如何从linq中的select new子句中选择记录

Question

我有以下代码，我有3个表，分别是Department，DepartmentTask和DepartmentPosition。 这是表格：

public partial class Department()
{
   public int DepartmentId { get; set; }
   public string DepartmentName { get; set; }
   public Nullable<int> ParentDepartmentId { get; set; }    
}
public partial class DepartmentPosition
{
    public int PositionId { get; set; }
    public int DepartmentId { get; set; }
    public string PositiontName { get; set; }        
}
public partial class DepartmentTask
{
    public int TaskId { get; set; }
    public int DepartmentId { get; set; }
    public string TaskName { get; set; }       
}

因此，任何部门都可以成为另一个部门（任务和职位）的父级。 因此，在这里我想根据DepartmentId从表中选择所有记录，这些记录是特定部门的子级。

var z = from n in dbbs.Department
        select new
        {
            deptcount = dbbs.Department.Count(p => p.ParentDepartmentId == id),
            poscount = dbbs.DepartmentPosition.Count(x => x.DepartmentId == id),
            taskcount = dbbs.DepartmentTask.Count(t => t.DepartmentId == id)
        };
if(z.Count()>0)
{ 
//do something
}
else
{

}

现在，如果表中没有记录，它仍在if块中。 我想知道如何限制是否没有根据查询的记录。

Answer 1

我不确定您要使用select语句尝试实现什么。 你不能使用：

var deptcount = dbbs.Department.Count(p => p.ParentDepartmentId == id);
var poscount = dbbs.DepartmentPosition.Count(x => x.DepartmentId == id);
var taskcount = dbbs.DepartmentPosition.Count(t => t.DepartmentId == id);

if(deptcount > 0) 
{
 //do something
}

如果您尝试根据部门进行分组，请解释，我将更新答案。

Answer 2

var count= from s in ObjectContext.tb1
                              join c in ObjectContext.tb2 on s.ParentCategoryID equals c.PersonCategoryID
                              join p in ObjectContext.tb3 on c.BusinessEntityID equals p.BusinessEntityID
                              select new count()
                              {
                                 tbl1count =c.count()
                                 tbl2count =p.count()
                                 tbl3count =p.count()
                              };

然后

if(count.tbl1count.any()){
//do whatever you need}