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max's questions

Martin Hope
max
Asked: 2025-01-12 09:15:19 +0800 CST
  • 7

我有一个 ASP.NET Core Web API 项目作为后端，还有一个 Blazor Web 程序集作为前端。

Web API 可ProductController返回 JSON 数据（产品、组等）。Blazor 应用使用该 API。

ProductService我在 Blazor 端创建。ProductService获取HttpClient构造函数注入并向 API 发送请求。这就是问题所在——我收到 404 NotFound 错误。当我使用注入HttpClient或直接在页面上创建它时，它可以工作（请参阅下面显示的代码）。

如果我在浏览器中输入 API URL，我会得到数据（产品目录）。我HttpClient按照 Microsoft在文章中所说的进行初始化。请帮助解决这个问题。

这是 Blazor 初始化代码：

var builder = WebAssemblyHostBuilder.CreateDefault(args);
builder.RootComponents.Add<App>("#app");
builder.RootComponents.Add<HeadOutlet>("head::after");

builder.Configuration.AddJsonFile("appsettings.json", optional: false, reloadOnChange: true);
var appSettings = builder.Configuration.Get<AppSettings>();
builder.Services.AddSingleton<AppSettings>(appSettings);

builder.Services.AddBlazoredLocalStorage();

builder.Services.AddHttpClient("Shop.WebApi", client => client.BaseAddress =
    new Uri(appSettings.ApiBaseUri))
         .AddHttpMessageHandler<CustomAuthorizationMessageHandler>();
builder.Services.AddScoped<CustomAuthorizationMessageHandler>();
builder.Services.AddScoped(sp => sp.GetRequiredService<IHttpClientFactory>().CreateClient("Shop.WebApi"));
builder.Services.AddApiAuthorization();

builder.Services.AddScoped<CustomAuthenticationStateProvider>();
builder.Services.AddScoped<AuthenticationStateProvider>(
    provider => provider.GetRequiredService<CustomAuthenticationStateProvider>());
builder.Services.AddScoped<AuthService>();
builder.Services.AddHttpClient<IProductService, HttpProductService>(client =>
{
    client.BaseAddress = new Uri(appSettings.ApiBaseUri);
}).AddHttpMessageHandler<CustomAuthorizationMessageHandler>();

await builder.Build().RunAsync();

这是产品目录页面：

@inject IProductService ProductService
@inject HttpClient TheHttpClient
...
protected override async Task OnInitializedAsync()
{
    try
    {
    // this works   
        _ProductCatalog = await TheHttpClient.GetFromJsonAsync<ProductCatalog>("api/Product/GetProductCatalog");
    // this doesn't work
        //await LoadProductCatalogAsync();
    }
    catch (Exception ex)
    {
        Console.WriteLine("An error occurred while initializing the page: " + ex.Message);
    }
}

private async Task LoadProductCatalogAsync()
{
    try
    {
        _ProductCatalog = await ProductService.GetProductCatalog();
    }
    catch (Exception ex)
    {
        Console.WriteLine("An error occurred while loading the product catalog: " + ex.Message);
    }
}

产品服务：

public class HttpProductService : IProductService
{
    public HttpProductService(HttpClient httpClient)
    {
        TheHttpClient = httpClient;
    }

    public async Task<ProductCatalog> GetProductCatalog()
    {        
        var response = await TheHttpClient.GetAsync($"{GetApiBaseUri()}");

        if (response.IsSuccessStatusCode)
        {
            return await response.Content.ReadFromJsonAsync<ProductCatalog>();
        }

        return new ProductCatalog();
    }

    protected virtual string GetApiBaseUri() => $"api/Product";
    protected HttpClient TheHttpClient { get; }
}
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