有没有一种很好的方法来检测Linq-To-Entities查询中的空结果？

Question

我知道的唯一途径是尴尬：

'check for empty return 
Dim count As Integer = (From s In myEntity.employee Where employeeID = myEmployeeIDVariable).Count 

'If there is a record, then process 
If count > 0 Then 
    Dim r = (From s In myEntity.employee Where employeeID = myEmployeeIDVariable).First() 

    . . . do stuff . . . 
End If 

Answer 1

您可以将LINQ结果分配给一个变量，并检查.Count（）是否> 0。这样您就不需要执行两次相同的查询。

代码：

'check for empty return 
Dim r = (From s In myEntity.employee Where employeeID = myEmployeeIDVariable) 

'If there is a record, then process 
If r.Count() > 0 Then 
    . . . do stuff . . . 
End If 

Answer 2

使用.FirstOrDefault（）。如果有第一条记录，您将获得第一条记录;如果没有返回记录，则返回null。