PayPal Checkout NET SDK更新带明细订单金额Patch报错咨询

• 直接传入AmountWithBreakdown对象实例报错，是因为SDK默认使用DataContractSerializer序列化Patch请求的Value字段，当Patch的泛型参数为Object时，序列化器未提前注册AmountWithBreakdown为已知类型，因此抛出类型不识别异常。
• 传入手动构造的JSON字符串报错，是因为SDK会将字符串类型的Value再次做转义序列化，最终提交到PayPal接口的是带转义符的字符串值，而非标准JSON对象，因此触发INVALID_PARAMETER_SYNTAX错误。

使用结构匹配的匿名类替代官方强类型AmountWithBreakdown作为Value赋值，匿名类无绑定DataContract特性，序列化器会直接按属性结构输出JSON，无需额外注册已知类型，是成本最低的解法。修改后的代码示例如下：

Private Function BuildPatchRequest() As List(Of Patch(Of Object))
    Dim patches = New List(Of Patch(Of Object)) From {
        New Patch(Of Object) With {
            .Op = "replace",
            .Path = "/intent",
            .Value = "CAPTURE"
        },
        New Patch(Of Object) With {
            .Op = "replace",
            .Path = "/purchase_units/@reference_id=='default'/amount",
            ' 构造和AmountWithBreakdown结构完全一致的匿名类
            .Value = New With {
                .currency_code = Me.Order.CurrencyCode,
                .value = Me.Order.Total.ToString("N2"),
                .breakdown = New With {
                    .item_total = New With {.currency_code = Me.Order.CurrencyCode, .value = Me.Order.SubTotal.ToString("N2")},
                    .tax_total = New With {.currency_code = Me.Order.CurrencyCode, .value = Me.Order.TaxTotal.ToString("N2")},
                    .shipping = New With {.currency_code = Me.Order.CurrencyCode, .value = Me.Order.ShippingTotal.ToString("N2")},
                    .discount = New With {.currency_code = Me.Order.CurrencyCode, .value = Me.Order.DiscountTotal.ToString("N2")},
                    .handling = New With {.currency_code = Me.Order.CurrencyCode, .value = Me.Order.HandlingFeeTotal.ToString("N2")},
                    .insurance = New With {.currency_code = Me.Order.CurrencyCode, .value = "0.00"},
                    .shipping_discount = New With {.currency_code = Me.Order.CurrencyCode, .value = "0.00"}
                }
            }
        }
    }
    Return patches
End Function

如果仍有序列化问题，可以先将AmountWithBreakdown对象通过JSON序列化工具转成JsonNode（System.Text.Json）或JObject（Newtonsoft.Json）对象，再赋值给Value字段，可避免序列化器识别类型的问题。

内容的提问来源于stack exchange，提问作者tbrinegar