将值分配到列表< object>在模型类中 [英] Assinging values into a list<object> in a model class

问题描述

public class Parameter
{
  public int Id {get;set;}
  public string name {get;set;}
  public List<Phonenumber> Phonenumbers{get;set}
}

public class Phonenumber
{
  public string number1 {get;set;}
  public string number2 {get;set;}
  public string number3 {get;set;}
}

public ActionResult SmeDirPage(Phonenumber number)
   {
      Parameter para = new Parameter ();

      // How do i assign value to para.Phonenumbers.number1
   }

我尝试过：



请问如何将值传递到此列表

What I have tried:

Please how can i pass values to this list

public ActionResult SmeDirPage(Phonenumber number)
   {
      Parameter para = new Parameter ();
      foreach(var item in para.Phonenumbers) // Error **Object reference not set to an instance of an object**
      {
        item.number1 = number.number1;
        item.number2 = number.number2;
        item.number3 = number.number3;
      }
   }

推荐答案

你已经将Phonenumbers定义为List但是没有你是在创建列表所以para.Phonenumbers总是为null。您可以在构造函数中创建一个新List。

You've define Phonenumbers to be a List but at no point are you creating the list so para.Phonenumbers is always going to be null. You can create a new List in the constructor.

public class Parameter
{
  public int Id {get;set;}
  public string name {get;set;}
  public List<Phonenumber> Phonenumbers{get;set}
  
  public Parameter()
  {
     this.Phonenumbers = new List<Phonenumber>();
  }
}

你的代码没有意义，因为你的 Phonenumbers 类型列表< Phonenumber> 的属性将始终为空值，因此它永远不会进入 foreach-loop 即使您初始化列表。

Your code doesn't make sense because your Phonenumbers property of type List<Phonenumber> will always have an empty value, thus it will never go inside your foreach-loop even if you initialize your List.

Quote：

请问如何将值传递给此列表

Please how can i pass values to this list

您不需要循环为您的值分配值列表因为它已经预期某种类型 Phonenumber 。你需要做的就是这样：

You don't need a loop to assign values to your List because it's already expecting a type of Phonenumber. What you need to do is simply just like this:

var phoneNumbers = new List<Phonenumber>();
phoneNumbers.Add(numbers);

然后您可以将 phoneNumbers 值分配给您的参数这样的对象：

You can then assign the phoneNumbers value to your Parameter object like this:

Parameter para = new Parameter();
para.Id = 1;
para.name = "Vynn Markus";
para.Phonenumbers = phoneNumbers;

完全放入它们，你的整个 ActionResult 方法现在看起来像这样：

To put them altogether, your whole ActionResult method would now look something like this:

public ActionResult SmeDirPage(Phonenumber numbers)
{
    var phoneNumbers = new List<Phonenumber>();
	phoneNumbers.Add(numbers);
		
	Parameter para = new Parameter();
	para.Id = 1;
	para.name = "Vynn Markus";
	para.Phonenumbers = phoneNumbers;
}

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