在MainLayout里面设置未登录时跳转到/login，NavigationManager会在Debug模式下抛出如下错误

"Microsoft.AspNetCore.Components.NavigationException: Exception of type 'Microsoft.AspNetCore.Components.NavigationException' was thrown.
   at Microsoft.AspNetCore.Components.Server.Circuits.RemoteNavigationManager.NavigateToCore(String uri, Boolean forceLoad)
   at Microsoft.AspNetCore.Components.NavigationManager.NavigateTo(String uri, Boolean forceLoad)

解决方案

把OnInitialized换成OnInitializedAsync

protected override async Task OnInitializedAsync()
    {
        var returnUrl = "~/" + NavigationManager.ToBaseRelativePath(NavigationManager.Uri);
        NavigationManager.NavigateTo($"/login?returnUrl={returnUrl}", true);
    }