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：