你不需要建立一个计时器，你可以使用内置的任务计时器一次延迟。这里是一个演示页面，显示一个警告框三秒，而不是你的图像。它显示了两种方式来设置延迟。对于简单的短时间等待使用简单。

@page "/"

<PageTitle>Index</PageTitle>

<h1>Hello, world!</h1>

@if(_loading)
{
    <div class="alert alert-info">Thanks for your business</div>
}

<div>
    <button class="btn btn-primary" disabled="@_loading" @onclick=OnLoad>Load Image</button>
    <button class="btn btn-dark" disabled="@_loading" @onclick=OnLoadAsync>Load Image</button>
</div>

@code {
    private bool _loading;

    // This way is simpler but means the task is "owned" by the Renderer
    // and the UI task doesn't complete until the delay is complete
    private async Task OnLoadAsync()
    {
        _loading = true;
        await Task.Delay(3000);
        _loading = false;
    }

    private Task _showTask = Task.CompletedTask;

    // This way hands off the wait to a task so the Ui task completes immediately 
    // and the Task is owned by the component
    private Task OnLoad()
    {
        // assign the load task to _showTask but don't await it.
        _showTask = LoadTaskAsync(3000);
        return Task.CompletedTask;
    }

    private async Task LoadTaskAsync(int millisecs)
    {
        _loading = true;
        StateHasChanged();
        await Task.Delay(millisecs);
        _loading = false;
        StateHasChanged();
    }
}