我们可以在Startup.cs文件的ConfigureServices方法内配置一个HttpMessageHandlerBuilder扩展方法，该方法将拦截所有命名HttpClient发送的请求，并默认添加查询参数。具体代码如下：

services.AddHttpClient("MyNamedClient")
    .ConfigureHttpClient((serviceProvider, client) =>
    {
        var httpContextAccessor = serviceProvider.GetService();
        client.BaseAddress = new Uri("https://example.com/");

        if (httpContextAccessor != null && httpContextAccessor.HttpContext != null)
        {
            // 获取请求的查询参数并添加到请求中
            var query = httpContextAccessor.HttpContext.Request.Query;
            foreach (var item in query)
            {
                client.DefaultRequestHeaders.Add(item.Key, item.Value);
            }
        }
    });

在上述代码中，我们使用了HttpClientFactory来创建命名HttpClient，并通过ConfigureHttpClient方法设置了基础地址和默认请求头。通过获取IHttpContextAccessor服务，我们可以获取当前请求所带的查询参数，然后将其添加到 HttpClient 的 DefaultRequestHeaders中作为默认请求参数。

这样，在我们向命名HttpClient发送请求时，查询参数将被默认添加到请求中。

示例代码：

public class MyController : Controller
{
    private readonly IHttpClientFactory _httpClientFactory;

    public MyController(IHttpClientFactory httpClientFactory)
    {
        _httpClientFactory = httpClientFactory;
    }

    public async Task Index()
    {
        var httpClient = _httpClientFactory.CreateClient("MyNamedClient");
        var response = await httpClient.GetAsync("myApi?param1=value1¶m2=value2");
        // ...
    }
}