動態填寫實體類的值

/// <summary>
    /// 動態填寫實體類的值
    /// </summary>
    /// <typeparam name="T"></typeparam>
    public class DynamicEntityBuilder<T>
    {
        private static readonly MethodInfo getValueMethod = typeof(IDataRecord).GetMethod("get_Item", new Type[] { typeof(int) });
        private static readonly MethodInfo isDBNullMethod = typeof(IDataRecord).GetMethod("IsDBNull", new Type[] { typeof(int) });
        private delegate T Load(IDataRecord dataRecord);
        private Load handler;

        private DynamicEntityBuilder() { }

        public T Build(IDataRecord dataRecord)
        {
            return handler(dataRecord);
        }

        public static DynamicEntityBuilder<T> CreateBuilder(IDataRecord dataRecord)
        {
            DynamicEntityBuilder<T> dynamicBuilder = new DynamicEntityBuilder<T>();

            DynamicMethod method = new DynamicMethod("DynamicCreate", typeof(T), new Type[] { typeof(IDataRecord) }, 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 < dataRecord.FieldCount; i++)
            {
                PropertyInfo propertyInfo = typeof(T).GetProperty(dataRecord.GetName(i));
                Label endIfLabel = generator.DefineLabel();

                if (propertyInfo != null && propertyInfo.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, dataRecord.GetFieldType(i));
                    generator.Emit(OpCodes.Callvirt, propertyInfo.GetSetMethod());

                    generator.MarkLabel(endIfLabel);
                }
            }

            generator.Emit(OpCodes.Ldloc, result);
            generator.Emit(OpCodes.Ret);

            dynamicBuilder.handler = (Load)method.CreateDelegate(typeof(Load));
            return dynamicBuilder;
        }
    }

使用

 public ERole Select(int roleID)
        {
            ERole entity = new ERole();
            string sql = string.Format("select * from Role with(nolock) where roleid = {0}",roleID);
            DbCommand cmd = Db.EsfCrmReader.GetSqlStringCommand(sql);         
          
            using (IDataReader dataReader = Db.EsfCrmReader.ExecuteReader(cmd))
            {
                if (dataReader.Read())
                {  
                    entity = DynamicEntityBuilder<ERole>.CreateBuilder(dataReader).Build(dataReader);  
                }
            }
            return entity;
        }