如何在NewtonJson中检查API /empty错误并在C#中显示DataSet
如何在NewtonJson中检查API /empty错误并在C#中显示DataSet
提问于 2019-12-26 09:44:47
我正在尝试显示数组或值的简单元素，下面是我的JSON字符串(来自python pandas的API )
{
"msg": "success",
"state": 10000,
"data": {
"data": [
{
"index": 0,
"test_1": 110,
"test_2": "000001",
"test_3": "CN",
"test_4": "Bank",
"test_5": 893,
"test_6": 229
}
],
"schema": {
"fields": [
{
"type": "integer",
"name": "index"
},
{
"type": "string",
"name": "test_1"
},
{
"type": "string",
"name": "test_2"
},
{
"type": "number",
"name": "test_3"
},
{
"type": "number",
"name": "test_4"
},
{
"type": "number",
"name": "test_5"
},
{
"type": "string",
"name": "test_6"
}
],
"pandas_version": "0.20.0",
"primaryKey": [
"index"
]
}
}
}下面的C#代码是我正在使用的查询TestDataset.cs
using System;
using System.IO;
using System.Net;
using Newtonsoft.Json.Linq;
using ExcelDna.Integration;
using Excel = Microsoft.Office.Interop.Excel;
namespace Test_Atune
{
public class Request
{
Excel.Application ExcelApp = (Excel.Application)ExcelDnaUtil.Application;
public object GetDatasetFromUrl(string root, string path, string headval, Excel.Range excelAddress)
{
string historicalData= "{}";
var webConnection = new WebClient();
webConnection.Headers.Add("Host", headval);
try
{
historicalData = webConnection.DownloadString(root+path);
}
catch (WebException ex)
{
string error_str = ex.Message;
if (ex.Status.ToString() == "ConnectFailure" || ex.Status.ToString() == "Timeout")
{
root = Constant.setURL_ROOT_COMMON(root);
try
{
historicalData= webConnection.DownloadString(root + path);
}
catch (WebException ex2)
{
return "";
}
}
}
finally
{
webConnection.Dispose();
}
JObject jsonFeed = JObject.Parse(historicalData);
Excel.Range range = excelAddress;
JObject B = new JObject();
JArray data = (JArray)jsonFeed["data"]["data"];
JArray columns = (JArray)jsonFeed["data"]["schema"]["fields"];
int rowNum = data.Count;
int colNum = columns.Count;
Excel.Range range_head = ExcelApp.Cells[range.Row + 1, range.Column];
range_head = range_head.get_Resize(1, colNum);
Excel.Range range_data = ExcelApp.Cells[range.Row + 2, range.Column];
range_data = range_data.get_Resize(rowNum, colNum);
// write header
object[,] headerData = new object[1, colNum];
for (int iCol = 0; iCol < colNum; iCol++)
{
headerData[0, iCol] = columns[iCol]["name"];
}
range_head.Value2 = headerData;
// write data
object[,] cellData = new object[rowNum, colNum];
int iRow = 0;
foreach (JObject jo in data)
{
var a = jo["test_code"];
for (int iCol = 0; iCol < colNum; iCol++)
{
if (columns[iCol]["test_1"].ToString() == "string")
{
cellData[iRow, iCol] = "'" + jo[columns[iCol]["name"].ToString()];
}
else
{
cellData[iRow, iCol] = jo[columns[iCol]["name"].ToString()];
}
}
iRow += 1;
}
range_data.Value2 = cellData;
return "Total" + rowNum.ToString() + "cells";
}
}
}下面是request.cs的代码
using ExcelDna.Integration;
using Excel = Microsoft.Office.Interop.Excel;
namespace Test_Atune
{
public class Dataset
{
public static string baseurl = Constant.URL_ROOT_COMMON;
public static string headval = Constant.HEADVAL_COMMON;
public static Request request = new Request();
[ExcelFunction(Category = "test", IsMacroType = true, Description = "test dataset")]
public static object TEST_DATASET(
[ExcelArgument(Description = "test_code")] string test_1,
[ExcelArgument(Description = "YYYYMMDD")] string test_2,
[ExcelArgument(Description = "YYYYMMDD")] string test_3
)
{
string parstr = @"/test_dataset/?" +
@"test_1=" + test_1 +
@"&test_2=" + test_2 +
@"&test_3=" + test_3;
ExcelReference caller = (ExcelReference)XlCall.Excel(XlCall.xlfCaller);
Excel.Range rg = caller.ToPiaRange();
return ExcelAsyncUtil.Run("TEST_DATASET",
new object[] { parstr },
() => request.GetDatasetFromUrl(Constant.URL_ROOT_COMMON, parstr, headval, rg));
}
}
}我在JArray columns = (JArray)jsonFeed["data"]["schema"]["fields"];上得到了下面的错误
System.NullReferenceException HResult=0x80004003 message=Object reference not set to an instance of an object.我试着调试得到了下面的结果，Name: historicalData, Value:"{}"; Name: jsonFeed,Vaule:Null; Name:B,Vaule:{{}}, Name:data, Value:"null"
我是C#的新手，这是一个数组，域，url问题，还是其他的问题？我该怎么做呢？非常感谢你的建议。
回答 1
Stack Overflow用户
发布于 2019-12-26 09:56:44
错误:未将对象引用设置为对象的实例。这意味着["data"]、["data"]["schema"]或["data"]["schema"]["fields"]下的一个或所有数据不存在。
我刚刚测试了您的代码，基于给定的json，下面的代码工作得很好。
JArray columns = (JArray)jsonFeed["data"]["schema"]["fields"];
建议：使用调试器，看看jsonFeed的值是否正确，因为这是我唯一不能重现的东西。如果无法使用调试器，请在已分析的对象上使用.ToString()来记录已分析的对象。(jsonFeed.ToString())
注意：你的json有一个问题。建议"test_3": CN,为CN上带引号的"test_3": "CN",。
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/59483101
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