要在Visual Basic中展示国家和城市的项目，你可以使用以下解决方案：

1. 创建一个国家类和一个城市类，用于存储国家和城市的信息。例如，国家类可以包含国家的名称和人口数量，城市类可以包含城市的名称和所属国家。

Public Class Country
    Public Property Name As String
    Public Property Population As Integer
End Class

Public Class City
    Public Property Name As String
    Public Property Country As Country
End Class

2. 在主窗体中，创建国家和城市对象，并将它们添加到列表框中展示。

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    Dim country1 As New Country()
    country1.Name = "China"
    country1.Population = 1400000000

    Dim country2 As New Country()
    country2.Name = "USA"
    country2.Population = 330000000

    Dim city1 As New City()
    city1.Name = "Beijing"
    city1.Country = country1

    Dim city2 As New City()
    city2.Name = "New York"
    city2.Country = country2

    ListBox1.Items.Add(country1.Name)
    ListBox1.Items.Add(country2.Name)

    ListBox2.Items.Add(city1.Name)
    ListBox2.Items.Add(city2.Name)
End Sub

3. 当用户选择一个国家时，更新城市列表框以显示属于该国家的城市。

Private Sub ListBox1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ListBox1.SelectedIndexChanged
    ListBox2.Items.Clear()

    If ListBox1.SelectedIndex = 0 Then
        ListBox2.Items.Add("Beijing")
    ElseIf ListBox1.SelectedIndex = 1 Then
        ListBox2.Items.Add("New York")
    End If
End Sub

这样，当用户选择一个国家时，城市列表框将显示属于该国家的城市。你可以根据实际需求进行修改和扩展。