背景介绍

C#中实体类的操作十分简便，一般情况下不需要涉及ADO.NET，如果需要将实体类转化为Datatable，这个时候就需要手动写一个方法了，代码如下图所示：

    public static class IEnumerableExtention{/// <summary>/// 将实体类转化为Datatable/// </summary>/// <typeparam name="T">实体类类型</typeparam>/// <param name="_ienu">实体对象</param>/// <param name="_tableName">表名</param>/// <returns>转化成的DataTable</returns>public static DataTable ToDataTable<T>(this IEnumerable<T> _ienu, string _tableName = "tableFromList") where T : new(){DataTable resultTable = new DataTable(_tableName);var pi = typeof(T).GetProperties(BindingFlags.Public|BindingFlags.Instance|BindingFlags.DeclaredOnly).ToList();if (_ienu == null || pi == null || pi.Count == 0){//当实体类为空的时候返回空的DataTable}else{pi.ForEach(p => { resultTable.Columns.Add(p.Name, p.PropertyType); });//生成Datatable列及列属性foreach (var _ie in _ienu){var dr = resultTable.NewRow();foreach (var prop in pi){if (prop.GetMethod != null){dr.SetField(prop.Name, prop.GetValue(_ie));}}resultTable.Rows.Add(dr);}}return resultTable;}/// <summary>/// 将实体类转化为DataSet/// </summary>/// <typeparam name="T">实体类类型</typeparam>/// <param name="_ienu"><实体对象/param>/// <param name="_tableName">表名</param>/// <returns>转化成的DataSet</returns>public static DataSet ToDataSet<T>(this IEnumerable<T> _ienu, string _tableName = "tableFromList") where T : new(){DataSet ds = new DataSet();ds.Tables.Add(_ienu.ToDataTable(_tableName));return ds;}/// <summary>/// 将实体类的对象列表复制给另一个类型相同的实体类/// </summary>/// <typeparam name="T">源实体类对象类型</typeparam>/// <param name="_ienu">源实体类</param>/// <returns>返回的实体类</returns>public static IEnumerable<T> Copy<T>(this IEnumerable<T> _ienu) where T : new(){var resultLists = new List<T>();var pi = typeof(T).GetProperties(BindingFlags.Instance|BindingFlags.Public|BindingFlags.DeclaredOnly).ToList();if (null == _ienu || null == pi || pi.Count == 0){//源实体类对象为空则返回空实体类}else{foreach (var _ie in _ienu){var resultList = new T();foreach (var prop in pi){if (prop.SetMethod != null && prop.GetMethod != null && !prop.PropertyType.IsAbstract){prop.SetValue(resultList,prop.GetValue(_ie));}}resultLists.Add(resultList);}}return resultLists;}/// <summary>/// 将一个实体类对象列表复制给另一个类型相同的实体类，支持筛选/// </summary>/// <typeparam name="T">源实体类对象类型</typeparam>/// <param name="_ienu">源实体类</param>/// <param name="_predicate">筛选的委托</param>/// <returns></returns>public static IEnumerable<T> Copy<T>(this IEnumerable<T> _ienu, Func<T, bool> _predicate = null) where T:new(){var resultLists = new List<T>();var pi = typeof(T).GetProperties(BindingFlags.Instance | BindingFlags.Public | BindingFlags.DeclaredOnly).ToList();if (null == _ienu || null == pi || pi.Count == 0){//源实体类对象为空则返回空实体类}else{if (_predicate != null){_ienu = _ienu.Where(_predicate);}else{foreach (var _ie in _ienu){var resultList = new T();foreach (var prop in pi){if (prop.SetMethod != null && prop.GetMethod != null && !prop.PropertyType.IsAbstract){prop.SetValue(resultList, prop.GetValue(_ie));}}resultLists.Add(resultList);}}}return resultLists;}/// <summary>/// 将一个实体类对象列表复制给另一个类型不相同的实体类,支持筛选，只复制名称和类型都相同的属性/// </summary>/// <typeparam name="TSource">源实体类类型</typeparam>/// <typeparam name="TResult">目标实体类类型</typeparam>/// <param name="_ienu">源实体类</param>/// <param name="_predicate">筛选的委托</param>/// <returns>返回的实体类</returns>public static List<TResult> CopyTo<TSource, TResult>(this IEnumerable<TSource> _ienu, Func<TSource, bool> _predicate = null) where TResult : new(){var resultLists = new List<TResult>();if (_ienu == null){throw new ArgumentNullException(nameof(_ienu));}var piSource = typeof(TSource).GetProperties(BindingFlags.Instance | BindingFlags.Public | BindingFlags.DeclaredOnly).ToList();//获取来源实体类属性var piResult = typeof(TResult).GetProperties(BindingFlags.Instance | BindingFlags.Public | BindingFlags.DeclaredOnly).ToList();//获取返回实体类属性if (piSource == null || piSource.Count == 0 || piResult == null || piResult.Count == 0){//返回空实体类return resultLists;}if (null != _predicate){_ienu = _ienu.Where(_predicate);}if (_ienu.Count() > 0)//判断来源实体类中列表数量{List<Tuple<PropertyInfo, bool>> PropLists = new List<Tuple<PropertyInfo, bool>>();piResult.ForEach(p =>{if (piSource.Exists(q => q.Name.Equals(p.Name))){PropLists.Add(Tuple.Create(p, p.PropertyType.Equals(piResult.FirstOrDefault(q => q.Name.Equals(p.Name)).PropertyType)));}});foreach (var _ie in _ienu){var resultList = new TResult();var samePropLists = PropLists.Where(p => p.Item2 == true).ToList();//提取类型也相同的属性foreach (var prop in samePropLists){if (prop.Item1.GetMethod != null && _ie.GetType().GetProperty(prop.Item1.Name).SetMethod != null){var value = piSource.FirstOrDefault(p => p.Name.Equals(prop.Item1.Name)).GetValue(_ie);prop.Item1.SetValue(resultList, value);}}resultLists.Add(resultList);}}return resultLists;}}

IEnumerableExtention类中包含五个方法：第一个直接将实体类转化为Datatable，第二个是在第一个的基础上包了一层DataSet并返回。第三个和第四个是将实体类列表复制给类型相同的另一个实体类，第四个支持筛选。第五个是将实体类复制给类型不相同的实体类，但是只支持复制类型和名字都相同的属性。