Generic Find（）包含实体框架 [英] Generic Find() with Includes Entity Framework

问题描述

我目前拥有一个完整的通用存储库，但是我缺少一个功能，那就是使用
Include（）和 Find（）一起。

所以现在我有：

  public E FindById< E（int id）其中E：class 
 {
 return DataContext.Set&E;（）。Find（id）; 
} 
  

使用

调用

  var person = PersonRepo.FindById< Person>（personId）; 
  

我想要有类似的东西：

  var person = PersonRepo.FindByIdWithIncludes< Person>（personId，new [] {State.Address}）; 
  

所以，沿着这一行（这只是一个测试）的东西：

  public E FindByIdWithIncludes< E（int id，string [] includes）其中E：class 
 {
 var entitySet = DataContext。设置< E  - 代替;（）; 
 DbQuery< E> entityQuery; 
 
 foreach（var include in includes）
 {
 entityQuery = entitySet.Include（include）; 
} 
 
返回entityQuery.Find（id）; //这是破了
} 
  

可以吗？

解决方案

您不能直接使用查找 查找不适用于包含。您必须使用 SingleOrDefault 。

首先，您需要为实体定义界面以公开其密钥。

  public interface IEntityWithId 
 {
 public int Id {get;组; } 
} 
  

接下来，您可以使用约束编写简单的方法来访问密钥：

  public E FindByIdWithIncludes< E（int id，string [] includes）
其中E：class，IEntityWithId 
 {
 
 IQueryable< E> entityQuery = DataContext.Set< E>（）; 
 
 foreach（var include in includes）
 {
 entityQuery = entityQuery.Include（include）; 
} 
 
返回entityQuery.SingleOrDefault（e => e.Id == id）; 
} 
  

Btw。您可以使用强类型的包含 - 这里是一个例子。

I currently have a complete generic repository but I'm missing one feature and that is to use Include() and Find() together.

So now I have:

public E FindById<E>(int id) where E : class
{
    return DataContext.Set<E>().Find(id);
}

called using

var person = PersonRepo.FindById<Person>(personId);

I would like to have something similar to:

var person = PersonRepo.FindByIdWithIncludes<Person>(personId,new[]{"State.Address"});

So, something along this lines (this is only a test):

public E FindByIdWithIncludes<E>(int id, string[] includes) where E : class
{
    var entitySet = DataContext.Set<E>();
    DbQuery<E> entityQuery;

    foreach (var include in includes)
    {
        entityQuery = entitySet.Include(include);
    }

    return entityQuery.Find(id); //this is were it breaks
}

Is it possible?

解决方案

You cannot use Find directly - Find doesn't work with includes. You must use SingleOrDefault.

First you need to define interface for your entities to expose their key.

public interface IEntityWithId 
{
    public int Id { get; set; }
}

Next you can write simple method with constrain to get access to the key:

public E FindByIdWithIncludes<E>(int id, string[] includes) 
    where E : class, IEntityWithId
{          

    IQueryable<E> entityQuery = DataContext.Set<E>();

    foreach (var include in includes)
    {
            entityQuery = entityQuery.Include(include);
    }

    return entityQuery.SingleOrDefault(e => e.Id == id); 
}

Btw. you can use strongly typed includes - here is an example.

这篇关于Generic Find（）包含实体框架的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！