(DevExpress) xtragridview display in TextEdit the total sum of specific column

Question

I have a textedit named = MaterialsTextEdit and I have a button that can add/pass the value from the MaterialsTextEdit directly into the table(gridView). I want to display the total sum of Materials column in TotalMaterialsTextEdit. But it doesn't worked. I used these codes. Please tell me what's wrong? Thank you in advance. Happy coding :)

Public Class FORM
    Dim dt As New DataTable("Table")
    Private Sub FORM_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        InitializeApps()
        GetTable()
    End Sub

    Private Sub FORM_Shown(sender As Object, e As EventArgs) Handles MyBase.Shown
        GetSummary()
    End Sub

    Sub GetSummary()
        Me.gridView.Columns("Materials").Summary.Add(DevExpress.Data.SummaryItemType.Sum)
        gridView.Columns("Materials").SummaryItem.DisplayFormat = "{0:0,0}"
        Dim a = gridView.Columns("Materials").SummaryItem.SummaryValue
        Me.textEdit.EditValue = a
    End Sub

    Sub GetTable()
        dt.Columns.Add("Materials", GetType(Double))
        gridView.DataSource = dt
    End Sub

    Private Sub AddtoTableSimpleButton_Click(sender As Object, e As EventArgs) Handles AddtoTableSimpleButton.Click
        dt.Rows.Add(Double.Parse(MaterialsTextEdit.Text))
        OBTAFormGridControl.DataSource = dt
    End Sub

    Private Sub gridView_CellValueChanged(sender As Object, e As Views.Base.CellValueChangedEventArgs) Handles gridView.CellValueChanged
        gridView.UpdateTotalSummary()
        Me.TotalMaterialsTextEdit.EditValue = gridView.Columns("Materials").SummaryItem.SummaryValue
    End Sub
End Class