Kỹ thuật thao tác với List Collection

Sub Main()

Dim listID As New List(Of String) ‘ Declaration of list
Dim listID1 As New List(Of String)
Dim listID2 As New List(Of String)
Dim dictionaryID As New Dictionary(Of String, Integer) ‘ Declaration of dictionary

‘ Put key and value to dictionary
dictionaryID.Add("first", 1)
dictionaryID.Add("second", 2)
dictionaryID.Add("first1", 1)

‘ ① Using LINQ
‘ Reset Data of list
If listID IsNot Nothing Then
listID.Clear()
End If

‘ Get list Key of map data that have Value = 1
listID = (From kp As KeyValuePair(Of String, Integer) In dictionaryID
Where kp.Value = 1
Select kp.Key).ToList()

‘ Print data of list
For Each item In listID
Console.WriteLine("　　" & item)
Next

Console.WriteLine( "　" & "==========" )

‘ ② Using If with For Each pair In dictionaryID
‘ Khai báo biến lưu trữ cặp Key-Value cua map
Dim pair As KeyValuePair(Of String, Integer)

‘ Reset data of list
listID1.Clear()

‘ Get list Key of map data that have Value = 1
For Each pair In dictionaryID
If pair.Value = 1 Then
listID1.Add(pair.Key)
End If
Next

‘ Print data of list
For Each item In listID1
Console.WriteLine("　　" & item)
Next

Console.WriteLine( "　" & "==========" )

‘ ③ Using Lamba Expression
‘ Reset data of list
listID2.Clear()

‘ Get list Key of map data that have Value = 1
listID2 = dictionaryID.Where(Function(n) n.Value = 1).Select(Function(n) n.Key).ToList()

‘ Print data of list
For Each item In listID2
Console.WriteLine("　　" & item)
Next

Console.ReadKey()

End Sub

End Module
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