using Microsoft.AspNetCore.Http.Extensions;
using Microsoft.AspNetCore.WebUtilities;

public IActionResult About()
{
    string currentFullUrl = $"{Request.Scheme}://{Request.Host}{Request.Path}{Request.QueryString}";            
    var uri = new Uri(currentFullUrl);
    var baseUri = uri.GetComponents(UriComponents.Scheme | UriComponents.Host | UriComponents.Port | UriComponents.Path, UriFormat.UriEscaped);
    var query = QueryHelpers.ParseQuery(uri.Query);
    var items = query.SelectMany(x => x.Value, (col, value) => new KeyValuePair<string, string>(col.Key, value)).ToList();
    var pageItem = items.FirstOrDefault(i => i.Key == "page"); // 是可以有多个的哦.
    if (pageItem.Key != null) // 判断是否有 
    {
        int page = Convert.ToInt32(pageItem.Value); 
    }
    items.RemoveAll(x => x.Key == "key");  
    items.RemoveAll(x => x.Key == "key" && x.Value == "value");  
    var qb = new QueryBuilder(items);
    qb.Add("newKey", "newValue");
    var newUrl = baseUri + qb.ToQueryString();
    return View();
}