group by和count使用linqgroup by和count是用于数据查询和统计的两个常用操作。 group by:group by是一种数据分组的操作,它将数据集按照指定的字段进行分组,将具有相同字段值的数据归为一组。在LINQ中,可以使用group by关键字来实现该操作。 例如,假设有一个学生表,包含学生的姓名和所属班级字段。我们可以使用group...
下面是一个示例代码,演示了如何使用LINQ的Group By操作进行字符串和count分组属性的子属性: 代码语言:txt 复制 // 假设有一个Person类,包含Name和Age属性 class Person { public string Name { get; set; } public int Age { get; set; } } // 假设有一个Person集合 List<Person> persons = ...
ActivityLocation=groupActivity.Key.ActivityLocation, Description=groupActivity.Key.Description, CreateOn=groupActivity.Key.CreateOn, CreateBy=groupActivity.Key.CreateBy, LastModifyBy=groupActivity.Key.LastModifyBy, LastModifyOn=groupActivity.Key.LastModifyOn, RegisteredCount= groupActivity.Count(g=>g.fkAc...
group p by p.CategoryID into g select new { g.Key, NumProducts = g.Count(p =>p.Discontinued) }; 语句描述:Linq使用Group By和Count得到每个CategoryID中断货产品的数量。 说明:先按CategoryID归类,取出CategoryID值和各个分类产品的断货数量。 Count函数里,使用了Lambda表达式,Lambda表达式中的p,代表这个...
group ps by ps.Name into g select new { name = g.Key, count = g.Count(), ageC = g.Sum(item => item.Age), moneyC = g.Sum(item => item.Money) }; dataGridView1.DataSource = ls.ToList(); //dataGridView1.DataSource = ls2.ToList(); ...
3、分组并对各组进行数值计算 来看一个SQL中常用的场景例子: /* SQL里的表达: 按照用户职业分组,查出每个分组的人数及各组的年龄最大值、最小值、平均值和总和 */SELECToccupation,COUNT(id
SELECT p.ParentId, COUNT(c.ChildId) FROM ParentTable p LEFT OUTER JOIN ChildTable c ON p.ParentId = c.ChildParentId GROUP BY p.ParentId How can I translate this into LINQ to SQL? I got stuck at the COUNT(c.ChildId), the generated SQL always seems to output COUNT(*). Here's ...
GROUP BY Category.CategoryID I'm trying to write a LINQ query to do the same. What should I Group By and where do I call the Count function in LINQ query? thanks All replies (1) Monday, November 3, 2008 2:33 PM ✅Answered ...
用自定义对象类ListGroupResult替代 IGrouping<string, User>classListGroupResult{publicstringKey{get;set;}publicList<User>UserList{get;set;}}IIEnumerable<ListGroupResult>UserGroupByOccupation=fromuinlistgroupubyu.occupationintonselectnewListGroupResult(){Key=n.Key,//这个Key是occupationUserList=n.ToList...
Thanks for the response. You cleared up the "Use Lina for Everything" debate for me. I have many perfectly functional sprocs that I would be happy reusing. I'm running into problems with how to get the models set up correctly, especially when it involves derived columns such as count....