处理Newtonsoft.Json中的十进制值 [英] Handling decimal values in Newtonsoft.Json
问题描述
编辑：已经差不多5年了，我认为这不是一条路。客户端应以正确的数字格式发布数据。使用当前的框架，如React或Angular，或具有适当的架构和错误处理&验证，我认为这几乎不是问题。
It's been almost 5 years and I don't think this is the way to go. The client should post the data in the correct numerical format. With current frameworks like React or Angular, or with a proper architecture and error handling & validation, i think this is almost a non-problem.
但是如果有人想要展示他们的Json.NET肌肉，请随时查看答案。
But if anyone wishes to flex their Json.NET muscles, feel free to check the answers.
我有一个MVC应用程序，我在其中处理一些JSON。这很简单。我在ModelBinder中有这么简单的代码：
I have a MVC application and I handle some JSON in it. That's simple. I have this simple piece of code in my ModelBinder:
return JsonConvert.DeserializeObject(jsonString, bindingContext.ModelType, new JsonSerializerSettings
{
NullValueHandling = NullValueHandling.Ignore,
MissingMemberHandling = MissingMemberHandling.Ignore,
Formatting = Formatting.None,
DateFormatHandling = DateFormatHandling.IsoDateFormat,
FloatParseHandling = FloatParseHandling.Decimal
});
它完美无瑕。
嗯，等等。
假设我有这个课程：
public class MyClass
{
public decimal MyProp { get; set; }
}
如果我尝试反序列化这个json：
If I try to deserialize this json:
"{\"MyProp\": 9888.77}"
当然可行，因为 9888.77 是一个Javascript浮点值。我想。
Of course it works, since 9888.77 is a Javascript float value. I think.
但是我的页面中有一个蒙面输入，让JSON看起来像这样（对不起我的英文）：
But I have a masked input for money in my page that makes the JSON look like this (sorry about my english):
"{\"MyProp\": \"9.888,77\" }"
AAAND，它失败了。它说它无法将字符串转换为十进制。
AAAND, it fails. It says that it Could not convert string to decimal.
好的，这是公平的。它不是JS浮点数，但是 Convert.ToDecimal（9.888,77）以我想要的方式工作。
Ok, that's fair. It is not a JS float, but Convert.ToDecimal("9.888,77") works the way I want.
我在互联网上阅读了一些关于自定义反序列化器的教程，但是我可以为我的应用程序中的每个类定义一个自定义反序列化器。
I've read some tutorials on the internet about custom deserializers, but its inviable for me to define a custom deserializer for every single class I have in my application.
我想要的是简单地重新定义JSON.Net将字符串转换为十进制属性的方式，在任何我想要反序列化的类中。当当前转换器不起作用时，我想在转换小数的过程中注入 Convert.ToDecimal 函数。
What I want is to simple redefine the way JSON.Net converts a string to a decimal property, in any class i'll ever want to deserialize to. I want to inject the Convert.ToDecimal function in the process of converting decimals, when the current converter doesn't work.
有没有办法可以做到？
我认为有办法做到这一点，所以我改变了我的代码。
I thought there was a way to do it, so I changed my code a little bit.
JsonSerializer serializer = new JsonSerializer
{
NullValueHandling = NullValueHandling.Ignore,
MissingMemberHandling = MissingMemberHandling.Ignore,
Formatting = Formatting.None,
DateFormatHandling = DateFormatHandling.IsoDateFormat,
FloatParseHandling = FloatParseHandling.Decimal,
};
return serializer.Deserialize(new DecimalReader(jsonStr), bindingContext.ModelType);
创建此类：
public class DecimalReader : JsonTextReader
{
public DecimalReader(string s)
: base(new StringReader(s))
{
}
public override decimal? ReadAsDecimal()
{
try
{
return base.ReadAsDecimal();
}
catch (Exception)
{
if (this.TokenType == JsonToken.String)
{
decimal value = 0;
bool convertible = Decimal.TryParse(this.Value.ToString(), out value);
if (convertible)
{
return new Nullable<decimal>(value);
}
else { throw; }
}
else
{
throw;
}
}
}
}
但是它非常难看：它只在崩溃时执行我想要的，并依赖于 base.ReadAsDecimal（）崩溃。它不可能更难看。
But it is very ugly: it executes what I want only when it crashes, and depends on base.ReadAsDecimal() crashing. It couldn't be more ugly.
并且不起作用：将值1.231,23转换为类型'System.Nullable1 [系统时出错.Decimal]。路径'MyProp'，第X行，第Y位。
价值本身正在被转换，但也许由于某种原因它仍然试图放字符串1.231,23为小数。
The value itself is being converted, but perhaps for some reason it still tries to put the string "1.231,23" into a decimal.
那么，有没有办法正确地做到这一点？
So, is there a way to do it properly?
推荐答案
您可以使用自定义 JsonConverter 类来处理这两种格式（JSON编号表示和屏蔽字符串格式）。
You can handle both formats (the JSON number representation and the masked string format) using a custom JsonConverter class like this.
class DecimalConverter : JsonConverter
{
public override bool CanConvert(Type objectType)
{
return (objectType == typeof(decimal) || objectType == typeof(decimal?));
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
JToken token = JToken.Load(reader);
if (token.Type == JTokenType.Float || token.Type == JTokenType.Integer)
{
return token.ToObject<decimal>();
}
if (token.Type == JTokenType.String)
{
// customize this to suit your needs
return Decimal.Parse(token.ToString(),
System.Globalization.CultureInfo.GetCultureInfo("es-ES"));
}
if (token.Type == JTokenType.Null && objectType == typeof(decimal?))
{
return null;
}
throw new JsonSerializationException("Unexpected token type: " +
token.Type.ToString());
}
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
throw new NotImplementedException();
}
}
要将其插入到活页夹中，只需添加一个实例转换器到 JsonSerializerSettings 对象中的转换器列表：
To plug this into your binder, just add an instance of the converter to the Converters list in the JsonSerializerSettings object:
JsonSerializerSettings settings = new JsonSerializerSettings
{
NullValueHandling = NullValueHandling.Ignore,
MissingMemberHandling = MissingMemberHandling.Ignore,
Formatting = Formatting.None,
DateFormatHandling = DateFormatHandling.IsoDateFormat,
Converters = new List<JsonConverter> { new DecimalConverter() }
};
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