/// <summary>
/// @useridをクリックしたとき
/// </summary>
/// <param name="screenName">スクリーンネーム</param>
private async void SelectMention(string screenName)
{
var user = await AccountTokens.ShowUserAsync(this.TimelineModel.TokenSuffix, screenName);
this.TimelineModel.ShowUserTimeline(new UserOverviewProperties(user));
}