使用数据库优先方法时覆盖或替换默认构造函数 [英] Override or replace default constructor when using database first approach

问题描述

我们正在使用数据库优先方法来创建我们的MVC模型，这意味着框架会在主.cs文件中自动生成默认构造函数.但是，我有几个默认值要设置，问题是每次.edmx更新时，此框架都会为此模型生成一个基本的.cs文件.有没有办法在部分类之类的方法中重写此构造函数?

We are using the database first approach to creating our MVC models, which means the framework auto-generates a default constructor in the primary .cs file. I have a couple default values that I'd like to set, however, and the problem is this framework generates a basic .cs file for this model each time the .edmx is updated. Is there any way to either override this constructor in something like a partial class?

示例

public partial class Product
{
    // The framework will create this constructor any time a change to 
    // the edmx file is made. This means any "custom" statements will 
    // be overridden and have to be re-entered
    public Product()
    {
        this.PageToProduct = new HashSet<PageToProduct>();
        this.ProductRates = new HashSet<ProductRates>();
        this.ProductToRider = new HashSet<ProductToRider>();
    }
}

推荐答案

您可以编辑生成类的t4模板，以使其生成在无参数构造函数中调用的局部方法.然后，您可以在随附的局部类中实现此方法.

You could edit the t4 template that generates the classes to make it generate a partial method that is called in the parameterless constructor. Then you can implement this method in an accompanying partial class.

编辑后，您生成的代码应如下所示:

After editing, your generated code should look like this:

public Product()
{
    this.PageToProduct = new HashSet<PageToProduct>();
    this.ProductRates = new HashSet<ProductRates>();
    this.ProductToRider = new HashSet<ProductToRider>();
    Initialize();
}

partial void Initialize();

现在在您自己的局部课程中:

Now in your own partial class:

partial class Product
{
    partial void Initialize()
    {
        this.Unit = 1; // or whatever.
    }
}

完全覆盖默认构造函数的好处是，您可以保留EF的初始化代码.

The advantage over completely overriding the default constructor is that you keep EF's initialization code.

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