ASP.NET Core连接localhost API遇Connection refused错误求助

错误信息 #

System.Net.Http.HttpRequestException: Connection refused. (localhost:7146)

补充说明 #

项目需求是给Category表添加新数据。在给CategoryController1.cs添加HttpGet和HttpPost操作之前，应用可正常运行：按Ctrl+F5启动后，能从Index.cshtml页面通过Ctrl+Shift+W导航到设计页面。但添加完这些操作后，直接从Index.cshtml运行应用时，在以下位置报错：

SignalRWebUI.Controllers.CategoryController1.Index() in CategoryController1.cs + var responseMessage = await client.GetAsync("https://localhost:7146/api/Category");

相关代码片段 #

1. CategoryController1.cs #

public class CategoryController1 : Controller
{
    private readonly IHttpClientFactory _httpClientFactory;

    public CategoryController1(IHttpClientFactory httpClientFactory)
    {
        _httpClientFactory = httpClientFactory;
    }

    public async Task<IActionResult> Index()
    {
        var client = _httpClientFactory.CreateClient();
        var responseMessage = await client.GetAsync("https://localhost:7146/api/Category");
        if(responseMessage.IsSuccessStatusCode) 
        {
            var jsonData=await responseMessage.Content.ReadAsStringAsync();
            var values =JsonConvert.DeserializeObject<List<ResultCategoryDto>>(jsonData);//Verileri çekme için 
            return View(values);
        }
        return View();
    }

    [HttpGet]
    public IActionResult CreateCategory()
    {
        return View();
    }

    [HttpPost]
    public async  Task<IActionResult> CreateCategory(CreateCategoryDto createCategoryDto)
    {
        createCategoryDto.Status = true;
        var client= _httpClientFactory.CreateClient();
        var jsonData = JsonConvert.SerializeObject(createCategoryDto);
        StringContent stringContent = new StringContent(jsonData,Encoding.UTF8,"application/json");
        var responseMessage = await client.PostAsync("https://localhost:7146/api/Category",stringContent);
        if(responseMessage.IsSuccessStatusCode)
        {
            return RedirectToAction("Index");
        }
        return View();
    }
 }

2. Index.cshtml #

@model List<SignalRWebUI.Dtos.CategoryDtos.ResultCategoryDto>
@{
    ViewData["Title"] = "Index";
    Layout = "~/Views/AdminLayoutController1/Index.cshtml";
}

<div class="content">
   <div class="container-fluid">
    <h4 class="page-title">Kategori İşlemleri</h4>
    <div class="row">
        <div class="col-md-12">
            <div class="card">
                <div class="card-header">
                    <div class="card-title">Kategori Listesi</div>
                </div>
                <div class="card-body">
                    <div class="card-sub">
                        Kategori ile ilgili işlemleri aşağıdan gerçekleştirebilirsiniz :
                    </div>
                    <table class="table mt-3">
                        <thead>
                            <tr>
                                <th scope="col">#</th>
                                <th scope="col">Kategori Adı</th>
                                <th scope="col">Durum</th>
                                <th scope="col">Sil</th>
                                <th scope="col">Güncelle</th>
                            </tr>
                        </thead>
                        <tbody>
                            @foreach(var item in Model)
                            {
                                <tr>
                                    <td>@item.CategoryID</td>
                                    <td>@item.CategoryName</td>
                                    <td>@item.Status</td>
                                    <td><a href="#" class="btn btn-outline-danger" >Sil</a> </td>
                                    <td><a href="#" class="btn btn-outline-success" >Günelle</a> </td>
                                </tr>
                            }
                        </tbody>
                    </table>
                    <a href="/Category/CreateCategory/" class="btn btn-outline-primary">Yeni Kategori Girişi</a>
                </div>
            </div> 
        </div>
    </div>
</div>

排查与解决步骤 #

• 确认API服务已启动：https://localhost:7146/api/Category对应的后端API项目必须先启动运行，否则会触发连接拒绝。直接在浏览器访问该API地址，验证是否能正常返回数据；同时检查API项目的启动配置，确认监听端口确实是7146。
• 检查端口占用情况：用命令netstat -ano | findstr :7146查看7146端口是否被其他程序占用。若被占用，可关闭占用程序，或修改API项目的监听端口。
• 验证API路由正确性：确保后端API的Category控制器存在对应的[HttpGet]接口，路由路径/api/Category无拼写错误（包括大小写、路径层级）。
• 调整项目启动顺序：若WebUI和API是两个独立项目，需先启动API项目，再启动WebUI；也可在解决方案中设置多个启动项目，让两者同时启动。
• 排查HTTPS证书问题：若API使用HTTPS，需确保WebUI项目信任API的开发证书。可临时改用HTTP地址测试（若API支持），或手动将API证书导入系统信任存储。
• 优化HttpClient配置：避免硬编码API地址，将地址配置在appsettings.json中；同时检查IHttpClientFactory的配置，确认无超时、代理等影响连接的异常参数。

内容的提问来源于stack exchange，提问作者omertascan