csharp: DBNull and DateTime

/// <summary>    ///     /// </summary>    /// <param name="dateTime"></param>    /// <returns></returns>    public DateTime CheckDBNull(object dateTime)    {      if (dateTime == DBNull.Value)        return DateTime.MinValue;      else        return (DateTime)dateTime;    }    /// <summary>    ///     /// </summary>    /// <param name="field"></param>    /// <param name="data"></param>    /// <returns></returns>    public DateTime? ReadNullableDateTimefromReader(string field, IDataRecord data)    {      var a = data[field];      if (a != DBNull.Value)      {        return Convert.ToDateTime(a);      }      return null;    }    /// <summary>    ///     /// </summary>    /// <param name="field"></param>    /// <param name="data"></param>    /// <returns></returns>    public DateTime ReadDateTimefromReader(string field, IDataRecord data)    {      DateTime value;      var valueAsString = data[field].ToString();      try      {        value = DateTime.Parse(valueAsString);      }      catch (Exception)      {        throw new Exception("Cannot read Datetime from reader");      }      return value;    }	}

menu.IsMainMenu = (!DBNull.Equals(reader["IsMainMenu"], null)) ? (bool)reader["IsMainMenu"] : true;            menu.Remark = (!DBNull.Equals(reader["Remark"], null)) ? (string)reader["Remark"].ToString() : "";            menu.ParentMenuId = (!DBNull.Equals(reader["ParentMenuId"], null)) ? (int)reader["ParentMenuId"] : 0;            menu.TreeLevel = (!DBNull.Equals(reader["TreeLevel"], null)) ? (int)reader["TreeLevel"] : 0;            menu.SortIndex = (!DBNull.Equals(reader["SortIndex"], null)) ? (int)reader["SortIndex"] : 0;            menu.CreatedOn = CheckDBNull(reader["CreatedOn"]);// (!object.Equals(reader["CreatedOn"], null)) ? (DateTime)reader["CreatedOn"] : DateTime.Now;

原标题：csharp: DBNull and DateTime

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