使用Lambda 左连接查询DataTable

使用Lambda 查询DataTable,左连接

var query = dtWork.AsEnumerable().
                    GroupJoin(dtData.AsEnumerable(), 
                              w => w.Field<decimal>("ID"), d => d.Field<decimal>("ID"),
                             (w, d) => d.DefaultIfEmpty().
                                       Select(o =>new {
                                        INFO = o == null ? "" : o.Field<string>("APPROVED_INFO"),
                                        USER_NAME = w.Field<string>("USER_NAME")
                    })).SelectMany(o=>o);

不加SelectMany,效果如下：

加上SelectMany,效果如下：