JSON 选项类型的序列化

Question

我运行在为 JSON.

序列化时定义选项类型的字段时遇到了一个问题

之前工作（没有选项）

[<DataContract>]
type Article = {
    [<field: DataMemberAttribute(Name="version") >]
    version: string
}

After 抛出错误（带选项）

[<DataContract>]
type Article = {
    [<field: DataMemberAttribute(Name="version") >]
    version: string option
}

method threw exception: System.Runtime.Serialization.SerializationException: Expecting state 'Element'.. Encountered 'Text' with name '', namespace ''.

相关代码

let response = request.GetResponse() :?> HttpWebResponse
use reader = new StreamReader(response.GetResponseStream())
use memoryStream = new MemoryStream(ASCIIEncoding.Default.GetBytes(reader.ReadToEnd())) 
let result = (new DataContractJsonSerializer(typeof<Article>)).ReadObject(memoryStream) :?> Article

Answer 1

这是一个可以为 null 的定义 int。无数的 Null 引用异常证明 String 已经可以为 null...

open System
[<DataContract>]
type Person2 = {
    [<DataMember(Name="Name") >]
    entityName: Nullable<int> 
    [<DataMember(Name="Type") >]
    entityType: String
}

但是，如果您打算用一堆空值填充它，也许您应该考虑 class。这真的很可怕，但它看起来是这样的：

let p1 = { entityName =  Nullable(10); entityType = "John"}
let p2 = { entityName =  System.Nullable(); entityType = null}

val p1 : Person2 = {entityName = 10;
entityType = "John";}

val p2 : Person2 = {entityName = null;
entityType = null;}

JSON 选项类型的序列化

JSON serialization for option types

f#

datacontractjsonserializer