如何为现有查询字符串 Blazor 设置新值

Question

我正在尝试更改查询字符串参数而不重新加载页面。我有一个

DateTime

日期值，我试图将其转换为字符串并放入 url 中。为了这个问题，说吧：

DateTime? Date = new DateTime(2020, 9, 4);

所以，我的网址可能看起来像：

https://localhost:44346/Events?d=2020-10-18

在我做了任何必须做的魔法之后，结果是这样的：

https://localhost:44346/Events?d=2020-10-04

我尝试使用

NavigationManager

和

QueryHelpers

如下所示，但我没有运气：

QueryHelpers.AddQueryString(navManager.Uri, "d", Date?.ToString("yyyy-MM-dd"));

Answer 1

请查看此演示

    @page "/counter"
    @using Microsoft.AspNetCore.WebUtilities
    @using System.Web 
    @inject NavigationManager navManager
    
    <button class="btn btn-primary" @onclick="ChangeUrl">Change url</button>
    <br />
    demonstrate lack of page reload
    <br />
    <button class="btn btn-primary" @onclick="AddItem">Add item</button>
    @foreach (var item in list)
    {
        @item
    }
    
    @code {
    
        private List<string> list = new List<string>()
        {
            "Test string"
        };
    
        private void AddItem()
        {
            var uri = navManager.ToAbsoluteUri(navManager.Uri);
    
            if (QueryHelpers.ParseQuery(uri.Query).TryGetValue("d", out var param))
            {
                list.Add(param.First());
            }
            else
            {
                list.Add("d is empty");
            }
        }
    
        DateTime dateCounter = DateTime.Today;
        private void ChangeUrl()
        {
            dateCounter = dateCounter.AddDays(1);
    
            string url = RemoveQueryStringByKey(navManager.Uri, "d");
            var query = new Dictionary<string, string> { { "d", dateCounter.ToString("dd-MM-yyyy") } };
    
            navManager.NavigateTo(QueryHelpers.AddQueryString(url, query));
        }
    
        public static string RemoveQueryStringByKey(string url, string key)
        {
            var uri = new Uri(url);
    
            // this gets all the query string key value pairs as a collection
            var newQueryString = HttpUtility.ParseQueryString(uri.Query);
    
            // this removes the key if exists
            newQueryString.Remove(key);
    
            // this gets the page path from root without QueryString
            string pagePathWithoutQueryString = uri.GetLeftPart(UriPartial.Path);
    
            return newQueryString.Count > 0
                ? String.Format("{0}?{1}", pagePathWithoutQueryString, newQueryString)
                : pagePathWithoutQueryString;
        }
    }