Make empty DataGridView column cell values to zero (0) in VB.Net

Dear Sir,

I'm Trying to make empty datagridview column/cell directly values to zero(0) in VB.NET.

so I want when I make an empty column or cell in the DatagridView it immediately goes to zero (0).

Please Guide me

Thanks

Public Class Form2
    Public _myTable As New DataTable()
    Public _dr As DataRow
    Protected Overrides Sub OnLoad(e As EventArgs)
        MyBase.OnLoad(e)
        _myTable.Columns.AddRange({
                New DataColumn("Code", GetType(String)),
                New DataColumn("Quantity", GetType(Integer)),
                New DataColumn("Price", GetType(Integer)),
                New DataColumn("Discount", GetType(Integer)),
                New DataColumn("Total", GetType(Integer))})
        Me.CenterToScreen()
    End Sub
    Private Sub CalculateTotalqty()
        Dim tot As Double = 0
        For Each item As DataGridViewRow In DataGridView1.Rows
            Dim quantity As Double
            If Not IsDBNull(item.Cells("Quantity").Value) Then
                Integer.TryParse(CType(item.Cells("Quantity").Value, String), CInt(quantity))
            End If
            tot += quantity
        Next item
        lblQty.Text = tot.ToString("N2")
    End Sub
    Private Sub CalculateTotalValue()
        Dim tot As Double = 0
        For Each item As DataGridViewRow In DataGridView1.Rows
            Dim quantity As Double = 0
            Dim price As Double = 0
            Dim discount As Double = 0
            If Not IsDBNull(item.Cells("Quantity").Value) Then
                Integer.TryParse(CType(item.Cells("Quantity").Value, String), CInt(quantity))
            End If
            If Not IsDBNull(item.Cells("Price").Value) Then
                Integer.TryParse(CType(item.Cells("Price").Value, String), CInt(price))
            End If
            If Not IsDBNull(item.Cells("Discount").Value) Then
                Integer.TryParse(CType(item.Cells("Discount").Value, String), CInt(discount))
            End If
            tot += (quantity * price) - (discount)
        Next item
        lblValue.Text = tot.ToString("N")
    End Sub
    Private Sub BtnAddproduct_Click(sender As Object, e As EventArgs) Handles BtnAddproduct.Click
        _myTable.Rows.Add("A", 2, 10000, 0, 20000)
        'DataGridView1.AutoGenerateColumns = False
        ' Disable adding new row
        DataGridView1.AllowUserToAddRows = False
        ' Create our medium between grid and collection
        DataGridView1.DataSource = _myTable
        CalculateTotalqty()
        CalculateTotalValue()
    End Sub
 Private Sub datagridview1_CellEndEdit(sender As Object, e As DataGridViewCellEventArgs) Handles DataGridView1.CellEndEdit
        CalculateTotalqty()
        CalculateTotalValue()
        Dim price As Integer = Nothing, quantity As Integer = Nothing, Discount As Integer = Nothing, total As Integer = Nothing
        If DataGridView1.Rows(e.RowIndex).Cells("Quantity").Value IsNot Nothing Then
            If Not Integer.TryParse(DataGridView1.Rows(e.RowIndex).Cells("Quantity").Value.ToString(), quantity) Then
                quantity = 0
            End If
        Else
            quantity = 0
        End If
        If DataGridView1.Rows(e.RowIndex).Cells("Price").Value IsNot Nothing Then
            If Not Integer.TryParse(DataGridView1.Rows(e.RowIndex).Cells("Price").Value.ToString(), price) Then
                price = 0
            End If
        Else
            price = 0
        End If
        If DataGridView1.Rows(e.RowIndex).Cells("Discount").Value IsNot Nothing Then
            If Not Integer.TryParse(DataGridView1.Rows(e.RowIndex).Cells("Discount").Value.ToString(), Discount) Then
                Discount = 0
            End If
        Else
            Discount = 0
        End If
        total = (quantity * price) - (quantity * Discount)
        DataGridView1.Rows(e.RowIndex).Cells("Total").Value = total
    End Sub

    Private Sub DataGridView1_DataError(sender As Object, e As DataGridViewDataErrorEventArgs) Handles DataGridView1.DataError
        If e.Context = DataGridViewDataErrorContexts.Commit Then
            'MessageBox.Show(String.Format("Column {0} value is required.", e.ColumnIndex))
        End If
    End Sub
    Private Sub DataGridView1_CellBeginEdit(sender As Object, e As DataGridViewCellCancelEventArgs) Handles DataGridView1.CellBeginEdit
        _dr = _myTable.Rows(e.RowIndex)
    End Sub
End Sub