序列不包含C＃中的元素錯誤

Question

我正在使用.First()進行API調用並出現sequence contains no elements的錯誤，但使用.FirstOrDefault()時出現同樣的錯誤。該語法應如何更改以避免出現此錯誤？

public class Root 
{ 
    public List<AI> AI { get; set; } 
} 
public class AI 
{ 
    public List<Dictionary<string, string>> AddressInfo { get; set; } 
} 

public class Main[] 
{ 
    var response = syncClient.DownloadString(url); 
    var returnData = JsonConvert.DeserializeObject<Root[]>(response); 
    foreach (Root ro in returnData) 
    { 
     foreach (AI info in ro.AI) 
     { 
      string address = info.AddressInfo.First()["Address1"]); 
      string address2 = info.AddressInfo.First()["Address2"]); 
      string city = info.AddressInfo.First()["City"]); 
      string state = info.AddressInfo.First()["State"]); 
      string zip = info.AddressInfo.First()["Zip"]); 
      Conesole.ReadLine(); 
     } 
    } 
} 

Answer 1

你應該檢查空對象：

foreach (AI info in ro.AI) 
{ 
    var addressInfo = info.AddressInfo.FirstOrDefault(); 

    if(addressInfo != null) 
    { 
     string address = addressInfo["Address1"]; 
     string address2 = addressInfo["Address2"]; 
     string city = addressInfo["City"]; 
     string state = addressInfo["State"]; 
     string zip = addressInfo["Zip"]; 

     Console.ReadLine(); 
    } 
}