Handle it on gridview rowdatabound event.
protected void RowDataBound(object sender, GridViewRowEventArgs e)
{
if (e.Row.RowType == DataControlRowType.DataRow)
{
e.Row.Cells[0].Text = e.Row.Cells[0].Text.Split('.')[0].ToString() + "." + e.Row.Cells[0].Text.Split('.')[1].Substring(0, 1);
}
}