再不用担心DataRow类型转换和空值了（使用扩展方法解决高频问题）
在使用DataRow读取数据时，通常会遇到数据可能为Null, 但是又需要转换为如int等其它类型的数据，因此就通常会写这样的代码：
if (dr[name] != DBNull.Value && dr[name] != null)
{
if (!int.TryParse(dr[name].ToString(), out result))
throw new Exception("整形转换失败");
}
而且这样的代码通常会大段大段出现在很多地方。
对于比较懒惰的程序员来说，这样的RY(repeat yourself)是一件很痛苦的事情，因此是时候来想个更好的方法了。这里首先想到的就是Extension Method。
很简单的几句代码，有了这个方法之后，在使用DataRow时，就可以通过扩展方法读取数据了
model.Id = dr.SafeRead<Int32>("Id",0);
model.codeNum = dr.GetString("codeNum");
简单但是实用的代码，希望对大家在项目中有所帮助。
这里参考了,一下两篇文章，并进行了代码重新组织，最后是整理后类源码
使用 Extension Methods 来使 IDataReader 更加方便
public static class SystemDataExtension
{
#region DataReader 扩展
public static T SafeRead<T>(this IDataReader reader, string fieldName, T defaultValue)
{
try
{
object obj = reader[fieldName];
if (obj == null || obj == System.DBNull.Value)
return defaultValue;
return (T)Convert.ChangeType(obj, defaultValue.GetType());
}
catch
{
return defaultValue;
}
}
/// <summary>
/// 获取字符串类型数据
/// </summary>
/// <param name="dr"></param>
/// <param name="name"></param>
/// <returns></returns>
public static string GetString(this IDataReader dr, string name)
{
if (dr[name] != DBNull.Value && dr[name] != null)
return dr[name].ToString();
return String.Empty;
}
/// <summary>
/// 获取非空类型数据
/// </summary>
/// <param name="con"></param>
/// <param name="name"></param>
/// <returns></returns>
public static DateTime GetDateTime(this IDataReader dr, string name)
{
DateTime result = DateTime.Now;
if (dr[name] != DBNull.Value && dr[name] != null)
{
if (!DateTime.TryParse(dr[name].ToString(), out result))
throw new Exception("日期格式数据转换失败");
}
return result;
}
/// <summary>
/// 获取可空类型日期数据
/// </summary>
/// <param name="dr"></param>
/// <param name="name"></param>
/// <returns></returns>
public static DateTime? GetNullDateTime(this IDataReader dr, string name)
{
DateTime? result = null;
DateTime time = DateTime.Now;
if (dr[name] != DBNull.Value && dr[name] != null)
{
if (!DateTime.TryParse(dr[name].ToString(), out time))
throw new Exception("日期格式数据转换失败");
result = time;
}
return result;
}
/// <summary>
/// 获取guid类型数据
/// </summary>
/// <param name="dr"></param>
/// <param name="name"></param>
/// <returns></returns>
public static Guid GetGuid(this IDataReader dr, string name)
{
Guid guid = Guid.Empty;
if (dr[name] != DBNull.Value && dr[name] != null)
{
if (Guid.TryParse(dr[name].ToString(), out guid))
throw new Exception("guid类型数据转换失败");
}
return guid;
}
/// <summary>
/// 获取整形数据
/// </summary>
/// <param name="dr"></param>
/// <param name="name"></param>
/// <returns></returns>
public static int GetInt32(this IDataReader dr, string name)
{
int result = 0;
if (dr[name] != DBNull.Value && dr[name] != null)
{
if (!int.TryParse(dr[name].ToString(), out result))
throw new Exception("整形转换失败");
}
return result;
}
/// <summary>
/// 获取双精度类型数据
/// </summary>
/// <param name="dr"></param>
/// <param name="name"></param>
/// <returns></returns>
public static double GetDouble(this IDataReader dr, string name)
{
double result = 0.00;
if (dr[name] != DBNull.Value && dr[name] != null)
{
if (!double.TryParse(dr[name].ToString(), out result))
throw new Exception("双精度类型转换失败");
}
return result;
}
/// <summary>
/// 获取单精度类型数据
/// </summary>
/// <param name="dr"></param>
/// <param name="name"></param>
/// <returns></returns>
public static float GetSingle(this IDataReader dr, string name)
{
float result = 0.00f;
if (dr[name] != DBNull.Value && dr[name] != null)
{
if (!float.TryParse(dr[name].ToString(), out result))
throw new Exception("单精度类型转换失败");
}
return result;
}
/// <summary>
/// 获取decimal类型数据
/// </summary>
/// <param name="dr"></param>
/// <param name="name"></param>
/// <returns></returns>
public static decimal GetDecimal(this IDataReader dr, string name)
{
decimal result = 0.00m;
if (dr[name] != DBNull.Value && dr[name] != null)
{
if (!decimal.TryParse(dr[name].ToString(), out result))
throw new Exception("Decimal类型转换失败");
}
return result;
}
/// <summary>
/// 获取int16类型数据
/// </summary>
/// <param name="dr"></param>
/// <param name="name"></param>
/// <returns></returns>
public static Int16 GetInt16(this IDataReader dr, string name)
{
short result = 0;
if (dr[name] != DBNull.Value && dr[name] != null)
{
if (!short.TryParse(dr[name].ToString(), out result))
throw new Exception("短整形转换失败");
}
return result;
}
/// <summary>
/// 获取Byte类型数据
/// </summary>
/// <param name="dr"></param>
/// <param name="name"></param>
/// <returns></returns>
public static byte GetByte(this IDataReader dr, string name)
{
byte result = 0;
if (dr[name] != DBNull.Value && dr[name] != null)
{
if (!byte.TryParse(dr[name].ToString(), out result))
throw new Exception("Byte类型转换失败");
}
return result;
}
/// <summary>
/// 获取bool类型数据如果传值是1或者是返回true;
/// </summary>
/// <param name="con"></param>
/// <param name="name"></param>
/// <returns></returns>
public static bool GetBool(this IDataReader dr, string name)
{
if (dr[name] != DBNull.Value && dr[name] != null)
{
return dr[name].ToString() == "1" || dr[name].ToString() == "是" || dr[name].ToString().ToLower() == "true";
}
return false;
}
#endregion
#region DataRow 扩展
public static T SafeRead<T>(this DataRow dr, string fieldName, T defaultValue)
{
try
{
object obj = dr[fieldName];
if (obj == null || obj == System.DBNull.Value)
return defaultValue;
return (T)Convert.ChangeType(obj, defaultValue.GetType());
}
catch
{
return defaultValue;
}
}
/// <summary>
/// 获取字符串类型数据
/// </summary>
/// <param name="dr"></param>
/// <param name="name"></param>
/// <returns></returns>
public static string GetString(this DataRow dr, string name)
{
if (dr[name] != DBNull.Value && dr[name] != null)
return dr[name].ToString();
return String.Empty;
}
/// <summary>
/// 获取非空类型数据
/// </summary>
/// <param name="con"></param>
/// <param name="name"></param>
/// <returns></returns>
public static DateTime GetDateTime(this DataRow dr, string name)
{
DateTime result = DateTime.Now;
if (dr[name] != DBNull.Value && dr[name] != null)
{
if (!DateTime.TryParse(dr[name].ToString(), out result))
throw new Exception("日期格式数据转换失败");
}
return result;
}
/// <summary>
/// 获取可空类型日期数据
/// </summary>
/// <param name="dr"></param>
/// <param name="name"></param>
/// <returns></returns>
public static DateTime? GetNullDateTime(this DataRow dr, string name)
{
DateTime? result = null;
DateTime time = DateTime.Now;
if (dr[name] != DBNull.Value && dr[name] != null)
{
if (!DateTime.TryParse(dr[name].ToString(), out time))
throw new Exception("日期格式数据转换失败");
result = time;
}
return result;
}
/// <summary>
/// 获取guid类型数据
/// </summary>
/// <param name="dr"></param>
/// <param name="name"></param>
/// <returns></returns>
public static Guid GetGuid(this DataRow dr, string name)
{
Guid guid = Guid.Empty;
if (dr[name] != DBNull.Value && dr[name] != null)
{
if (Guid.TryParse(dr[name].ToString(), out guid))
throw new Exception("guid类型数据转换失败");
}
return guid;
}
/// <summary>
/// 获取整形数据
/// </summary>
/// <param name="dr"></param>
/// <param name="name"></param>
/// <returns></returns>
public static int GetInt32(this DataRow dr, string name)
{
int result = 0;
if (dr[name] != DBNull.Value && dr[name] != null)
{
if (!int.TryParse(dr[name].ToString(), out result))
throw new Exception("整形转换失败");
}
return result;
}
/// <summary>
/// 获取双精度类型数据
/// </summary>
/// <param name="dr"></param>
/// <param name="name"></param>
/// <returns></returns>
public static double GetDouble(this DataRow dr, string name)
{
double result = 0.00;
if (dr[name] != DBNull.Value && dr[name] != null)
{
if (!double.TryParse(dr[name].ToString(), out result))
throw new Exception("双精度类型转换失败");
}
return result;
}
/// <summary>
/// 获取单精度类型数据
/// </summary>
/// <param name="dr"></param>
/// <param name="name"></param>
/// <returns></returns>
public static float GetSingle(this DataRow dr, string name)
{
float result = 0.00f;
if (dr[name] != DBNull.Value && dr[name] != null)
{
if (!float.TryParse(dr[name].ToString(), out result))
throw new Exception("单精度类型转换失败");
}
return result;
}
/// <summary>
/// 获取decimal类型数据
/// </summary>
/// <param name="dr"></param>
/// <param name="name"></param>
/// <returns></returns>
public static decimal GetDecimal(this DataRow dr, string name)
{
decimal result = 0.00m;
if (dr[name] != DBNull.Value && dr[name] != null)
{
if (!decimal.TryParse(dr[name].ToString(), out result))
throw new Exception("Decimal类型转换失败");
}
return result;
}
/// <summary>
/// 获取int16类型数据
/// </summary>
/// <param name="dr"></param>
/// <param name="name"></param>
/// <returns></returns>
public static Int16 GetInt16(this DataRow dr, string name)
{
short result = 0;
if (dr[name] != DBNull.Value && dr[name] != null)
{
if (!short.TryParse(dr[name].ToString(), out result))
throw new Exception("短整形转换失败");
}
return result;
}
/// <summary>
/// 获取Byte类型数据
/// </summary>
/// <param name="dr"></param>
/// <param name="name"></param>
/// <returns></returns>
public static byte GetByte(this DataRow dr, string name)
{
byte result = 0;
if (dr[name] != DBNull.Value && dr[name] != null)
{
if (!byte.TryParse(dr[name].ToString(), out result))
throw new Exception("Byte类型转换失败");
}
return result;
}
/// <summary>
/// 获取bool类型数据如果传值是1或者是返回true;
/// </summary>
/// <param name="con"></param>
/// <param name="name"></param>
/// <returns></returns>
public static bool GetBool(this DataRow dr, string name)
{
if (dr[name] != DBNull.Value && dr[name] != null)
{
return dr[name].ToString() == "1" || dr[name].ToString() == "是" || dr[name].ToString().ToLower() == "true";
}
return false;
}
#endregion
}
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