为什么在 Razor 组件生产中抛出 Null 引用？

Question

我有测试代码

@page "/admin/userInfo"
@page "/admin"
@inherits OwningComponentBase<UserManager<IdentityUser>>
@inject AuthenticationStateProvider AuthenticationStateProvider

@functions
{

}

@code
{
   public UserManager<IdentityUser> _userManager => Service;
   public string userName; /* => AuthenticationStateProvider.GetAuthenticationStateAsync().Result.User.Identity.Name; */

   public IdentityUser identity;

   protected override async Task OnInitializedAsync(){
    if (_userManager != null)
    {   
        identity = await _userManager.FindByNameAsync(userName);
    userName = "abcde";
    }
    Console.WriteLine("OnInitializedAsync");
    }
}

<h4>User Information</h4>
<h2>User name: @userName</h2>
<h4>h4 tag</h4>
@* <p>@identity.UserName</p> *@

当我尝试获取身份值时，OnInitializedAsync 中的用户名或身份无法跟上创建的速度。我认为当 OnInitializedAsync 结束时 @userName 或 @identity.UserName 可以访问 html 标签。我该如何解决这个问题？谢谢你的帮助

我尝试获取一些在 OnInitializedAsync 方法中初始化的值，但方法的执行无法到达组件的创建。我该如何解决这个问题？

Answer 1

您可以尝试下面的代码：

@page "/admin/userInfo"
@page "/admin"
@inherits OwningComponentBase<UserManager<IdentityUser>>
@inject AuthenticationStateProvider AuthenticationStateProvider

@code
{
   public UserManager<IdentityUser> _userManager => Service;
   public string userName;
   public IdentityUser identity;

   protected override async Task OnInitializedAsync()
   {
       var authState = await AuthenticationStateProvider.GetAuthenticationStateAsync();
       var user = authState.User;

       if (user.Identity.IsAuthenticated)
       {
           userName = user.Identity.Name;
           identity = await _userManager.FindByNameAsync(userName);
       }
       else
       {
           // Handle the case where the user is not authenticated if necessary
       }
   }
}

<h4>User Information</h4>
@if(identity != null)
{
   <h2>User name: @identity.UserName</h2>
}
else
{
   <p>User is not authenticated.</p>
}
<h4>h4 tag</h4>