Swagger传入多个查询字符串时报TypeError: NetworkError资源获取错误

• Swagger调试接口时，同时传入2个可选查询字符串参数会抛出TypeError: NetworkError when attempting to fetch resource错误
• 涉事接口共3个参数：1个路由必填参数，2个可选查询参数，仅两个可选查询参数同时传入时才会触发报错
• 完全相同的请求参数在Postman调试、直接通过浏览器地址栏发起请求时均可正常运行，无报错

[HttpGet("{customerId}/campaign/ads")]
public IActionResult GetAds([FromRoute] long customerId, [FromQuery] long? campaignId, [FromQuery] long? adGroupId)
{
    var serviceResponse = _campaignService.GetAds(new GetAdsServiceRequest
    {
        CustomerId = customerId,
        CampaignId = campaignId,
        AdGroupId = adGroupId
    });

    if (null == serviceResponse || serviceResponse.Count <= 0) return StatusCode((int)HttpStatusCode.NotFound);

    return StatusCode((int)HttpStatusCode.OK, serviceResponse.Select(googleAdsRow => new GetAdsHttpResponse
    {
        CustomerId = customerId,
        CampaignId = googleAdsRow.Campaign.Id,
        AdGroupId = googleAdsRow.AdGroup.Id,
        AdGroupAdAdId = googleAdsRow.AdGroupAd.Ad.Id,
        AdGroupAdAdName = googleAdsRow.AdGroupAd.Ad.Name,
        AdGroupAdAdType = googleAdsRow.AdGroupAd.Ad.Type.ToString()
    }));
}

这个问题是.NET平台下Swagger组件（Swashbuckle.AspNetCore）低版本的已知bug：当接口存在多个值类型的可空查询参数时，Swagger UI拼接请求URL的逻辑存在缺陷，会生成格式非法的请求地址，导致浏览器fetch请求直接抛出网络错误，请求根本没有发送到后端服务，因此Postman、直接浏览器访问这类不会触发Swagger URL拼接逻辑的场景完全正常。

• 优先升级NuGet包Swashbuckle.AspNetCore到最新稳定版本，官方已经在后续迭代中修复了多可空查询参数的URL拼接问题，绝大多数场景升级后即可直接恢复正常。
• 如果升级包后问题仍存在，显式给两个可空查询参数指定默认值、明确查询参数名称，避免OpenAPI schema生成歧义，修改后的接口签名参考如下：

[HttpGet("{customerId}/campaign/ads")]
[Produces("application/json")]
public IActionResult GetAds(
    [FromRoute] long customerId,
    [FromQuery(Name = "campaignId")] long? campaignId = null,
    [FromQuery(Name = "adGroupId")] long? adGroupId = null)
{
    // 原有业务逻辑无需改动
    var serviceResponse = _campaignService.GetAds(new GetAdsServiceRequest
    {
        CustomerId = customerId,
        CampaignId = campaignId,
        AdGroupId = adGroupId
    });

    if (null == serviceResponse || serviceResponse.Count <= 0) return NotFound();

    return Ok(serviceResponse.Select(googleAdsRow => new GetAdsHttpResponse
    {
        CustomerId = customerId,
        CampaignId = googleAdsRow.Campaign.Id,
        AdGroupId = googleAdsRow.AdGroup.Id,
        AdGroupAdAdId = googleAdsRow.AdGroupAd.Ad.Id,
        AdGroupAdAdName = googleAdsRow.AdGroupAd.Ad.Name,
        AdGroupAdAdType = googleAdsRow.AdGroupAd.Ad.Type.ToString()
    }));
}

• 排查验证：修复后可打开浏览器开发者工具（F12）的网络面板，查看Swagger发出的请求URL格式是否为标准的/{customerId}/campaign/ads?campaignId=xxx&adGroupId=xxx格式，确认无多余字符、路径参数错位问题即可。

内容的提问来源于stack exchange，提问作者omer.canyucel