CaritasPWA/Components/OnlineStatusIndicator.razor

@using cwebplusApp.Shared.Services;

@implements IDisposable;

@inject OnlineStatusProvider OnlineStatusProvider;

<div class="row no-gutters w-100 justify-content-end" style="position: absolute;">
    @if (isOffline) {
        <MatIcon Style="padding-right:0.5rem">
            <svg xmlns="http://www.w3.org/2000/svg" height="24px" viewBox="0 0 24 24" width="24px" fill="#000000">
                <path d="M0 0h24v24H0V0z" fill="none" />
                <path d="M21 11l2-2c-3.73-3.73-8.87-5.15-13.7-4.31l2.58 2.58c3.3-.02 6.61 1.22 9.12 3.73zm-2 2c-1.08-1.08-2.36-1.85-3.72-2.33l3.02 3.02.7-.69zM9 17l3 3 3-3c-1.65-1.66-4.34-1.66-6 0zM3.41 1.64L2 3.05 5.05 6.1C3.59 6.83 2.22 7.79 1 9l2 2c1.23-1.23 2.65-2.16 4.17-2.78l2.24 2.24C7.79 10.89 6.27 11.74 5 13l2 2c1.35-1.35 3.11-2.04 4.89-2.06l7.08 7.08 1.41-1.41L3.41 1.64z" />
            </svg>
        </MatIcon>
    }
</div>


@code {

    private bool isOffline;

    public void Dispose() {
        OnlineStatusProvider.RemoveOnlineStatusChangeCallBack(OnOnlineStatusChanged);
    }

    protected override void OnInitialized() {
        base.OnInitialized();
        OnlineStatusProvider.AddOnlineStatusChangeCallBack(OnOnlineStatusChanged);
        OnOnlineStatusChanged(OnlineStatusProvider.Online);
    }

    private void OnOnlineStatusChanged(bool isOnline) {
        this.isOffline = !isOnline;
        StateHasChanged();
    }

}