.NET 6中在AuthenticationStateProvider使用Blazored.LocalStorage的构造函数问题

问题场景 #

在Blazor WebAssembly项目中，尝试实现自定义CustomAuthStateProvider，通过注入ILocalStorageService读取本地存储的认证状态来构建AuthenticationState，但运行应用时触发错误：

无法找到BlazorBattles.Client.CustomAuthStateProvider的合适构造函数，需确保类型为具体类型且公共构造函数的所有参数已注册服务

移除构造函数和ILocalStorageService相关引用后程序可正常运行，添加后就会触发上述错误。

相关代码 #

CustomAuthStateProvider.cs #

public class CustomAuthStateProvider : AuthenticationStateProvider
{
    private readonly ILocalStorageService _localStorageService;
    CustomAuthStateProvider(ILocalStorageService localStorageService)
    {
        _localStorageService = localStorageService;
    }

    public override async Task<AuthenticationState> GetAuthenticationStateAsync()
    {
        if (await _localStorageService.GetItemAsync<bool>("isAuthenticated"))
        {
            ClaimsIdentity claimsIdentity = new ClaimsIdentity(new[]
            {
                new Claim(ClaimTypes.Name, "Thomas")
            }, "Test Authentication");

            ClaimsPrincipal user = new ClaimsPrincipal(claimsIdentity);
            AuthenticationState state = new AuthenticationState(user);

            // 通知所有组件认证状态已变更
            NotifyAuthenticationStateChanged(Task.FromResult(state));
            return (state);
        }

        // 返回未授权用户（无ClaimsIdentity）
        return (new AuthenticationState(new ClaimsPrincipal()));
    }
}

Program.cs #

using BlazorBattles.Client;
using BlazorBattles.Client.Services;
using Microsoft.AspNetCore.Components.Web;
using Microsoft.AspNetCore.Components.WebAssembly.Hosting;
using Blazored.Toast;
using Blazored.LocalStorage;
using Microsoft.AspNetCore.Components.Authorization;

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

builder.Services.AddBlazoredToast();
builder.Services.AddBlazoredLocalStorage();
builder.Services.AddScoped(sp => new HttpClient { BaseAddress = new Uri(builder.HostEnvironment.BaseAddress) });
builder.Services.AddScoped<IBananaService, BananaService>();
builder.Services.AddScoped<IUnitService, UnitService>();
builder.Services.AddScoped<AuthenticationStateProvider, CustomAuthStateProvider>();
builder.Services.AddOptions();
builder.Services.AddAuthorizationCore();

await builder.Build().RunAsync();

使用版本 #

• Blazored.LocalStorage V4.3.0
• Microsoft.AspNetCore.Components.Authorization V6

错误原因 #

CustomAuthStateProvider的构造函数未添加public修饰符，C#中类成员默认访问级别为private，导致依赖注入容器无法访问该构造函数来实例化对象并注入ILocalStorageService。

解决方案 #

为CustomAuthStateProvider的构造函数添加public关键字，让DI容器能够正常调用构造函数完成依赖注入：

public class CustomAuthStateProvider : AuthenticationStateProvider
{
    private readonly ILocalStorageService _localStorageService;
    // 添加public修饰符
    public CustomAuthStateProvider(ILocalStorageService localStorageService)
    {
        _localStorageService = localStorageService;
    }

    // 其余代码保持不变...
}

内容的提问来源于stack exchange，提问作者ThomasRogers