Question

我有一个函数，并且希望能够使用参数更改相等性检查，以便对于一个版本，我提取所有等于x的项，而对于另一个版本，所有不等于x的项。

这是我的功能：

Public Function GetAllItemsByUserName(ByVal userName As String) As List(Of MyRecords)
    Dim itemsQuery = From myRecord as MyRecord from _ListOfRecords
                     Where myRecord.Name = userName
                     Select myRecord
    Return itemsQuery.ToList
End Function

所以我想只使用一个参数来翻转相等，这样我就可以提取所有= username的记录，或者所有那些！= username。有没有办法在不编写函数的两个版本的情况下这样做？

Answer 1

使用Xor（Exclusive Or）运算符。

Public Function GetAllItemsByUserName(ByVal userName As String, ByVal exclude As Boolean) As List(Of MyRecords)
    Dim itemsQuery = From myRecord as MyRecord from _ListOfRecords
                     Where (myRecord.Name = userName) Xor exclude
                     Select myRecord
    Return itemsQuery.ToList
End Function

Answer 2

试试这个：

Public Function GetAllItemsByUserName(ByVal userName As String, ByVal equal as Boolean) As List(Of MyRecords)
    Dim itemsQuery = From myRecord as MyRecord from _ListOfRecords
                     Where (myRecord.Name = userName) = equal
                     Select myRecord
    Return itemsQuery.ToList
End Function

Answer 3

您还可以使用Where中的If(conditional) operator：

Public Function GetAllItemsByUserName(ByVal userName As String, equals As Boolean) As List(Of MyRecords)
    Dim itemsQuery = 
        From myRecord In _ListOfRecords
        Where If(equals, myRecord.Name = userName, myRecord.Name <> userName)
        Select myRecord
    Return itemsQuery.ToList
End Function

Answer 4

这可以实现另一种方式：

Public Function GetAllItemsByUserName(ByVal userName As String, equals As Boolean) As List(Of MyRecords)
    Dim itemsQuery = From myRecord as MyRecord from _ListOfRecords
                     Where (equals && myRecord.Name = userName) Or (!equals && myRecord.Name != userName)
                     Select myRecord
    Return itemsQuery.ToList
End Function

如何翻转或反转相等检查

4 个答案: