using System;
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using System.Collections.Generic;
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using System.Data;
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using System.Linq;
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using System.Web;
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namespace VueWebApi.Util
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{
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/// <summary>
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/// 值转换器
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/// </summary>
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/// <typeparam name="T">指定值的类型</typeparam>
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/// <param name="obj">取值来源</param>
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/// <returns>返回指定类型的值</returns>
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[Serializable]
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public delegate T ObjectValueParser<out T>(object obj);
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/// <summary>
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/// 尝试将值转换成指定类型 返回转换结果
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/// </summary>
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/// <typeparam name="T">指定值的类型</typeparam>
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/// <param name="obj">取值来源</param>
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/// <param name="valueOutput">若转换成功 则out转换结果 否则 out默认T类型值</param>
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/// <returns></returns>
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public delegate bool ObjectValueTryParser<T>(object obj, out T valueOutput);
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/// <summary>
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/// 尝试将值转换成指定类型 返回转换结果
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/// </summary>
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/// <typeparam name="T">指定值的类型</typeparam>
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/// <param name="str">取值来源字符串</param>
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/// <returns>返回指定类型的值</returns>
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[Serializable]
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public delegate T StringValueParser<out T>(string str);
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/// <summary>
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/// 尝试将值转换成指定类型 返回转换成功与否
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/// </summary>
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/// <typeparam name="T">指定值的类型</typeparam>
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/// <param name="str">取值来源字符串</param>
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/// <param name="valueOutput">若转换成功 则out转换结果 否则 out默认T类型值</param>
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/// <returns></returns>
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[Serializable]
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public delegate bool StringValueTryParser<T>(string str, out T valueOutput);
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/// <summary>
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/// 实体帮助类
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/// </summary>
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public class EntityHelper
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{
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/// <summary>
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/// 从一行数据中尝试获取指定列名的值
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/// </summary>
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/// <param name="dr">源数据行</param>
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/// <param name="columnName">指定列名</param>
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/// <returns>若指定的列名存在并有效则返回取到的对象，若指定列名不存在或者为无效数据则返回null</returns>
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public static object GetObject(DataRow dr, string columnName)
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{
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if (dr != null && dr.Table.Columns.Contains(columnName) && dr[columnName] != null && dr[columnName] != DBNull.Value)
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return dr[columnName];
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return null;
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}
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/// <summary>
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/// 从一行数据中尝试获取指定引用类型的值
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/// </summary>
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/// <typeparam name="T">指定类型的值</typeparam>
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/// <param name="dr">源数据行</param>
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/// <param name="columnName">列名</param>
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/// <param name="defVal">列无效时返回的默认值</param>
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/// <param name="parser">值转换器 若给定的值转换器为null，则使用as强制转换，若as转换为null 则返回默认值</param>
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/// <returns></returns>
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public static T GetT<T>(DataRow dr, string columnName, T defVal, ObjectValueParser<T> parser = null) where T : class
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{
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var obj = GetObject(dr, columnName);
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return Get(obj, defVal, parser);
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}
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/// <summary>
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/// 将对象转换为指定类型数据 转换失败返回设置的默认值
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/// </summary>
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/// <typeparam name="T">指定的类型</typeparam>
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/// <param name="source">数据源</param>
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/// <param name="defVal">列无效时返回的默认值</param>
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/// <param name="parser">值转换器 若给定的值转换器为null，则使用as强制转换，若as转换为null 则返回默认值</param>
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/// <returns></returns>
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public static T Get<T>(object source, T defVal, ObjectValueParser<T> parser = null) where T : class
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{
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if (source == null) return defVal;
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if (parser != null)
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{
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return parser(source);
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}
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return source as T ?? defVal;
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}
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/// <summary>
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/// 从一行数据中尝试获取指定引用类型的值
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/// </summary>
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/// <typeparam name="T">指定的类型</typeparam>
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/// <param name="dr">源数据行</param>
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/// <param name="columnName">列名</param>
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/// <param name="defVal">列无效时返回的默认值</param>
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/// <param name="parser">值转换器 若给定的值转换器为null，则使用as强制转换，若as转换为null 则返回默认值</param>
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/// <returns></returns>
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public static T TryGetT<T>(DataRow dr, string columnName, T defVal, ObjectValueTryParser<T> parser = null) where T : class
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{
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var obj = GetObject(dr, columnName);
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return TryGetT(obj, defVal, parser);
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}
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/// <summary>
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/// 将对象尝试转换为指定类型的数据 转换失败返回指定的默认值
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/// </summary>
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/// <typeparam name="T">指定的类型</typeparam>
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/// <param name="source">数据源</param>
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/// <param name="defVal">默认值</param>
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/// <param name="parser">值转换器 若给定的值转换器为null，则使用as强制转换，若as转换为null 则返回默认值</param>
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/// <returns></returns>
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public static T TryGetT<T>(object source, T defVal, ObjectValueTryParser<T> parser = null) where T : class
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{
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if (source == null) return defVal;
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if (parser == null) return source as T ?? defVal;
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T temp;
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if (parser(source, out temp))
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{
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return temp;
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}
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return source as T ?? defVal;
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}
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/// <summary>
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/// 从一行数据中尝试获取指定值类型的值
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/// </summary>
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/// <typeparam name="T">指定类型的值</typeparam>
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/// <param name="dr">源数据行</param>
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/// <param name="columnName">列名</param>
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/// <param name="defVal">列无效时返回的默认值</param>
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/// <param name="parser">值转换器</param>
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/// <returns></returns>
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public static T GetT<T>(DataRow dr, string columnName, T defVal, StringValueParser<T> parser) where T : struct
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{
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var obj = GetObject(dr, columnName);
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return GetT(obj, defVal, parser);
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}
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/// <summary>
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/// 将对象转换为指定类型数据 转换失败返回设置的默认值
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/// </summary>
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/// <typeparam name="T">指定的类型</typeparam>
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/// <param name="source">数据源</param>
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/// <param name="defVal">列无效时返回的默认值</param>
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/// <param name="parser">值转换器</param>
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/// <returns></returns>
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public static T GetT<T>(object source, T defVal, StringValueParser<T> parser) where T : struct
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{
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return source != null ? parser(source.ToString()) : defVal;
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}
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/// <summary>
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/// 从一行数据中尝试获取指定值类型的值
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/// </summary>
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/// <typeparam name="T">指定类型的值</typeparam>
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/// <param name="dr">源数据行</param>
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/// <param name="columnName">列名</param>
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/// <param name="defVal">列无效时返回的默认值</param>
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/// <param name="parser">值转换器</param>
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/// <returns></returns>
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public static T TryGetT<T>(DataRow dr, string columnName, T defVal, StringValueTryParser<T> parser) where T : struct
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{
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var obj = GetObject(dr, columnName);
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return TryGetT(obj, defVal, parser);
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}
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/// <summary>
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/// 将对象尝试转换为指定类型的数据 转换失败返回指定的默认值
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/// </summary>
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/// <typeparam name="T">指定的类型</typeparam>
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/// <param name="obj">数据源</param>
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/// <param name="defVal">默认值</param>
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/// <param name="parser">值转换器</param>
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/// <returns></returns>
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public static T TryGetT<T>(object obj, T defVal, StringValueTryParser<T> parser) where T : struct
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{
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if (obj != null)
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{
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T val;
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if (parser(obj.ToString(), out val))
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{
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return val;
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}
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}
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return defVal;
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}
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/// <summary>
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/// 从一行数据中尝试获取字符串
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/// </summary>
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/// <param name="dr">源数据行</param>
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/// <param name="columnName">列名</param>
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/// <param name="defVal">列无效时返回的默认值</param>
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/// <returns></returns>
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public static string GetString(DataRow dr, string columnName, string defVal)
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{
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var obj = GetObject(dr, columnName);
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return obj != null ? obj.ToString() : defVal;
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}
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/// <summary>
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/// 获取字符串 检测 数据源为空时返回默认值
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/// </summary>
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/// <param name="source">数据源</param>
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/// <param name="defVal">默认值</param>
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/// <returns></returns>
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public static string GetString(object source, string defVal)
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{
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if (source != null)
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{
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return source as string ?? source.ToString();
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}
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return defVal;
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}
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/// <summary>
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/// 从一行数据中尝试获取整数
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/// </summary>
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/// <param name="dr">源数据行</param>
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/// <param name="columnName">列名</param>
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/// <param name="defVal">列无效时返回的默认值</param>
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/// <returns></returns>
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public static int GetInt(DataRow dr, string columnName, int defVal)
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{
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return TryGetT(dr, columnName, defVal, int.TryParse);
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}
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/// <summary>
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/// 从数据员获取整数
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/// </summary>
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/// <param name="source">数据源</param>
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/// <param name="defVal">获取失败时的默认值</param>
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/// <returns></returns>
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public static int GetInt(object source, int defVal)
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{
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return TryGetT(source, defVal, int.TryParse);
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}
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/// <summary>
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/// 从一行数据中尝试获取日期
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/// </summary>
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/// <param name="dr">源数据行</param>
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/// <param name="columnName">列名</param>
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/// <param name="defVal">列无效时返回的默认值</param>
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/// <returns></returns>
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public static DateTime GetDateTime(DataRow dr, string columnName, DateTime defVal)
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{
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return TryGetT(dr, columnName, defVal, DateTime.TryParse);
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}
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/// <summary>
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/// 从数据源中 获取日期
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/// </summary>
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/// <param name="source">数据源</param>
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/// <param name="defVal">获取失败时的默认值</param>
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/// <returns></returns>
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public static DateTime GetDateTime(object source, DateTime defVal)
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{
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return TryGetT(source, defVal, DateTime.TryParse);
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}
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}
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}
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