary`2.TryGetValue(TKey key, TValue& value)
    at System.Data.Entity.ModelConfiguration.Configuration.Mapping.SortedEntityTypeIndex.Add(EdmEntitySet entitySet, EdmEntityType entityType)
    at System.Data.Entity.ModelConfiguration.Configuration.Mapping.EntityMappingService.Analyze()
    at System.Data.Entity.ModelConfiguration.Configuration.ModelConfiguration.ConfigureEntityTypes(DbDatabaseMapping databaseMapping, DbProviderManifest providerManifest)
    at System.Data.Entity.ModelConfiguration.Configuration.ModelConfiguration.Configure(DbDatabaseMapping databaseMapping, DbProviderManifest providerManifest)
    at System.Data.Entity.DbModelBuilder.Build(DbProviderManifest providerManifest, DbProviderInfo providerInfo)
    at System.Data.Entity.DbModelBuilder.Build(DbConnection providerConnection)
    at System.Data.Entity.Internal.LazyInternalContext.CreateModel(LazyInternalContext internalContext)
    at System.Data.Entity.Internal.RetryLazy`2.GetValue(TInput input)
    at System.Data.Entity.Internal.LazyInternalContext.InitializeContext()
    at System.Data.Entity.Internal.LazyInternalContext.get_CodeFirstModel()
    at System.Data.Entity.Infrastructure.EdmxWriter.WriteEdmx(DbContext context, XmlWriter writer)
    at System.Data.Entity.Migrations.Extensions.DbContextExtensions.<>c__DisplayClass1.<GetModel>b__0(XmlWriter w)
    at System.Data.Entity.Migrations.Extensions.DbContextExtensions.GetModel(Action`1 writeXml)
    at System.Data.Entity.Migrations.Extensions.DbContextExtensions.GetModel(DbContext context)
    at System.Data.Entity.Migrations.DbMigrator..ctor(DbMigrationsConfiguration configuration, DbContext usersContext)
    at System.Data.Entity.Migrations.DbMigrator..ctor(DbMigrationsConfiguration configuration)
    at System.Data.Entity.Migrations.Design.ToolingFacade.BaseRunner.GetMigrator()
    at System.Data.Entity.Migrations.Design.ToolingFacade.GetPendingMigrationsRunner.RunCore()
    at System.Data.Entity.Migrations.Design.ToolingFacade.BaseRunner.Run()

做这个场景的最好方法是什么工作？

What is the best way to make this scenario work?

为@ NSGaga的帖子编辑：

整个模型）是这样的：

所有作业对象都实现以下界面：

All job objects implement the following interface:

public interface IJob
{
    Guid ID { get; set; }
    void Run();
}

每个作业都有自己的属性用作一种参数： / p>

Each of the jobs has its own properties used as a sort of parameter:

public class ProcessMedia : IJob
{
    public Guid ID { get; set; }

    public int MediaContentID { get; set; }

    public void Run()
    {
        if(MediaContentID <= 0)
             throw new Exception("Missing parameter MediaContentID");
        //work
    }
}

我使用这个模型用于异步作业处理系统，工作正常。现在，我正在尝试构建一个调度程序，在这里我可以给它一个作业类型和参数（序列化到字符串），并且可以间隔地运行。

I use this model for an asynchronous job processing system, which works fine. Now, I'm trying to build a scheduler, where I can give it a job type and parameters (serialized to string) and have it run on intervals.

答

看看我几天前发布的这篇文章...

Take a look at this post I made few days ago...

我应如何定义可以采取各种数据类型的字段EF？

你为什么这样做？

你几乎不需要保存类型。

@David提到了已经做了什么。

@David mentioned already what to do.

但是，我进一步阻止你这样做 - 而是反思。

But I'd further discourage you to go that way - but rather rethink.

EF代码首先是关于强类型实体。你可以有很好的'继承'工作，无需保存类型。

The EF code first is about having 'strong-typed' entities. You can have nice 'inheritance' working, w/o a need to save a Type.

如果您需要某种类似枚举类型的限制＃使用枚举或int。

If you need something like an 'enum type' out of a limited # - use an enum or an int.

您可以发布您的模型，如果可以更改，我会指出。

You can post your model and I'll point you out if it could be changed.

我想你可以使用继承来满足您的需要。

创建不同类型的作业实体。

I think you could use inheritance for what you need.
Make different types of Jobs entities.

例如看看这个解决方案在这里（我的帖子）

EF代码保护区中的多个继承级别

...并且让我知道问题，当您尝试某些问题时。

e.g. take a look at this solution here (my post earlier)
Multiple Inheritance Levels in EF Code Firs
...and let me know if problems, questions when you try something.

也许它更容易使用TPH（就像在那里），它们都存储在同一张表中 - 通常你会收到较少的问题。

Maybe it's easier to use TPH (like it's in there), they all get stored in the same table - and you get less problems usually.

EF代码第一 - 类型类型的属性

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