ASP.NET Core只返回一个实体中集合的第一个值 [英] ASP.NET Core only returning first value of a collection in an entity

问题描述

我有一个MyEntity类，其中包含一个集合：

I have a class MyEntity with a collection within it:

public class MyEntity
{    
    [Key]
    public int MyId { get; set; }
    [Display(Name = "Process Name")]
    public string ProcessName { get; set; }
    public ICollection<Step> ProcessSteps { get; set; }
}

与课程一个很多的关系Step：

A one-many relationship with class Step:

public class Step
{
    ...
    [ForeignKey("MyEntityForeignKey")]
    public MyEntity { get; set; }
}

以下是返回指定MyEntity的API调用：

Below is the API call to return a specified MyEntity:

public async Task<IActionResult> MyEntity(int? id)
{
    if (id == null)
    {
        return Ok(await _context.MyEntity.ToListAsync());
    }

    var process = _context.MyEntity.Where(f => f.MyId == id).Include(g => g.ProcessSteps);

    if (process.Count() == 0)
    {
        return NotFound();
    }

    return Ok(process.First());
}

运行这个时，一切看起来都很棒，除了集合。调试时，显示正确的值。即使我在这些集合中有2+项目，当它返回响应 Ok 时，它总是返回ProcessSteps集合中的第一个项目。

When running this, everything looks great except for the collection. While debugging, the correct values are shown. Even though I have 2+ items in these collections, it always returns just the first item in the ProcessSteps collection from MyClass when it returns the response Ok.

编辑：

看起来像我的外键返回的回应是罪魁祸首。迭代和归零外键似乎有固定的东西。

It looks like returning the response with my foreign key attached was the culprit. Iterating through and nulling the foreign key seems to have fixed things.

foreach (Step step in MyEntity.ProcessSteps)
{
     Step.MyEntity = null;
}

return Ok(MyEntity.ProcessSteps)

推荐答案

我有一个类似的问题，只有目标集合的第一个实体被返回，除非我设置为null，否则所有的内部引用。
但是我能够通过映射我的模型到dto对象（或ViewModel）返回之前。 dto通常是模型实体的一个子集。这样我就不用设置内部引用的空白了。


一般来说，我认为这是一个很好的做法，只需要把客户端只返回到严格需要的属性，而不给出整个模型对象。

I had a similar issue, where only the first entity of the target collection was returned unless I was setting to null all the inner references.
However I was able to solve this by mapping my model to dto object (or ViewModel) before returning it. The dto has usually a subset of the model entity. In this way I did not have to set to null the inner references.

In general I think it is a good practice to return to the client only the properties that are strictly needed, without giving the whole model object.

这篇关于ASP.NET Core只返回一个实体中集合的第一个值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！