如何在C#序列化类中动态替换PayPal Orders的paymentSource字段

PayPal Advanced Checkout的v2订单请求中，payment_source下的键是动态的（比如前端传入的"paypal"或"card"），C#静态类无法直接对应这种动态结构，下面提供两种可行的实现方案：

方案1：使用Dictionary<string, object>直接定义动态结构 #

这种方式最简单直接，用字典承载payment_source的动态键值对：

定义请求模型类 #

using System.Collections.Generic;

public class OrderRequest
{
    public string intent { get; set; }
    public List<PurchaseUnit> purchase_units { get; set; }
    public Dictionary<string, object> payment_source { get; set; }
}

public class PurchaseUnit
{
    public Amount amount { get; set; }
}

public class Amount
{
    public string currency_code { get; set; }
    public string value { get; set; }
}

控制器中构造并序列化请求 #

假设前端通过请求体传入paymentSource（字符串，如"paypal"）和purchaseAmount：

using Newtonsoft.Json;

[HttpPost]
public IActionResult CreatePayPalOrder([FromBody] OrderRequestParams requestParams)
{
    // 构造订单请求对象
    var orderRequest = new OrderRequest
    {
        intent = "CAPTURE",
        purchase_units = new List<PurchaseUnit>
        {
            new PurchaseUnit
            {
                amount = new Amount
                {
                    currency_code = "USD",
                    value = requestParams.purchaseAmount
                }
            }
        },
        payment_source = new Dictionary<string, object>
        {
            // 用前端传入的变量作为键，值可根据需求填充（这里是空对象）
            { requestParams.paymentSource, new {} }
        }
    };

    // 序列化为符合PayPal要求的JSON
    string jsonRequest = JsonConvert.SerializeObject(orderRequest);
    // 后续调用PayPal API逻辑...

    return Ok(jsonRequest);
}

// 接收前端参数的模型
public class OrderRequestParams
{
    public string paymentSource { get; set; }
    public string purchaseAmount { get; set; }
}

方案2：使用JsonExtensionData特性（Newtonsoft.Json专属） #

如果希望模型结构更清晰，可通过[JsonExtensionData]特性实现动态字段的序列化：

定义带扩展数据的模型类 #

using System.Collections.Generic;
using Newtonsoft.Json;

public class OrderRequest
{
    public string intent { get; set; }
    public List<PurchaseUnit> purchase_units { get; set; }
    public PaymentSource payment_source { get; set; }
}

public class PurchaseUnit
{
    public Amount amount { get; set; }
}

public class Amount
{
    public string currency_code { get; set; }
    public string value { get; set; }
}

public class PaymentSource
{
    // 这个字典会被序列化为对象的动态属性
    [JsonExtensionData]
    private IDictionary<string, object> _additionalData;

    public PaymentSource(string paymentType)
    {
        _additionalData = new Dictionary<string, object>
        {
            { paymentType, new {} }
        };
    }
}

控制器中使用示例 #

[HttpPost]
public IActionResult CreatePayPalOrder([FromBody] OrderRequestParams requestParams)
{
    var orderRequest = new OrderRequest
    {
        intent = "CAPTURE",
        purchase_units = new List<PurchaseUnit>
        {
            new PurchaseUnit
            {
                amount = new Amount
                {
                    currency_code = "USD",
                    value = requestParams.purchaseAmount
                }
            }
        },
        payment_source = new PaymentSource(requestParams.paymentSource)
    };

    string jsonRequest = JsonConvert.SerializeObject(orderRequest);
    // 调用PayPal API逻辑...

    return Ok(jsonRequest);
}

两种方案最终序列化后的JSON都会符合PayPal要求的结构，比如当paymentSource为"paypal"时，payment_source部分会生成：

"payment_source": {
  "paypal": {}
}

内容的提问来源于stack exchange，提问作者lixid