private System.Data.DataTable table;
        void CreateTable(string[] columns)
        {
            table = new System.Data.DataTable();
            foreach (string col in columns)
            {
                table.Columns.Add(new System.Data.DataColumn(col));
            }
        }

        void AddRows(List<string[]> rows)
        {
            foreach (string[] row in rows)
            {
                System.Data.DataRow r = table.NewRow();
                for(int i=0;i<row.Length;i++)
                    r[i] = row[i];
                table.Rows.Add(r);
            }
        }

        void MakeGrid()
        {
            string[] cols ={ "First", "Second", "Third" };
            CreateTable(cols);//fills the data table with columns called First, Second and Third
            List<string[]> rows = new List<string[]>();
            string[] firstRow ={"1","2","3"};
            string[] secondRow ={"4","5","6"};
            string[] thirdRow ={ "7", "8", "9" };
            string[] fourthRow ={ "10", "11", "12" };
            rows.Add(firstRow);
            rows.Add(secondRow);
            rows.Add(thirdRow);
            rows.Add(fourthRow);
            AddRows(rows);//fills the data table with the rows according to the predefined columns
            this.dataGridView1.DataSource = table;//merge the datatable with the datagridview
        }