using System;
using System.Data;
using System.Data.SqlClient;

namespace MyOA.DataAccessHelper
{
	/// <summary>
	/// 從數(shù)據(jù)庫中安全獲取數(shù)據(jù)，即當(dāng)數(shù)據(jù)庫中的數(shù)據(jù)為NULL時(shí)，保證讀取不發(fā)生異常。
	/// </summary>
	public class GetSafeData
	{
		#region DataRow

		/// <summary>
		/// 從一個(gè)DataRow中，安全得到列colname中的值：值為字符串類型
		/// </summary>
		/// <param name="row">數(shù)據(jù)行對象</param>
		/// <param name="colname">列名</param>
		/// <returns>如果值存在，返回；否則，返回System.String.Empty</returns>
		public static string ValidateDataRow_S(DataRow row,string colname)
		{
			if(row[colname]!=DBNull.Value)
				return row[colname].ToString();
			else
				return System.String.Empty;
		}

		/// <summary>
		/// 從一個(gè)DataRow中，安全得到列colname中的值：值為整數(shù)類型
		/// </summary>
		/// <param name="row">數(shù)據(jù)行對象</param>
		/// <param name="colname">列名</param>
		/// <returns>如果值存在，返回；否則，返回System.Int32.MinValue</returns>
		public static int ValidateDataRow_N(DataRow row,string colname)
		{
			if(row[colname]!=DBNull.Value)
				return Convert.ToInt32(row[colname]);
			else
				return System.Int32.MinValue;
		}

		/// <summary>
		/// 從一個(gè)DataRow中，安全得到列colname中的值：值為浮點(diǎn)數(shù)類型
		/// </summary>
		/// <param name="row">數(shù)據(jù)行對象</param>
		/// <param name="colname">列名</param>
		/// <returns>如果值存在，返回；否則，返回System.Double.MinValue</returns>
		public static double ValidateDataRow_F(DataRow row,string colname)
		{
			if(row[colname]!=DBNull.Value)
				return Convert.ToDouble(row[colname]);
			else
				return System.Double.MinValue;	
		}

		/// <summary>
		/// 從一個(gè)DataRow中，安全得到列colname中的值：值為時(shí)間類型
		/// </summary>
		/// <param name="row">數(shù)據(jù)行對象</param>
		/// <param name="colname">列名</param>
		/// <returns>如果值存在，返回；否則，返回System.DateTime.MinValue;</returns>
		public static DateTime ValidateDataRow_T(DataRow row,string colname)
		{
			if(row[colname]!=DBNull.Value)
				return Convert.ToDateTime(row[colname]);
			else 
				return System.DateTime.MinValue;	
		}
		#endregion DataRow

		#region DataReader

		/// <summary>
		/// 從SqlDataReader中安全獲取數(shù)據(jù)
		/// </summary>
		/// <param name="reader">數(shù)據(jù)讀取器SqlDataReader</param>
		/// <param name="colname">列名</param>
		/// <returns>列中的字符串?dāng)?shù)據(jù)，如果為空，則返回System.String.Empty</returns>
		public static string ValidateDataReader_S(SqlDataReader reader,string colname)
		{
			if(reader.GetValue(reader.GetOrdinal(colname))!=DBNull.Value)
				return reader.GetString(reader.GetOrdinal(colname));
			else
				return System.String.Empty;
		}

		public static int ValidateDataReader_N(SqlDataReader reader,string colname)
		{
			if(reader.GetValue(reader.GetOrdinal(colname))!=DBNull.Value)
				return reader.GetInt32(reader.GetOrdinal(colname));
			else
				return System.Int32.MinValue;
		}

		public static double ValidateDataReader_F(SqlDataReader reader,string colname)
		{
			if(reader.GetValue(reader.GetOrdinal(colname))!=DBNull.Value)
				return reader.GetDouble(reader.GetOrdinal(colname));
			else
				return System.Double.MinValue;
		}

		public static DateTime ValidateDataReader_T(SqlDataReader reader,string colname)
		{
			if(reader.GetValue(reader.GetOrdinal(colname))!=DBNull.Value)
				return reader.GetDateTime(reader.GetOrdinal(colname));
			else
				return System.DateTime.MinValue;
		}

		#endregion DataReader
	}
}