A column named [column name] already belongs to this DataTable in vb.net

I have the following code and I want to bind it to a DataGridView.

Public Class Form1
    Private _myTable As New DataTable()
    Private Sub LoadData()
        Dim item As New List(Of item())
        Grid.Bind(item)
    End Sub
    Private Sub FillDataTable(iRow As Integer, ByVal Codeproduct As String)
 _myTable.Columns.Add("No", GetType(Integer))
        _myTable.Columns.Add("Codeproduct", GetType(String))
        Dim row As DataRow = _myTable.NewRow()
        row("No") = iRow
        row("Codeproduct") = Codeproduct
        _myTable.Rows.Add(row)
    End Sub
    Private Sub AddColumnsProgrammatically()
        Dim Col1 = New DataGridViewTextBoxColumn()
        Dim Col2 = New DataGridViewTextBoxColumn()
        Col1.HeaderText = "No"
        Col1.Name = "Column1"
        Col1.DataPropertyName = "No"
        Col2.HeaderText = "CodeProduct"
        Col2.Name = "Column2"
        Col2.DataPropertyName = "CodeProduct"
        Grid.Columns.AddRange(New DataGridViewColumn() {Col1, Col2})
    End Sub
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        AddColumnsProgrammatically()
        LoadData()
    End Sub
    Private Sub TextBox1_KeyPress(sender As Object, e As KeyPressEventArgs) Handles TextBox1.KeyPress
        Dim iRow As Integer
        If Grid.RowCount - 1 = 0 Then
            iRow = 1
        Else
            iRow = Convert.ToInt32(Grid.Rows(Grid.RowCount - 2).Cells(0).Value.ToString()) + 1
        End If
        If e.KeyChar = Microsoft.VisualBasic.ChrW(Keys.Enter) Then
            FillDataTable(iRow, TextBox1.Text)
            Grid.DataSource = _myTable
            TextBox1.Clear()
        End If
    End Sub
End Class
Public Class DataControl
    Public Shared Function CreateDataTableDynamic(ByVal field() As String) As DataTable
        Dim i As Integer
        Dim dtTable As New DataTable("MyTable")
        For i = 0 To field.GetUpperBound(0)
            dtTable.Columns.Add(New DataColumn(field(i)))
        Next i
        Return dtTable
    End Function
End Class
Public Class item
    Public Property No() As Integer
    Public Property CodeProduct() As String
End Class

I want to ask if there is anything wrong with my code, and how can I bind my DataGridView to this data properly.

after add code "Columns.Add" and Fill the textbox in the second fill to DataGridView but still error

error when Fill the textbox in the second to DataGridView

[ breakpoint with diagnostic tool

[

In accordance with the guidelines of @jmcilhinney

 Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
_myTable.Columns.Add("No", GetType(Integer))
_myTable.Columns.Add("Codeproduct", GetType(String))
        AddColumnsProgrammatically()
        LoadData()
    End Sub