C# 把DT 的数据转换成 list<Model> EntityByEmit

using System;
using System.Collections.Generic;
using System.Text;
using System.Reflection.Emit;
using System.Reflection;
using System.Data;

namespace Common
{
    /// <summary>
    /// EntityByEmit

/// </summary>
    public static class ToEntityByEmit
    {
        public static List<T> GetList<T>(DataTable dt)
        {
            List<T> lst = new List<T>();
            if (dt == null) return lst;
            DataTableEntityBuilder<T> eblist = DataTableEntityBuilder<T>.CreateBuilder(dt.Rows[0]);
            foreach (DataRow dr in dt.Rows)
            {
                lst.Add(eblist.Build(dr));
            }
            dt.Dispose();
            dt = null;
            return lst;
        }
    }

    public class DataTableEntityBuilder<T>
    {
        private static readonly MethodInfo getValueMethod = typeof(DataRow).GetMethod("get_Item", new Type[] { typeof(int) });
        private static readonly MethodInfo isDBNullMethod = typeof(DataRow).GetMethod("IsNull", new Type[] { typeof(int) });
        private delegate T Load(DataRow dr);

        private Load handler;
        private DataTableEntityBuilder() { }

        public T Build(DataRow dr)
        {
            return handler(dr);
        }

        public static DataTableEntityBuilder<T> CreateBuilder(DataRow dr)
        {
            DataTableEntityBuilder<T> dynamicBuilder = new DataTableEntityBuilder<T>();
            DynamicMethod method = new DynamicMethod("DynamicCreateEntity", typeof(T), new Type[] { typeof(DataRow) }, typeof(T), true);
            ILGenerator generator = method.GetILGenerator();
            LocalBuilder result = generator.DeclareLocal(typeof(T));
            generator.Emit(OpCodes.Newobj, typeof(T).GetConstructor(Type.EmptyTypes));
            generator.Emit(OpCodes.Stloc, result);

            for (int i = 0; i < dr.ItemArray.Length; i++)
            {
                PropertyInfo pi = typeof(T).GetProperty(dr.Table.Columns[i].ColumnName);
                Label endIfLabel = generator.DefineLabel();
                if (pi != null && pi.GetSetMethod() != null)
                {
                    generator.Emit(OpCodes.Ldarg_0);
                    generator.Emit(OpCodes.Ldc_I4, i);
                    generator.Emit(OpCodes.Callvirt, isDBNullMethod);
                    generator.Emit(OpCodes.Brtrue, endIfLabel);
                    generator.Emit(OpCodes.Ldloc, result);
                    generator.Emit(OpCodes.Ldarg_0);
                    generator.Emit(OpCodes.Ldc_I4, i);
                    generator.Emit(OpCodes.Callvirt, getValueMethod);
                    generator.Emit(OpCodes.Unbox_Any, pi.PropertyType);
                    generator.Emit(OpCodes.Callvirt, pi.GetSetMethod());
                    generator.MarkLabel(endIfLabel);
                }
            }
            generator.Emit(OpCodes.Ldloc, result);
            generator.Emit(OpCodes.Ret);
            dynamicBuilder.handler = (Load)method.CreateDelegate(typeof(Load));
            return dynamicBuilder;
        }
    }
}