/// <summary>
/// 检查缓存项是否达到过期时间。
/// </summary>
/// <returns>过期为 true，有效为 false。</returns>
public bool HasExpired()
{
return(ExpirationTime.Kind switch
{
DateTimeKind.Utc => DateTime.UtcNow > ExpirationTime,
DateTimeKind.Unspecified => DateTime.Now > ExpirationTime.ToLocalTime(),
_ => DateTime.Now > ExpirationTime
});