Question

我有一个breadcrumb表，我想返回最近插入的行。在SQL中，它将是MAX()函数，但不确定如何在LINQ中执行等效操作。基本上我想选择具有最高BreadCrumbID WHERE ProjectID = 49的行。

这是我现在的查询，它将选择所有行WHERE ProjectID = 49。我想选择BreadCrumbID最高的行。

谢谢！

代码：

using (dbPSREntities5 myEntities = new dbPSREntities5())
{
   var currentStatus = (from tbBreadCrumb in myEntities.tbBreadCrumbs.Where(x => x.ProjectID == 49)
                        select new
                        {
                           Status = tbBreadCrumb.BreadCrumbID,
                        });
}

Answer 1

试试这个：

using (dbPSREntities5 myEntities = new dbPSREntities5())
    {
        var currentStatus = (from tbBreadCrumb in myEntities.tbBreadCrumbs.Where(x => x.ProjectID == myEntities.tbBreadCrumbs.Max(b=>b.ProjectId))
                              select new
                              {
                                  Status = tbBreadCrumb.BreadCrumbID,
                              });

    }

Answer 2

尝试以下查询

var currentStatus = 
  from x in myEntities.tbBreadCrumbs
  where x.ProjectID == 49
  orderby x.BreadCrumbID desc
  select x.BreadCrumbID;

该查询的第一个结果将是BreadCrumbID值为ProjectID的最高值{{1}}

Answer 3

此查询应该为您提供最高的BreadCrumbId，其中ProjectID = 4

using (dbPSREntities5 myEntities = new dbPSREntities5())
{
    var highestId = myEntities.tbBreadCrumbs.Where(x => x.ProjectID == 49)
                                            .Max(x => x.BreadCrumbID);
}

Answer 4

您可以使用Max() linq扩展方法

var crum = myEntities.tbBreadCrumbs.Max(d=>d.breadcrumbId)

Answer 5

Var highestId = myEntities.breadcrumbs.lastOrDefault（x =＆gt; x.ProjectId == 49）

Answer 6

试试这个，如果ProjectID = 49中没有BreadCrumb它会给0或者给出max BreadCrumbID

using (dbPSREntities5 myEntities = new dbPSREntities5())
{
    var query=myEntities.tbBreadCrumbs.Where(x => x.ProjectID == 49);
    var highestId = query.Any() ? query.Max(x => x.BreadCrumbID) : 0;
}

C＃使用LINQ选择行的最大ID

6 个答案: