我正在通过SSIS脚本组件获取Web API JSON响应，它以下列格式返回：
{
"Success": true,
"Response": {
"Applications": [
{
"App_ID": 1638486,
"App_Ref": "Test Example",
"Status": "Complete",
"Error_Code": null,
"Error_Message": null,
"Create_Dt": "2014-05-14 03:09:01.030 +00:00",
"Modify_Dt": "2014-05-14 03:10:59.757 +00:00",
"Client_Name": "Silver Chef",
"Client_Code": "SLVC01",
"Centrelink_Status": "Receiving_Logons"
},
{
"App_ID": 1637906,
"App_Ref": "SME Demo",
"Status": "Complete",
"Error_Code": null,
"Error_Message": null,
"Create_Dt": "2015-10-08 03:07:26.793 +00:00",
"Modify_Dt": "2015-10-08 03:23:32.833 +00:00",
"Client_Name": "Silver Chef",
"Client_Code": "SLVC01",
"Centrelink_Status": "Receiving_Logons"
},
{
"App_ID": 1585286,
"App_Ref": "Test",
"Status": "Receiving_Logons",
"Error_Code": null,
"Error_Message": null,
"Create_Dt": "2015-12-04 03:12:49.617 +00:00",
"Modify_Dt": "2015-12-04 03:12:49.617 +00:00",
"Client_Name": "Silver Chef",
"Client_Code": "SLVC01",
"Centrelink_Status": "Receiving_Logons"
}
],
"Current_Dt": "2016-11-11 01:01:01.743 +00:00",
"Last_App_Dt": "2016-10-03 22:48:56.397 +00:00",
"Count": 500,
"Total": 1870
}
}
我已宣布以下课程：
public class Application
{
public int App_ID { get; set; }
public string App_Ref { get; set; }
public string Status { get; set; }
public int Error_Code { get; set; }
public string Error_Message { get; set; }
public DateTime Create_Dt { get; set; }
public DateTime Modify_Dt { get; set; }
public string Client_Name { get; set; }
public string Client_Code { get; set; }
public int Centrelink_Status { get; set; }
}
public class Response
{
public List<Application> Applications { get; set; }
public string Current_Dt { get; set; }
public string Last_App_Dt { get; set; }
public int Count { get; set; }
public int Total { get; set; }
}
public class RootObject
{
public bool Success { get; set; }
public Response Response { get; set; }
}
And this is the method that I am using to get the response.
private RootObject GetWebServiceResult(string vAPIUrl)
{
string vAPIToken = Variables.APIToken;
//Create Web Request
HttpWebRequest apireq = (HttpWebRequest)WebRequest.Create(vAPIUrl);
apireq.ContentType = "application/json";
apireq.Method = "POST";
string jsonPostStr = "{\"Settings\": {\"API_Token\": \"" + vAPIToken + "\"}, \"Payload\": {}}";
byte[] postString = Encoding.UTF8.GetBytes(jsonPostStr);
apireq.ContentLength = postString.Length;
Stream jsonStream = apireq.GetRequestStream();
jsonStream.Write(postString, 0, postString.Length);
jsonStream.Close();
// Get Web Response
HttpWebResponse apirsp = (HttpWebResponse)apireq.GetResponse();
RootObject jsonResponse = null;
Stream jsonRspStream = apirsp.GetResponseStream();
string apiResponseString = null;
using (StreamReader reader = new StreamReader(jsonRspStream))
{
apiResponseString = reader.ReadToEnd();
Console.WriteLine(apiResponseString);
reader.Close();
}
JavaScriptSerializer returnJson = new JavaScriptSerializer();
//var serialJsonStr = returnJson.Serialize(apiResponseString);
System.Windows.Forms.MessageBox.Show(apiResponseString);
jsonResponse = returnJson.Deserialize<RootObject>(apiResponseString);
return jsonResponse;
}
我的问题是 returnJson.Deserialize（apiResponseString）; 似乎返回null并随后使其失败。
我缺少什么？我认为在这个阶段我的代码是盲目的。
提前致谢
答案 0 :(得分：3)
Application类有几个问题：
您已将Application.Error_Code定义为整数：
public int Error_Code { get; set; }
但实际上，在JSON中，它有一个空值：
"Error_Code": null,
因此Error_Code需要是引用类型（string）或可空值类型（int?），具体取决于非空时它所拥有的内容。
您已将Centrelink_Status定义为int，但在JSON中，它是一个字符串：
"Centrelink_Status": "Receiving_Logons"
因此它也需要是数据模型中的字符串。
因此，您的Application课程应如下所示：
public class Application
{
public int App_ID { get; set; }
public string App_Ref { get; set; }
public string Status { get; set; }
public int? Error_Code { get; set; } // Or string, if not numeric
public string Error_Message { get; set; }
public DateTime Create_Dt { get; set; }
public DateTime Modify_Dt { get; set; }
public string Client_Name { get; set; }
public string Client_Code { get; set; }
public string Centrelink_Status { get; set; }
}
如果JSON中有DateTime值的可能性，您可能还希望这些null属性可以为空。
顺便说一下，当我尝试反序列化这个JSON时，我抛出了异常，而不是返回null值：
System.InvalidOperationException was unhandled
Message="Cannot convert null to a value type."
Source="System.Web.Extensions"
StackTrace:
在您的实际代码中，您是否正在捕捉并吞咽异常？这不是一个坏主意，因为它往往会隐藏诸如此类的错误。至少，在调试时，每当抛出任何异常（包括第一次机会异常）时都应该中断 - 即使这是不的默认行为。见Managing Exceptions with the Debugger。如果发现某些类型的异常经常被抛出并且与调试无关，则可以有选择地重新忽略它们。如果你这样做了，那么这个bug就更容易追踪了。不可否认，错误不是很明确，但确实给出了一个暗示。如果您使用json.net反序列化您的JSON，错误消息将更加清晰：
Newtonsoft.Json.JsonSerializationException occurred
Message="Error converting value {null} to type 'System.Int32'. Path 'Response.Applications[0].Error_Code', line 9, position 26."
Source="Newtonsoft.Json"
StackTrace:
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.EnsureType(JsonReader reader, Object value, CultureInfo culture, JsonContract contract, Type targetType) in C:\Development\Releases\Json\Working\Newtonsoft.Json\Working-Signed\Src\Newtonsoft.Json\Serialization\JsonSerializerInternalReader.cs:line 986
InnerException: System.InvalidCastException
Message="Null object cannot be converted to a value type."
Source="mscorlib"
StackTrace:
at System.Convert.ChangeType(Object value, Type conversionType, IFormatProvider provider)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.EnsureType(JsonReader reader, Object value, CultureInfo culture, JsonContract contract, Type targetType) in C:\Development\Releases\Json\Working\Newtonsoft.Json\Working-Signed\Src\Newtonsoft.Json\Serialization\JsonSerializerInternalReader.cs:line 979
InnerException: