WPF Datagrid Manually change values Update issue

Hello guys,

Can't find a solution on the below issue.

I have a datagrid in WPF.  When the user changes manually the values of the columns "Units" and "Unit Price" I want an automatic calculation for the column "Amount".  But no matter what I do when I change Units for example and then I change cell with "TAB" or with the mouse click, I don't see any changes because the current "Units" cell still has the previous value.  But if I press enter and with the appropriate code of course, it works the amount changes.  I want when I press Enter, or Tab or left mouse click on another cell to have a successful "Amount" calculation on all three scenarios.

Below a screenshot of the datagrid and the code I tried so far.

The datagrid's source is a DataTable... purchasesDatagrid.ItemsSource = DataTablePurchases.DefaultView;

private async void purchasesDatagrid_CellEditEnding(object sender, DataGridCellEditEndingEventArgs e)
{
    try
    {
        await Task.Delay(100);

        int i = 0;
        foreach (DataRowView row in purchasesDatagrid.ItemsSource)
        {
            string Units_ = row["Units"] == null ? "0" : row["Units"].ToString();
            string UnitPrice_ = row["UnitPrice"] == null ? "0" : row["UnitPrice"].ToString();

            double Units = Regex.IsMatch(Units_, @"^[0-9.]+$") ? double.Parse(Units_) : 0;
            double UnitPrice = Regex.IsMatch(UnitPrice_, @"^[0-9.]+$") ? double.Parse(UnitPrice_) : 0;

            row["Amount"] = Units * UnitPrice;
        }
        DataTablePurchases.AcceptChanges();
        purchasesDatagrid.UpdateLayout();

        /* THIS IS ANOTHER APPROACH I TRIED: the cell and index are from a custom class that I use
        DataGridCell cell = GlobalEvents.DataGridHelper.GetCell(purchasesDatagrid.SelectedCells[0]);
        var index = GlobalEvents.DataGridHelper.GetRowIndex(cell);
        DataGridRow row = purchasesDatagrid.ItemContainerGenerator.ContainerFromIndex(index) as DataGridRow; //here we get the actual row at selected index
        DataRowView drvPurchases = (DataRowView)purchasesDatagrid.ItemContainerGenerator.ItemFromContainer(row); //here we get the actual data item behind the selected row
        string Units_ = drvPurchases["Units"] == null ? "0" : drvPurchases["Units"].ToString();
        double Units = Regex.IsMatch(Units_, @"^[0-9.]+$") ? double.Parse(Units_) : 0.00;
        string UnitPrice_ = drvPurchases["UnitPrice"] == null ? "0" : drvPurchases["UnitPrice"].ToString();
        double UnitPrice = Regex.IsMatch(UnitPrice_, @"^[0-9.]+$") ? double.Parse(UnitPrice_) : 0.00;
        drvPurchases["Amount"] = Units * UnitPrice;
        DataTablePurchases.Rows[index]["Amount"] = Units * UnitPrice;
        */
    }
    catch (Exception ex) {  }
}

Note that without async and the await Task it doesn't work at all.

I also tried events like below, but with no luck.

private void purchasesDatagrid_KeyDown(object sender, System.Windows.Input.KeyEventArgs e)
{
    if (e.Key.ToString() == "Return" || e.Key.ToString() == "Tab")
    {
        /* WITH THE SAME CODE LIKE IN FUNCTION ABOVE */
    }
}

private void purchasesDatagrid_CurrentCellChanged(object sender, EventArgs e)
{
    if (e.Key.ToString() == "Return" || e.Key.ToString() == "Tab")
    {
        /* WITH THE SAME CODE LIKE IN FUNCTION ABOVE */
    }
}