在使用DataRow讀取數據時，通常會遇到數據可能為Null, 但是又需要轉換為如int等其它類型的數據，因此就通常會寫這樣的代碼：

if (dr[name] != DBNull.Value && dr[name] != null)
{
??? if (!int.TryParse(dr[name].ToString(), out result))
??????? throw new Exception("整形轉換失敗");
}

而且這樣的代碼通常會大段大段出現在很多地方。
對于比較懶惰的程序員來說，這樣的RY(repeat yourself)是一件很痛苦的事情，因此是時候來想個更好的方法了。這里首先想到的就是Extension Method。

很簡單的幾句代碼，有了這個方法之后，在使用DataRow時，就可以通過擴展方法讀取數據了

model.Id =? dr.SafeRead<Int32>("Id",0);
model.codeNum = dr.GetString("codeNum");

簡單但是實用的代碼，希望對大家在項目中有所幫助。

這里參考了,一下兩篇文章，并進行了代碼重新組織，最后是整理后類源碼

使用 Extension Methods 來使 IDataReader 更加方便

C#底層SqlDataReader類常用擴展

public static class SystemDataExtension{#region DataReader 擴展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> /// 獲取字符串類型數據 /// </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> /// 獲取非空類型數據 /// </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("日期格式數據轉換失敗");}return result;}/// <summary> /// 獲取可空類型日期數據 /// </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("日期格式數據轉換失敗");result = time;}return result;}/// <summary> /// 獲取guid類型數據 /// </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類型數據轉換失敗");}return guid;}/// <summary> /// 獲取整形數據 /// </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("整形轉換失敗");}return result;}/// <summary> /// 獲取雙精度類型數據 /// </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("雙精度類型轉換失敗");}return result;}/// <summary> /// 獲取單精度類型數據 /// </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("單精度類型轉換失敗");}return result;}/// <summary> /// 獲取decimal類型數據 /// </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類型轉換失敗");}return result;}/// <summary> /// 獲取int16類型數據 /// </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("短整形轉換失敗");}return result;}/// <summary> /// 獲取Byte類型數據 /// </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類型轉換失敗");}return result;}/// <summary> /// 獲取bool類型數據如果傳值是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 擴展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> /// 獲取字符串類型數據 /// </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> /// 獲取非空類型數據 /// </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("日期格式數據轉換失敗");}return result;}/// <summary> /// 獲取可空類型日期數據 /// </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("日期格式數據轉換失敗");result = time;}return result;}/// <summary> /// 獲取guid類型數據 /// </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類型數據轉換失敗");}return guid;}/// <summary> /// 獲取整形數據 /// </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("整形轉換失敗");}return result;}/// <summary> /// 獲取雙精度類型數據 /// </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("雙精度類型轉換失敗");}return result;}/// <summary> /// 獲取單精度類型數據 /// </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("單精度類型轉換失敗");}return result;}/// <summary> /// 獲取decimal類型數據 /// </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類型轉換失敗");}return result;}/// <summary> /// 獲取int16類型數據 /// </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("短整形轉換失敗");}return result;}/// <summary> /// 獲取Byte類型數據 /// </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類型轉換失敗");}return result;}/// <summary> /// 獲取bool類型數據如果傳值是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}

　　

轉載于:https://www.cnblogs.com/IlidanStormRage/p/5737062.html

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