如何将此代码转换为服务模式? [英] How to convert this code to service pattern?

问题描述

这是我的代码:

        [HttpGet]
    public ActionResult GetCategor(int catId)
    {
      using (uuEntities ems = new uuEntities())
      {
        return Json(ems.SupportSubCats.Where(x => x.CatID == catId).Select(
        x => new
        {
          SubId = x.SubCatID,
          SUbName = x.SubCatName
        }).ToList(), JsonRequestBehavior.AllowGet);
      }
    }

我尝试过的:

在控制器中:

   [HttpGet]
    public ActionResult GetCategor(int catId)
    {
        return Json(_service.List(int catId), JsonRequestBehavior.AllowGet);
      }
    } 

服务中:

    public void List(int catId)
    {
      return new GenericRepository<SupportSubCategory>(_factory.ContextFactory)
        .Get(filter: (x => x.CatID == catId))
        .Select(x => new
        {
          SubId = x.SubCatID,
          SUbName = x.SubCatName
        }).ToList();
    }

我认为我的退货类型不正确，请提出解决方案.接近公共void时，我收到一个错误，表明void无法返回列表.

I think my return type is incorrect please suggest me the solution. Near public void, i am getting an error that void can not return the list.

推荐答案

void方法不会向其调用方返回任何值. 您只能在void方法中使用空的return来退出该方法-但不能返回任何值.

A void methods does not return any value to it's caller. You can use an empty return in a void method only to exit the method - but you can't return any value.

此代码是完全有效的，并已广泛用作惯例:

This code is perfectly valid and widely used as a common practice:

public void DoSomething()
{
    if(<someCondition>)
    {
        return;
    }
    // The rest of the code will only be executed if <someCondition> evalualtes to false
}

通常，在将参数传递到方法中时需要使用此模式，并且需要在实际执行方法的其余部分之前对其进行验证.

Usually, you use this pattern when you are passing parameters into the method and need to validate them before actually performing the rest of the method.

但是，此代码无效，并且将无法编译:

This code, however, is not valid and will not compile:

public void DoSomething()
{
    if(<someCondition>)
    {
        return false; // Here is your compiler error...
    }
    // The rest of the code will only be executed if <someCondition> evalualtes to false
}

在评论中我们进行对话之后，您可能应该创建一个类来保存Select的结果，而不要使用匿名类型，并从您的方法中返回该类的列表:

Following our conversation in the comments, you should probably create a class to hold the results of the Select instead of using an anonymous type, and return a list of that class from your method:

// Note: I've renamed your method to something a little bit more meaningful
public List<SubDetails> ListSubDetails(int catId) 
{
  return new GenericRepository<SupportSubCategory>(_factory.ContextFactory)
    .Get(filter: (x => x.CatID == catId))
    .Select(x => new SubDetails()
    {
      SubId = x.SubCatID,
      SUbName = x.SubCatName
    }).ToList();
}

...

public class SubDetails
{
    public Int SubId {get; set;} // I'm guessing int here...
    public string SUbName {get; set;} // I'm guessing string here...
 }

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