using System;

 using System.Collections.Generic;

 using System.Data;

 using System.Data.Common;

 using System.Data.SqlClient;

 using System.Linq;

 using System.Linq.Expressions;

 using System.Reflection;

 using System.Text;

 using System.Threading.Tasks;

 namespace Demo1

 {

     public static class EntityConverter

     {

         #region

         /// <summary>

         /// DataTable生成实体

         /// </summary>

         /// <typeparam name="T"></typeparam>

         /// <param name="dataTable"></param>

         /// <returns></returns>

         public static List<T> ToList<T>(this DataTable dataTable) where T : class, new()

         {

             if (dataTable == null || dataTable.Rows.Count <= ) throw new ArgumentNullException("dataTable", "当前对象为null无法生成表达式树");

             Func<DataRow, T> func = dataTable.Rows[].ToExpression<T>();

             List<T> collection = new List<T>(dataTable.Rows.Count);

             foreach (DataRow dr in dataTable.Rows)

             {

                 collection.Add(func(dr));

             }

             return collection;

         }

         /// <summary>

         /// 生成表达式

         /// </summary>

         /// <typeparam name="T"></typeparam>

         /// <param name="dataRow"></param>

         /// <returns></returns>

         public static Func<DataRow, T> ToExpression<T>(this DataRow dataRow) where T : class, new()

         {

             if (dataRow == null) throw new ArgumentNullException("dataRow", "当前对象为null 无法转换成实体");

             ParameterExpression parameter = Expression.Parameter(typeof(DataRow), "dr");

             List<MemberBinding> binds = new List<MemberBinding>();

             for (int i = ; i < dataRow.ItemArray.Length; i++)

             {

                 String colName = dataRow.Table.Columns[i].ColumnName;

                 PropertyInfo pInfo = typeof(T).GetProperty(colName);

                 if (pInfo == null || !pInfo.CanWrite) continue;

                 MethodInfo mInfo = typeof(DataRowExtensions).GetMethod("Field", new Type[] { typeof(DataRow), typeof(String) }).MakeGenericMethod(pInfo.PropertyType);

                 MethodCallExpression call = Expression.Call(mInfo, parameter, Expression.Constant(colName, typeof(String)));

                 MemberAssignment bind = Expression.Bind(pInfo, call);

                 binds.Add(bind);

             }

             MemberInitExpression init = Expression.MemberInit(Expression.New(typeof(T)), binds.ToArray());

             return Expression.Lambda<Func<DataRow, T>>(init, parameter).Compile();

         }

         #endregion

         /// <summary>

         /// 生成lambda表达式

         /// </summary>

         /// <typeparam name="T"></typeparam>

         /// <param name="reader"></param>

         /// <returns></returns>

         public static Func<SqlDataReader, T> ToExpression<T>(this SqlDataReader reader) where T : class, new()

         {

             if (reader == null || reader.IsClosed || !reader.HasRows) throw new ArgumentException("reader", "当前对象无效");

             ParameterExpression parameter = Expression.Parameter(typeof(SqlDataReader), "reader");

             List<MemberBinding> binds = new List<MemberBinding>();

             for (int i = ; i < reader.FieldCount; i++)

             {

                 String colName = reader.GetName(i);

                 PropertyInfo pInfo = typeof(T).GetProperty(colName);

                 if (pInfo == null || !pInfo.CanWrite) continue;

                 MethodInfo mInfo = reader.GetType().GetMethod("GetFieldValue").MakeGenericMethod(pInfo.PropertyType);

                 MethodCallExpression call = Expression.Call(parameter, mInfo, Expression.Constant(i));

                 MemberAssignment bind = Expression.Bind(pInfo, call);

                 binds.Add(bind);

             }

             MemberInitExpression init = Expression.MemberInit(Expression.New(typeof(T)), binds.ToArray());

             return Expression.Lambda<Func<SqlDataReader, T>>(init, parameter).Compile();

         }

     }

 }

 using System;

 using System.Collections.Generic;

 using System.Data;

 using System.Data.Common;

 using System.Data.SqlClient;

 using System.Diagnostics;

 using System.Linq;

 using System.Reflection;

 using System.Text;

 using System.Threading.Tasks;

 namespace Demo1

 {

     class Program

     {

         static void Main(string[] args)

         {

             String conString = "Data Source=.; Initial Catalog=master; Integrated Security=true;";

             Func<SqlDataReader, Usr> func = null;

             List<Usr> usrs = new List<Usr>();

             using (SqlDataReader reader = GetReader(conString, "select object_id 'ID',name 'Name' from sys.objects", CommandType.Text, null))

             {

                 while (reader.Read())

                 {

                     if (func == null)

                     {

                         func = reader.ToExpression<Usr>();

                     }

                     Usr usr = func(reader);

                     usrs.Add(usr);

                 }

             }

             usrs.Clear();

             Console.ReadKey();

         }

         public static SqlDataReader GetReader(String conString, String sql, CommandType type, params SqlParameter[] pms)

         {

             SqlConnection conn = new SqlConnection(conString);

             SqlCommand cmd = new SqlCommand(sql, conn);

             cmd.CommandType = type;

             if (pms != null && pms.Count() > )

             {

                 cmd.Parameters.AddRange(pms);

             }

             conn.Open();

             return cmd.ExecuteReader(CommandBehavior.CloseConnection);

         }

     }

     class Usr

     {

         public Int32 ID { get; set; }

         public String Name { get; set; }

     }

 }