ใช้ Event  CellFormatting ของ datagridview  ตัวอย่าง

private void dgvPositionList_CellFormatting(object sender, DataGridViewCellFormattingEventArgs e)
        {
            if (dgvPositionList.Columns[e.ColumnIndex].Name == "SalaryRate")  
            {
                e.CellStyle.Format = "#,##0";
                e.CellStyle.Alignment = DataGridViewContentAlignment.MiddleCenter;   // ตรงนี้ครับไปแก้ได้ว่าจะเอาซ้ายขวาตามใจชอบ
            }

            if (dgvPositionList.Columns[e.ColumnIndex].Name == "HourWage")
            {
                e.CellStyle.Format = "#,##0";
                e.CellStyle.Alignment = DataGridViewContentAlignment.MiddleCenter;
            }

            if (dgvPositionList.Columns[e.ColumnIndex].Name == "OTPerHour")
            {
                e.CellStyle.Format = "#,##0";
                e.CellStyle.Alignment = DataGridViewContentAlignment.MiddleCenter;
            }
        }