异步方法没有从razor组件中执行

Question

我有一个服务器端Blazor应用程序，在'app.razor'中我有:

<CascadingAuthenticationState>
<Router AppAssembly="@typeof(Program).Assembly" PreferExactMatches="@true">
<Found Context="routeData">
<AuthorizeRouteView RouteData="@routeData" DefaultLayout="@typeof(MainLayout)">
<NotAuthorized>
@(myService.Login())
</NotAuthorized>
<Authorizing>
<p>Bitte warten...</p>
</Authorizing>
</AuthorizeRouteView>
</Found>
<NotFound>
<LayoutView Layout="@typeof(MainLayout)">
<p>Sorry, there's nothing at this address.</p>
</LayoutView>
</NotFound>
</Router>
</CascadingAuthenticationState>

这是我的服务:

public class MyService : IMyService
{
protected readonly HttpClient httpClient;
public MyService(
HttpClient httpClient)
{
this.httpClient = httpClient;
}
public async Task Login()
{
await httpClient.GetAsync(loginUrl);
}
}

按如下方式注册服务:

services.AddHttpClient<IMyService, MyService>(client => 
{ 
client.BaseAddress = new Uri(someUrl); 
});

然而，我得到以下错误运行:

System.Runtime.CompilerServices。AsyncTaskMethodBuilder1+AsyncStateMachineBox1[System.Threading.Tasks.VoidTaskResult,App.Services.MyService+d__5]

我做错了什么?

Answer 1

lot…

NotAuthorized应该是这样的:

<NotAuthorized>
@if (!context.User.Identity.IsAuthenticated)
{
<RedirectToLogin />
}
else
{
<p>You are not authorized to access this resource.</p>
}
</NotAuthorized>

在if子句中检查用户是否经过身份验证。如果没有，你把他重定向到RedirectToLogin组件。这里没有调用服务方法。

在else子句中显示一条消息…这样做是因为用户可以通过身份验证，但他仍然没有被授权访问资源。

RedirectToLogin.razor

@inject myService myService
Put here html elements to gather the users' credentials with a "Login" 
button, which when clicked, calls myService.Login() method to autenticate the 
user.
@code
{
// Note: this code sample demonstrate how to login a user when you use 
// Asp.Net Core Identity. It is not clear what identity system are you using
protected override void OnInitialized()
{
ReturnUrl = "~/" + ReturnUrl;
NavigationManager.NavigateTo($"Identity/Account/Login?returnUrl= 
{ReturnUrl}", forceLoad:true);
}
}

注意:此表达式:@(myService.Login())被求值为System.Threading.Tasks.VoidTaskResult，从而导致错误。你应该使用return await httpClient.GetAsync(loginUrl); instead