Question

我正在尝试在Linq中将此查询转换为（Microsoft）SQL。

SELECT        MAX(ID) AS MyValue
FROM            Table
WHERE    "list contains 1 or 2 or 3"

我该怎么做？我看到的唯一例子只是在整个列上产生最大值而不是每个组（例如TogetherId = 1的示例）

我想得到一个结果：行：

TogetherId | Id
1 | 1
1 | 2
1 | 16
2 | 7
3 | 8
3 | 9

结果：

TogetherId | Id
1 | 16
2 | 7
3 | 9

如何使用Linq执行此操作？

List<int> myList; // Consider the list to be populated.

我已经将这件作品用于Where - ＆gt; where myList.Contains(MyTable.ID)

我只想在C＃中为一个字符串列表选择1列。

Answer 1

这样的东西？

myList = yourList.GroupBy(x => x.TogetherId)
                 .Select(x => x.OrderByDescending(y => y.Id).First())
                 .ToList();

Answer 2

您会想要GroupBy后面跟Max：

 var newList = myList.GroupBy(x => x.TogetherId, x => x.Id)
            .Select(x => new {
                  TogetherId = x.Key,
                  MaxId = x.Max()
             })
            .ToList();

实例：http://rextester.com/LROWSF91311

Answer 3

list
.GroupBy(x => x.TogetherId)
.Select(g => new { TogetherId = g.Key, Max = g.Max(x => x.Id) });

Answer 4

和带有查询语法的变体

myList = (from x in yourList
         group x by x.TogetherId into g
         select new {
             TogetherId = g.Key, 
             Max = g.Max(a=>a.Id)
         }).ToList()

Answer 5

List<int> myList = new List<int>();
myList.Add(1);
myList.Add(2);

List<String> myList1 = MyTable.Where(x=> myList.Contains(x.TogetherId)).GroupBy(x => x.TogetherId)
                            .Select(x => Convert.ToString(x.OrderByDescending(y => y.Id).First().Id))
                            .ToList();

List <int>：每个项目的Linq获取列表</int>

5 个答案: