具有嵌套名称的扩展名 [英] Extensions with nested names

问题描述

我使用的第三方库有一个名为SessionManager的连接对象。 SessionManager允许您创建不同类型的查询，添加或修改请求。我正在编写一些扩展方法来尝试使编码更快，因为我倾向于在使用此组件时为许多项目重复代码。这是我用来查询cusotmers列表的常规代码：

 SessionManager manager =  new  SessionManager（）; 
 manager.OpenConnection（filename）; 
 IMsgSetRequest MsgRequest = SessionManager.CreateMsgSetRequest（）; 
 ICustomerQuery query = MsgRequest.AppendCustomerQuery（）; 
 query.ActiveStatus.SetValue（ENActiveStatus.All）; 
 IResponse response = SessionManager.DoRequests（MsgRequest）; 
  if （response.StatusCode ==  0 ）{ return （ICustomerRetList）response.Detail; } 
  else  { throw   new 异常（ 查询客户的未知错误： + response.StatusMessage;} 

我不知道是否可以使用扩展，但我希望能够更改我的代码来执行以下操作：

 SessionManager manager =  new  SessionManager（）; 
  return  manager.Customers.QueryAll（）; 

我的想法是，我可以编写一些标准查询，如

 manager.Customers.QueryActive（）; 

和

 manager.Vendors.QueryAll（ ）; 

我无法弄清楚的难点是SessionManager和查询的实际扩展函数之间的部分。看起来你不能做一个带扩展的嵌套类。



我的尝试：



我试过在静态类中创建一个静态类，但是我得到的错误是扩展方法必须在顶级类中。我尝试了以下代码，但编译器似乎并不理解我在尝试的内容：

 public static ICustomerRetList Customer.QueryAll（此SessionManager管理器）

解决方案

您无法创建嵌套扩展方法，但您的扩展方法可以返回其他方法的类/结构实例。 />


尝试这样的事情：

  public   static   class  MyExtensions 
 {
  public   static  CustomerWrapper Customer（此 SessionManager会话）
 {
  return   new  CustomerWrapper（session）; 
} 
} 
 
  public   struct  CustomerWrapper 
 {
  public  CustomerWrapper（SessionManager会话）
 {
 Session = session; 
} 
 
  public  SessionManager Session { get ; } 
 
  public  ICustomerRetList QueryAll（）
 {
 ... 
} 
} 

您只需在客户电话后添加括号：

< pre lang =C＃> SessionManager manager = new SessionManager（）;
return manager.Customer（）。QueryAll（）;

你可以做这样的事情

公共类CustomerManager 
 {
私有SessionManager sessionManager; 
 
 public CustomerManager（SessionManager sessionManager）
 {
 this.sessionManager = sessionManager; 
} 
 
 public ICustomerRetList QueryActive（）
 {
 //使用this.sessionManager查询活跃客户并返回
} 
} 
 
公共静态类MyExtensions 
 {
公共静态CustomerManager客户（此SessionManager sessionManager）
 {
返回新的CustomerManager（sessionManager）; 
} 
} 

然后使用它像

 SessionManager manager = new SessionManager（）; 
 
 manager.Customers（）。QueryActive（）; 

您可以与供应商做同样的事情，所以有一个VendorManager类。

你不能使用复合名称创建扩展方法 - 事实上，你不能使用这样的复合名称创建任何方法。因此，虽然您可以拥有CustomerQueryAll，但您不能拥有Customer.QueryAll。看起来你真正想要的是扩展方法的专业化，所以你会有这样的东西：

  public   static  ICustomerRetList QueryAll（此客户客户）
 {
  //  在这里做点什么。 
} 

那样，你的代码管理器.Customer.QueryAll（ ）因为你现在正在通过客户，所以会有效。

I am using a third party library that has a connection object called a SessionManager. The SessionManager allows you to create different types of requests for querying, adding or modding. I am writing some extension methods to try and make the coding faster as I tend to repeat code for a lot of projects when using this component. Here's the regular code that I would use to query a list of cusotmers:

SessionManager manager = new SessionManager();
manager.OpenConnection(filename);
IMsgSetRequest MsgRequest = SessionManager.CreateMsgSetRequest();
ICustomerQuery query = MsgRequest.AppendCustomerQuery();
query.ActiveStatus.SetValue(ENActiveStatus.All);
IResponse response = SessionManager.DoRequests(MsgRequest);
if(response.StatusCode == 0) { return (ICustomerRetList)response.Detail; }
else { throw new Exception("Unknown error querying customers: " + response.StatusMessage; }

I don't know if it's possible using extensions, but I would like to be able to be able to change my code to do something like this:

SessionManager manager = new SessionManager();
return manager.Customers.QueryAll();

The idea being that I could then code some standard queries like

manager.Customers.QueryActive();

and

manager.Vendors.QueryAll();

The hard part that I am not able to figure out is the part between the SessionManager and the actual extension function for the query. It doesn't seem like you can do a nested class with extensions.

What I have tried:

I've tried creating a static class within a static class, but I get the error that extension methods must be in a top level class. I tried the following code, but the compiler didn't seem to understand what I was trying:

public static ICustomerRetList Customer.QueryAll(this SessionManager manager)

解决方案

You can't created "nested" extension methods, but your extension method can return an instance of a class / struct with other methods on it.

Try something like this:

public static class MyExtensions
{
    public static CustomerWrapper Customer(this SessionManager session)
    {
        return new CustomerWrapper(session);
    }
}

public struct CustomerWrapper
{
    public CustomerWrapper(SessionManager session)
    {
        Session = session;
    }
    
    public SessionManager Session { get; }
    
    public ICustomerRetList QueryAll()
    {
        ...
    }
}

You'll just need to add parentheses after the Customer call:

SessionManager manager = new SessionManager();
return manager.Customer().QueryAll();

You can do something like this

public class CustomerManager
{
    private SessionManager sessionManager;

    public CustomerManager(SessionManager sessionManager)
    {
        this.sessionManager = sessionManager;
    }

    public ICustomerRetList QueryActive()
    {
        // use this.sessionManager to query active customers and return them
    }
}

public static class MyExtensions
{
    public static CustomerManager Customers(this SessionManager sessionManager)
    {
        return new CustomerManager(sessionManager);
    }
}

then use it like

SessionManager manager = new SessionManager();

manager.Customers().QueryActive();

You can do the same thing with Vendors, so have a VendorManager class.

You can't create your extension methods using composite names - in fact, you can't create any method using a composite name like that. So, while you could have CustomerQueryAll, you can't have Customer.QueryAll. What it looks like you really want, is to have a specialization of the extension method so you would have something like this:

public static ICustomerRetList QueryAll(this Customer customer)
{
  // Do something here.
}

That way, your code manager.Customer.QueryAll() would work because you are passing the customer in now.

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