当我启动我的应用程序时，它工作正常，但是当我更改某些内容并保存它（在哪个组件中无关紧要）时，热重载无法按预期工作，它说：
System.NullReferenceException: 'Object reference not set to an instance of an object.'
Microsoft.AspNetCore.Http.IHttpContextAccessor.HttpContext.get returned null.
System.NullReferenceException
HResult=0x80004003
Message=Object reference not set to an instance of an object.
Source=WEBv3
StackTrace:
at WEBv3.Components.Layout.NavMenu.BuildRenderTree(RenderTreeBuilder __builder) in E:\projects\e-Schedule\WEBv3\Components\Layout\NavMenu.razor:line 84
正如我所见，问题出在 HttpContextAccessor 上。据我所知，它可以工作或请求响应，也许这就是为什么它不能与热重载正常工作的原因。也许我应该做某种存储并将其存储在变量中，或者有没有办法改变 HotReload 的工作原理？
这是我的 NavMenu 组件：
@inject IHttpContextAccessor accessor
@inject ILocalStorageService LocalStorage
@inject IJSRuntime JS
@inject NavigationManager UriHelper
@using System.Net.Http;
@using System.Diagnostics;
@using System.Net;
@using Blazored.LocalStorage
@rendermode InteractiveServer
<nav class="navbar navbar-expand-lg fixed-top shadow-sm">
<div class="container-fluid">
<a class="navbar-brand" asp-controller="Home" asp-action="Index">
<img src="img/favicon.png" alt="Logo" height="32" class="d-inline-block align-text-top">
e-Schedule
</a>
<button class="navbar-toggler" type="button" data-bs-toggle="collapse" data-bs-target="#navbarNav" aria-controls="navbarNav" aria-expanded="false" aria-label="Toggle navigation">
<i class="fa-solid fa-bars"></i>
</button>
<div class="collapse navbar-collapse" id="navbarNav">
<ul class="navbar-nav me-auto">
<li class="nav-item">
<NavLink class="nav-link" href="/">
<span class="bi bi-list-nested-nav-menu" aria-hidden="true">Начало</span>
</NavLink>
</li>
<li class="nav-item">
<NavLink class="nav-link" href="SubGroup">
<span class="bi bi-list-nested-nav-menu" aria-hidden="true">Подгрупи</span>
</NavLink>
</li>
<li class="nav-item">
<a class="nav-link" asp-controller="Prepaire" asp-action="Flows">Потоци</a>
</li>
<li class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="#" data-bs-toggle="dropdown" aria-expanded="false">Меню</a>
<ul class="dropdown-menu">
<li><a class="dropdown-item" asp-controller="Home" asp-action="Index">Подменю 1</a></li>
<li><a class="dropdown-item" asp-controller="Home" asp-action="Index">Подменю 2</a></li>
</ul>
</li>
</ul>
<div class="row m-0 me-3 p-0 rounded-pill border border-1 border-secondary-subtle">
<div class="col m-0 ms-1 p-1">
<i class="fa-solid fa-sun text-secondary" style="padding-top: 3px;"></i>
</div>
<div class="col m-0 p-0">
<div class="form-check form-switch ms-2 mt-1">
<input class="form-check-input" type="checkbox" name="theme" @oninput="changeThreme" @bind="isChecked" role="switch">
</div>
</div>
<div class="col m-0 me-1 p-1">
<i class="fa-solid fa-moon text-secondary" style="padding-top: 3px;"></i>
</div>
</div>
<div class="d-flex">
<a href="https://e-organisation.uni-ruse.bg/People/Person?username=@accessor.HttpContext.User.Identity.Name.Substring(9)" target="_blank" class="person-card card text-decoration-none">
<div class="card-body row m-0 p-0">
<div class="col-2 m-0 p-0">
<div class="person-avatar m-1" style="
background: lightgray center center no-repeat;
background-size: cover;
display: block;
position: relative;
width: 35px;
height: 35px;
border-radius: 50%;
background-image: url('@bg');
">
</div>
</div>
<div class="col-10 m-0 p-0">
<p class="person-names m-1 ms-1 pt-1">@names</p>
</div>
</div>
</a>
</div>
</div>
</div>
</nav>
@code {
// Internal field holding checkbox state
private bool isChecked { get; set; }
const string e_organisation_url = "";
const string e_organisation_api_url = "";
string username = "";
private string bg { get; set; }
string names = "";
private async void changeThreme()
{
if (isChecked == false){
isChecked = true;
await JS.InvokeVoidAsync("eval", $"document.documentElement.setAttribute('data-bs-theme', 'dark')");
await LocalStorage.SetItemAsStringAsync("theme", "dark");
}
else if(isChecked == true){
isChecked = false;
await JS.InvokeVoidAsync("eval", $"document.documentElement.setAttribute('data-bs-theme', 'light')");
await LocalStorage.SetItemAsStringAsync("theme", "light");
}
}
protected override async Task OnInitializedAsync()
{
username = accessor.HttpContext.User.Identity.Name.Substring(9);
try
{
using HttpClientHandler handler = new()
{
UseDefaultCredentials = true,
PreAuthenticate = true,
Credentials = CredentialCache.DefaultNetworkCredentials
};
// HttpClient with the configured handler
using HttpClient httpClient = new(handler);
// Call API and get person object data
HttpResponseMessage httpResponse = await httpClient.GetAsync($"{e_organisation_api_url}Person/{username}/Data");
httpResponse.EnsureSuccessStatusCode();
var json = await httpResponse.Content.ReadAsStringAsync();
dynamic personData = Newtonsoft.Json.Linq.JObject.Parse(json);
bg = $"{e_organisation_url}uploads/avatars/{personData.avatar}";
names = personData.personNames;
}
catch (Exception ex)
{
// Handle exceptions here, log them, display an error message, etc.
Console.WriteLine($"An error occurred: {ex.Message}");
}
}
}
我尝试创建一个局部变量，结果是一样的。也许我应该做一些实用类idk。我正在使用 Visual Studio 2022。
只需更改框架并使用 PHP 即可。在过去 10 年里，我在各种项目中使用 PHP 都没有遇到任何问题。