Kỹ thuật thao tác với List Collection

Module MinhHoangBlog

    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