How to populate the third combobox (nested combobox)

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VB

MySQL

combobox

i have three combobox, combobox1 has preloaded list, based on what the combobox1 value will populate the combobox2. i have no errors on this, but when i try to populate combox3, it gives me "child list or field system cannot be created.

this is the code that were higlighted and gives the the error.

ComboBox3.DataSource = table2
ComboBox3.ValueMember = provincetext
ComboBox3.DisplayMember = provincetext



this is what i am trying to do

combobox1(region) <== preloaded list 
combobox2(province of selected value of region) <== code runs, no error (populated)
combobox3(municipality/city of selected value of province) <== error, (did not populate)

What I have tried:

Private Sub ComboBox1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ComboBox1.SelectedIndexChanged

        Dim regiontext As String
        regiontext = ComboBox1.Text
        Dim connection As New MySqlConnection("datasource=localhost;port=3306;username=root;password=")
        Dim adapter As New MySqlDataAdapter("select * from eulat.provinces", connection)
        Dim table As New DataTable()
        adapter.Fill(table)

        ComboBox2.DataSource = table
        ComboBox2.ValueMember = regiontext
        ComboBox2.DisplayMember = regiontext

    End Sub

    Private Sub ComboBox2_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ComboBox2.SelectedIndexChanged
        
        Dim provincetext As String
        provincetext = ComboBox2.Text
        Dim connection2 As New MySqlConnection("datasource=localhost;port=3306;username=root;password=")
        Dim adapter2 As New MySqlDataAdapter("select * from eulat.citymun", connection2)
        Dim table2 As New DataTable()
        adapter2.Fill(table2)

        ComboBox3.DataSource = table2
        ComboBox3.ValueMember = provincetext
        ComboBox3.DisplayMember = provincetext
       
    End Sub