如何为现有查询字符串 Blazor 设置新值

Question

我试图在不重新加载页面的情况下更改查询字符串参数。我有一个 DateTime 日期值，我试图将其转换为字符串并放入 url。说，为了这个问题，它是：

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

所以，我的 url 可能开始看起来像：

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

在我完成所有必须完成的魔术之后，结果如下：

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

我曾尝试像下面这样使用 NavigationManager 和 QueryHelpers，但我没有成功：

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;
    }
}

如何为现有查询字符串 Blazor 设置新值

How to set new value to existing query string Blazor

asp.net-core

url

query-string

blazor