.NET MVC剃刀的下拉列表中的外键 [英] .net mvc razor dropdowns for foreign keys

问题描述

好吧，这似乎简单，但让我目瞪口呆。

Ok, this seemed simple, but is making my head spin.

我创建的模型的基础上codeFirst。

I have created models based on CodeFirst.

public class Category
{
    public int ID { get; set; }

    [StringLength(255, MinimumLength = 1)]
    public string Name { get; set; }
}

public class SubCategory
{
    public int ID { get; set; }
    public Category category { get; set; }

    [StringLength(255, MinimumLength = 1)]
    public string Name { get; set; }
}

现在，当我自动生成控制器和视图的子类别它（开箱即用），让我创造新的子类别的对象，而无需指定类别（甚至通过它正确地创建一个外键关系的分类表数据库）。

Now when i auto-generate the controller and view for SubCategory it (out-of-the-box) lets me create new SubCategory objects without specifying the Category (even through it correctly creates a foreign key relation to the Category table in the DB).

因此​​，虽然确定我，我只是下降一个下拉的create.cshtml文件，并将其使用。

So i though ok, i'll just drop a drop down in the create.cshtml file and have it use that.

经过一些，而我成功加入该到控制器：

after some while i succeed by adding this to the controller:

    public ActionResult Create()
    {
        ViewBag.Categories = new SelectList(db.Category.ToList(),"ID","Name");
        return View();
    } 

和这对观点：

    @Html.DropDownList(model => model.category, "Categories")

但现在的对象不会自动赶上，我想用这对我的外键，所以，当我停止code在POST方法仍显示为NULL的类别字段的对象。

But now the object does not automatically catch that i want to use this for my foreign key, so when i stop the code at the POST method it still displays the object with NULL in the category field.

我想我的问题是双重的。我应该怎么做？如果我的方法是正确的，到目前为止，我在想什么？

I guess my question is twofold. How should i do this? and if my method is right so far, what am i missing?

我只是想这是保存在子类别表中的新对象包括外键类别。

I just want the new object which is saved to the SubCategory table to include the foreign key to Category.

希望这是有道理的。

推荐答案

最简单的方法是在你的定义的CategoryId 的标量属性子类别类

Easiest way is to define a scalar property named CategoryId in your SubCategory class

public class SubCategory
{
    public int ID { get; set; }

    public int CategoryID { get; set; }
    public Category category { get; set; }

    [StringLength(255, MinimumLength = 1)]
    public string Name { get; set; }
}

然后正确映射它EF

Then correctly map it in EF

在你把

@Html.DropDownListFor(
    model => model.CategoryID, category SelectList instance)
)

另一种方法是创建一个自定义模型绑定绑定类别键入

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