Blazor.net UI 没有渲染任何东西

Question

我正在开发一个 Blaor.Net 应用程序，参考了 Internet 上许多 post 可用的内容。我面临的问题是我想将代码从 UI 移动到一个单独的文件以保持 razor 文件清晰可读和可理解。为此，我将我的 UI 侧 C# 代码保留在一个单独的组件中，该组件继承自 BaseComponent

@page "/Item"
@using WebApplication1.Shared
@using WebApplication1.Client.Services;
@inherits ItemComponent

@if (ItemList != null)
{
    <table class="table">
        <thead>
            <tr>
                <th>ID</th>
                <th>Name</th>
                <th>Category</th>
                <th>Metal</th>
                <th>Price</th>
                <th>Quantity</th>
            </tr>
        </thead>
        <tbody>
            @foreach (var item in ItemList)
            {
                <tr>
                    <td>@item.ID</td>
                    <td>@item.Name</td>
                    <td>@item.Category</td>
                    <td>@item.Metal</td>
                    <td>@item.Price</td>
                    <td>@item.Quantity</td>
                </tr>
            }
        </tbody>
    </table>
}

@functions{
    public List<ItemModel> ItemList;
    ItemComponent IC = new ItemComponent();

    protected override async Task OnInitAsync()
    {
        ItemList = IC.GetItems().Result;
    }
}

ItemComponent.cs

public class ItemComponent : ComponentBase
{
    private string BaseUrl = "http://localhost:52114/";
    public async Task<List<ItemModel>> GetItems()
    {
        HttpClient Http = new HttpClient();
        return await Http.GetJsonAsync<List<ItemModel>>(BaseUrl + "api/Item/GetItems");
    }
}

我不想在 UI 中进行 api 调用，而是希望将其放在单独的文件中，组件基本上用作此处剃刀页面的代码隐藏文件

Http.GetJsonAsync>(BaseUrl + "api/Item/GetItems");

但是在创建组件并将其继承到 razor 之后它抛出异常

System.Net.Http.HttpRequestException: No connection could be made because the target machine actively refused it. ---> System.Net.Sockets.SocketException: No connection could be made because the target machine actively refused it. at System.Net.Http.ConnectHelper.ConnectAsync(String host, Int32 port, CancellationToken cancellationToken) --- End of inner exception stack trace --- at System.Net.Http.ConnectHelper.ConnectAsync(String host, Int32 port, CancellationToken cancellationToken) at System.Threading.Tasks.ValueTask1.get_Result() at
System.Net.Http.HttpConnectionPool.ConnectAsync(HttpRequestMessage
request, Boolean allowHttp2, CancellationToken cancellationToken)

at System.Threading.Tasks.ValueTask1.get_Result() at System.Net.Http.HttpConnectionPool.CreateHttp11ConnectionAsync(HttpRequestMessage request, CancellationToken cancellationToken) at System.Threading.Tasks.ValueTask1.get_Result() at
System.Net.Http.HttpConnectionPool.GetHttpConnectionAsync(HttpRequestMessage request, CancellationToken cancellationToken) at
System.Threading.Tasks.ValueTask1.get_Result() at System.Net.Http.HttpConnectionPool.SendWithRetryAsync(HttpRequestMessage request, Boolean doRequestAuth, CancellationToken cancellationToken) at System.Net.Http.RedirectHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) at System.Net.Http.HttpClient.FinishSendAsyncUnbuffered(Task1 sendTask,
HttpRequestMessage request, CancellationTokenSource cts, Boolean
disposeCts) at System.Net.Http.HttpClient.GetStringAsyncCore(Task1 getTask) at Microsoft.AspNetCore.Builder.BlazorMonoDebugProxyAppBuilderExtensions.GetOpenedBrowserTabs(String debuggerHost) at Microsoft.AspNetCore.Builder.BlazorMonoDebugProxyAppBuilderExtensions.DebugHome(HttpContext context)

浏览器在此异常后挂起，无法关闭，只能通过任务管理器

Answer 1

所以您还有一点重构要做。正如我在回答您之前的问题时所说，您需要将所有内容从 functions 块移动到后面的代码中。使用基础 class 时，您 不应 将其与视图中的 functions 块混合。

就您的 http 调用而言，您不需要添加基础 URL 这已经为您完成，但您也不应该新建 HTTP 客户端。你应该在你的代码后面注入一个实例。

您的代码中还有其他一些小问题，因此我认为重新编写它以显示其外观可能更容易。

@page "/Item"
@inherits ItemComponent

@if (ItemList != null)
{
    <table class="table">
        <thead>
            <tr>
                <th>ID</th>
                <th>Name</th>
                <th>Category</th>
                <th>Metal</th>
                <th>Price</th>
                <th>Quantity</th>
            </tr>
        </thead>
        <tbody>
            @foreach (var item in ItemList)
            {
                <tr>
                    <td>@item.ID</td>
                    <td>@item.Name</td>
                    <td>@item.Category</td>
                    <td>@item.Metal</td>
                    <td>@item.Price</td>
                    <td>@item.Quantity</td>
                </tr>
            }
        </tbody>
    </table>
}

public class ItemComponent : ComponentBase
{

    [Inject] HttpClient HttpClient { get; set; }

    public List<ItemModel> ItemList;

    protected override async Task OnInitAsync()
    {
        ItemList = await GetItems();
    }

    public async Task<List<ItemModel>> GetItems()
    {
        return await HttpClient.GetJsonAsync<List<ItemModel>>("api/Item/GetItems");
    }
}

只要您的后端设置正确（示例：CORS），这应该会按预期工作。