ASP.NET MVC4：IQueryable不包含“添加”的定义

I have tried to make an MVC news system. I started by the use a pluralsight tutorial which was used to create a department with employees. I changed the idea to fit my own purposes, changing the departments to "category" and employees to "newspost". This all works out fine, but now I want to remove the categories, since I don't need categories for my news system. But I can't add to the database using entityframework when I do this.

我试图建立一个MVC新闻系统。我开始使用一个复数教程，用于创建一个有员工的部门。我改变了想法以适应我自己的目的，将部门改为“类别”，将员工改为“新闻报道”。这一切都很好，但现在我想删除类别，因为我不需要我的新闻系统的类别。但是当我这样做时，我无法使用entityframework添加到数据库中。

I have an interface for the datasource that looks like this:

我有一个数据源接口，如下所示：

INewMvcSiteDataSource

INewMvcSiteDataSource

public interface INewMvcSiteDataSource
{
    IQueryable<NewsPost> NewsPosts { get; }

    void Save();
}

This is inherited by my DB Context class:

这是我的DB Context类继承的：

NewMvcSiteDb

NewMvcSiteDb

public class NewsMvcSiteDb : DbContext, INewMvcSiteDataSource
{
    public NewsMvcSiteDb() : base("DefaultConnection")
    {
    }

    public DbSet<NewsPost> NewsPosts { get; set; }

    IQueryable<NewsPost> INewMvcSiteDataSource.NewsPosts
    {
        get { return NewsPosts; }
    }

    public void Save()
    {
        SaveChanges();
    }
}

I then want to use it in the controller to add a newspost to the database:

然后我想在控制器中使用它来向数据库添加新闻帖：

NewsController

NewsController

var newsPost = new NewsPost()
                    {
                        Subject = newsModel.Subject,
                        Content = newsModel.Content,
                        ImagePath = newsModel.ImagePath
                    };
_db.NewsPosts.Add(newsPost);
_db.Save();

But this is where the ADD fails with the message: 'System.Linq.IQueryable' does not contain a definition for 'Add' and no extension method 'Add' accepting a first argument of type 'System.Linq.IQueryable' could be found (are you missing a using directive or an assembly reference?)

但这是ADD失败的消息：'System.Linq.IQueryable'不包含'Add'的定义，也没有扩展方法'Add'接受第一个类型'System.Linq.IQueryable'的参数可以找到（您是否缺少using指令或程序集引用？）

Now as the error says, its caused by using IQueryable, but I have no idea how else to do it.

现在正如错误所说，它是由使用IQueryable引起的，但我不知道如何做到这一点。

Can you guys help?

你们能帮忙吗？

Thanks.

谢谢。

1 个解决方案

#1

If you don't mind exposing DbSet via your interface (some people don't like the ORM bleeding into the application),you should be able to do the following:

如果你不介意通过你的界面暴露DbSet（有些人不喜欢ORM流入应用程序），你应该能够做到以下几点：

public interface INewMvcSiteDataSource
{
    DbSet<NewsPost> NewsPosts { get; }

    void Save();
} 



public class NewsMvcSiteDb : DbContext, INewMvcSiteDataSource
{
    public NewsMvcSiteDb() : base("DefaultConnection")
    {
    }

    public DbSet<NewsPost> NewsPosts { get; set; }

    public void Save()
    {
        SaveChanges();
    }
}