Thank you ,
Actually I found a way how to do this :
private void Format_GridColumns(RadGridView dgv_format)
{
foreach (GridViewDataColumn dCol in dgv_format.Columns)
{
if (dCol.DataType == typeof(DateTime))
{
if (dCol.FormatString.ToLower() == "{0}")
{
dCol.FormatString = "{0:d}";
}
}
if (dCol.DataType == typeof(Decimal))
{
if (dCol.FormatString.ToLower() == "{0}")
{
dCol.FormatString = "{0:N0}"; //"{0:N2}"
}
}
}
}
private void radGridView_1_CellFormatting(object sender, CellFormattingEventArgs e)
{
if (e.CellElement.ColumnIndex > 2)
{
e.CellElement.Text = String.Format("{0:N2}", ((GridDataCellElement)e.CellElement).Value);
}
}