- 修复 GroupBy 类型转换错误；#186

- 修复 .ToList(a => new DTO(a.id)) 报 未将对象引用设置到对象的实例 问题； #187
- 修复 update语句，二元运算解析出错； #184

FreeSql/Interface/Curd/ISelect/ISelectGrouping.cs

@@ -127,14 +127,14 @@ namespace FreeSql
         /// <typeparam name="T3"></typeparam>
         /// <param name="column"></param>
         /// <returns></returns>
-        T3 Sum<T3>(T3 column);
+        decimal Sum<T3>(T3 column);
         /// <summary>
         /// 平均值
         /// </summary>
         /// <typeparam name="T3"></typeparam>
         /// <param name="column"></param>
         /// <returns></returns>
-        T3 Avg<T3>(T3 column);
+        decimal Avg<T3>(T3 column);
         /// <summary>
         /// 最大值
         /// </summary>