[英]vb.net list<T> if not exist add
我有一個清單
Public Class Connoisseur
Public Name As String
Public Pieces As String
End Class
Private Sub Button26_Click(sender As Object, e As RibbonControlEventArgs) Handles Button26.Click
Dim CS As New List(Of Connoisseur)()
End Sub
如何使用 generics 寫一個 IFNotExistsAdd function
CS = {"test1","2"}
看起來像這樣
CS.IFNotExistsAdd(New Connoisseur() With{.Name="test1",.Pieces="1"}) 'This line will not be added because CS.Name already contains "test1"
CS.IFNotExistsAdd(New Connoisseur() With{.Name="test2",.Pieces="1"})
output 看起來像這樣
Output:
{"test1","2"}
{"test2","1"}
你的問題不是很清楚。 IFNotExistsAdd不是 List 的有效方法名稱,因此您必須創建擴展方法。
創建一個模塊(使用與調用類相同的命名空間)
Module Extensions
<Extension>
Public Sub IFNotExistsAdd(Of T)(list As List(Of T), item As T)
If Not list.Any(Function(x) x.Equals(item)) Then
list.Add(item)
End If
End Sub
End Module
然后您需要向 class 添加一個 Equals 覆蓋(我還為屬性添加了一個初始化程序)
Public Class Connoisseur
Public Name As String
Public Pieces As String
Public Sub New(name As String, pieces As String)
Me.Name = name
Me.Pieces = pieces
End Sub
Public Overrides Function Equals(obj As Object) As Boolean
If TypeOf obj Is Connoisseur Then
Return EqualsItem(CType(obj, Connoisseur))
Else
Return False
End If
End Function
Public Function EqualsItem(obj As Connoisseur) As Boolean
Return obj.Name = Me.Name And obj.Pieces = Me.Pieces
End Function
End Class
然后您可以運行將項目添加到列表中,它只會添加那些唯一的項目
CS.IFNotExistsAdd(New Connoisseur("test1", 1))
CS.IFNotExistsAdd(New Connoisseur("test1", 1))
CS.IFNotExistsAdd(New Connoisseur("test2", 2))
這只會添加 test1 和 test2。
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