代码之家 › 专栏 › 技术社区 › Glory Raj

添加范围不适用于列表[重复]

c#-4.0 linq list .net c#

-2

Glory Raj · 技术社区 · 7 年前

public class PayeeContactDetails
{

    //[JsonProperty("id")]
    //[DefaultValue("")]
    //public int ID { get; set; }

    [JsonProperty("contact_name")]
    [DefaultValue("")]
    public string ContactName { get; set; }

    [JsonProperty("contact_email")]
    [DefaultValue("")]
    public string ContactEmail { get; set; }
    ........
    ........
}

 public class PayeeContactGroup
 {   
    [JsonProperty("payee_contacts")]    
    public List<PayeeContactDetails> PayeeContact { get; set; }

 }

在这里,我从api响应中获取数据,在完成所有页面后,我需要一次将所有数据发送到DB

 PayeeContactGroup payeeContactDetails = new PayeeContactGroup();

  var response = httpClient.GetAsync(uri).Result;
  if (response.IsSuccessStatusCode)
  {
     string data = response.Content.ReadAsStringAsync().Result;
     var payeeContactGroupDetails = JsonConvert.DeserializeObject<PayeeContactGroup>(data);

     if(payeeContactGroupDetails.PayeeContact != null && payeeContactGroupDetails.currentPage == 1)
      {
         payeeContactDetails.PayeeContact = payeeContactGroupDetails.PayeeContact.ToList();
      }
      else if(payeeContactGroupDetails.PayeeContact != null && payeeContactGroupDetails.currentPage > 1)
      { 
         payeeContactDetails.PayeeContact.AddRange(payeeContactGroupDetails.PayeeContact); // error at this line 
      }
      .......
      ......
  }

但我在这条线

“payeeContactDetails.PayeeContact.AddRange(payeeContactGroupDetails.PayeeContact);” 错误:“对象引用未设置为对象”

非常感谢

2 回复 | 直到 7 年前

Romano Zumbé 7 年前

您需要创建 List

public class PayeeContactGroup
 {   
    [JsonProperty("payee_contacts")]    
    public List<PayeeContactDetails> PayeeContact { get; set; } = new List<PayeeContactDetails>();

 }

列表 只有在必要时:

PayeeContactGroup payeeContactDetails = new PayeeContactGroup();

var response = httpClient.GetAsync(uri).Result;
if (response.IsSuccessStatusCode)
{
   string data = response.Content.ReadAsStringAsync().Result;
   var payeeContactGroupDetails = JsonConvert.DeserializeObject<PayeeContactGroup>(data);

   if(payeeContactGroupDetails.PayeeContact != null && payeeContactGroupDetails.currentPage == 1)
    {
       payeeContactDetails.PayeeContact = payeeContactGroupDetails.PayeeContact.ToList();
    }
    else if(payeeContactGroupDetails.PayeeContact != null && payeeContactGroupDetails.currentPage > 1)
    { 
         if(payeeContactDetails.PayeeContact == null)
         {
              payeeContactDetails.PayeeContact = new List<PayeeContactDetails>();
         }
         payeeContactDetails.PayeeContact.AddRange(payeeContactGroupDetails.PayeeContact); // error at this line 
    }
      .......
      ......
}

DavidG 7 年前

AddRange 方法正在尝试添加到null。这可以通过代码实现:

PayeeContactGroup payeeContactDetails = new PayeeContactGroup();

payeeContactDetails.PayeeContact = new List<PayeeContactDetails>();