在按钮上执行异步方法单击 Blazor 服务器

Question

我试图在按下按钮时执行异步方法。代码编译没有问题，但是当按钮被点击时，该方法永远不会被调用。我已经使用了我可以使用的所有 google fu，但无济于事。我在语法上做错了吗？是我忘记导入某些东西还是我误解了它的工作原理？

  @foreach (Data.Course cor in CourseList)
                    { 
/...
<button class="btn btn-outline-primary" @onclick="@(async () => await EnrollCourse(cor.CourseId))">
                                        Enroll
                                    </button>
}

@functions{
    private async Task EnrollCourse(int corid)
    {
        var authState = await AuthenticationStateProvider.GetAuthenticationStateAsync();
        string userid = authState.User.Identity.Name;
        await _db.EnrollCourse(corid, userid);
        NavigationManager.NavigateTo($"/course/{corid}");
        
    }



}

Answer 1

对于在 google 上遇到此问题的任何人，我最终将按钮设置为重定向到运行代码并重定向到最终页面的不同页面。

<div class="button">
    <a href="/enroll/@cor.CourseId">Enroll</a>
</div>

@page "/enroll/{course}"
@inject Data.CourseData _db
@inject NavigationManager NavigationManager
@inject AuthenticationStateProvider AuthenticationStateProvider
@inject Microsoft.AspNetCore.Identity.UserManager<Microsoft.AspNetCore.Identity.IdentityUser> userManager
@using System.Security.Claims


@code {
    [Parameter]
    public string course { get; set; }
    protected override async Task OnInitializedAsync()
    {
        var authState = await AuthenticationStateProvider.GetAuthenticationStateAsync();

        var user = await userManager.GetUserAsync(authState.User);
        if (user != null)
        {
            string userid = user.Id;
            await _db.EnrollCourse(Int32.Parse(course), userid);
            NavigationManager.NavigateTo("/course/" + Int32.Parse(course));


        }
    }

}

Answer 2

请注意我是如何收集用户 ID 的。我希望这有帮助。您的用户管理器也可能是 UserManager<ApplicationUser> 类型...

    @inject UserManager<ApplicationUser> userManager
    @using System.Security.Claims
    .....
    <AuthorizeView>
          @foreach (Data.Course cor in CourseList)
                    { 
/...
<button class="btn btn-outline-primary" @onclick="@(async () => await EnrollCourse(cor.CourseId,context.User))">
                                        Enroll
                                    </button>
}
    </AuthorizeView>
@functions{
     private async Task EnrollCourse(int corid, ClaimsPrincipal identity)
     {

        var user = await userManager.GetUserAsync(identity);

        var userid = user.Id;
        await _db.EnrollCourse(corid, userid);
        NavigationManager.NavigateTo($"/course/{corid}");
        
     }



}