/// <summary>
/// 获取，只适用于主键为Id的获取
/// </summary>
/// <param name="id"></param>
/// <param name="viewName">试图名</param>
/// <returns></returns>
public T GetItem(long id, string viewName = "")
{
string condition = "AND Id = @Id";
return(_provider.GetItem <T>(condition, new { Id = id }, viewName));
}