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如何使用 System.Text.Json 支持某种无效的 JSON
本文将介绍如何能够在 JSON 中使用注释、尾随逗号和带引号的数字,以及如何将数字编写为字符串。
默认情况下,JSON 中不允许使用注释和尾随逗号。 若要在 JSON 中允许注释,请将 JsonSerializerOptions.ReadCommentHandling 属性设置为 JsonCommentHandling.Skip
。
若要允许尾随逗号,请将 JsonSerializerOptions.AllowTrailingCommas 属性设置为 true
。 下面的示例演示如何允许这两者:
C#
var options = new JsonSerializerOptions
{
ReadCommentHandling = JsonCommentHandling.Skip,
AllowTrailingCommas = true,
};
WeatherForecast weatherForecast = JsonSerializer.Deserialize<WeatherForecast>(
jsonString,
options
)!;
Dim options As JsonSerializerOptions = New JsonSerializerOptions With {
.ReadCommentHandling = JsonCommentHandling.Skip,
.AllowTrailingCommas = True
}
Dim weatherForecast1 = JsonSerializer.Deserialize(Of WeatherForecast)(jsonString, options)
下面是包含注释和尾随逗号的示例 JSON:
JSON
{
"Date": "2019-08-01T00:00:00-07:00",
"TemperatureCelsius": 25, // Fahrenheit 77
"Summary": "Hot", /* Zharko */
// Comments on
/* separate lines */
}
某些序列化程序将数字编码为 JSON 字符串(括在引号中)。
例如:
JSON
{
"DegreesCelsius": "23"
}
不是:
JSON
{
"DegreesCelsius": 23
}
若要在整个输入对象图中序列化带引号的数字或接受带引号的数字,请设置 JsonSerializerOptions.NumberHandling,如以下示例中所示:
C#
using System.Text.Json;
using System.Text.Json.Serialization;
namespace QuotedNumbers
{
public class Forecast
{
public DateTime Date { get; init; }
public int TemperatureC { get; set; }
public string? Summary { get; set; }
};
public class Program
{
public static void Main()
{
Forecast forecast = new()
{
Date = DateTime.Now,
TemperatureC = 40,
Summary = "Hot"
};
JsonSerializerOptions options = new()
{
NumberHandling =
JsonNumberHandling.AllowReadingFromString |
JsonNumberHandling.WriteAsString,
WriteIndented = true
};
string forecastJson =
JsonSerializer.Serialize<Forecast>(forecast, options);
Console.WriteLine($"Output JSON:\n{forecastJson}");
Forecast forecastDeserialized =
JsonSerializer.Deserialize<Forecast>(forecastJson, options)!;
Console.WriteLine($"Date: {forecastDeserialized.Date}");
Console.WriteLine($"TemperatureC: {forecastDeserialized.TemperatureC}");
Console.WriteLine($"Summary: {forecastDeserialized.Summary}");
}
}
}
// Produces output like the following example:
//
//Output JSON:
//{
// "Date": "2020-10-23T12:27:06.4017385-07:00",
// "TemperatureC": "40",
// "Summary": "Hot"
//}
//Date: 10/23/2020 12:27:06 PM
//TemperatureC: 40
//Summary: Hot
Imports System.Text.Json
Imports System.Text.Json.Serialization
Namespace QuotedNumbers
Public Class Forecast
Public Property [Date] As Date
Public Property TemperatureC As Integer
Public Property Summary As String
End Class
Public NotInheritable Class Program
Public Shared Sub Main()
Dim forecast1 As New Forecast() With {
.[Date] = Date.Now,
.TemperatureC = 40,
.Summary = "Hot"
}
Dim options As New JsonSerializerOptions() With {
.NumberHandling = JsonNumberHandling.AllowReadingFromString Or
JsonNumberHandling.WriteAsString,
.WriteIndented = True
}
Dim forecastJson As String = JsonSerializer.Serialize(forecast1, options)
Console.WriteLine($"Output JSON:{forecastJson}")
Dim forecastDeserialized As Forecast = JsonSerializer.Deserialize(Of Forecast)(forecastJson, options)
Console.WriteLine($"Date: {forecastDeserialized.[Date]}")
Console.WriteLine($"TemperatureC: {forecastDeserialized.TemperatureC}")
Console.WriteLine($"Summary: {forecastDeserialized.Summary}")
End Sub
End Class
End Namespace
' Produces output like the following example:
'
'Output JSON:
'{
' "Date": "2020-10-23T12:27:06.4017385-07:00",
' "TemperatureC": "40",
' "Summary": "Hot"
'}
'Date: 10/23/2020 12:27:06 PM
'TemperatureC: 40
'Summary: Hot
在通过 ASP.NET Core 间接使用 System.Text.Json
时,反序列化时允许使用带引号的数字,因为 ASP.NET Core 指定 Web 默认选项。
若要允许或写入特定属性、字段或类型的带引号的数字,请使用 [JsonNumberHandling] 特性。