USING GRID for insert data from web form one by one

private DataTable CreateDataTable()
        {
            DataTable myDataTable = new DataTable();
            DataColumn myDataColumn;
            myDataColumn = new DataColumn();
            myDataColumn.DataType = Type.GetType("System.String");
            myDataColumn.ColumnName = "ItemName";
            myDataTable.Columns.Add(myDataColumn);
            myDataColumn = new DataColumn();
            myDataColumn.DataType = Type.GetType("System.String");
            myDataColumn.ColumnName = "ItemRate";
            myDataTable.Columns.Add(myDataColumn);
            myDataColumn = new DataColumn();
            myDataColumn.DataType = Type.GetType("System.String");
            myDataColumn.ColumnName = "ItemQty";
            myDataTable.Columns.Add(myDataColumn);
            //add records
            AddDataToTable("ItemName1", "ItemRate1", "ItemQty1", myDataTable);
            // In your case you can comment the above line and go like this
            //AddDataToTable(textBoxItemName.Text,ddlItemRate.SelectedValue, txtItemQty.Text,myDataTable);
            gvItems.DataSource = myDataTable;
            gvItems.DataBind();
            return myDataTable;
        }
        private void AddDataToTable(string strItemName, string strItemRate, string strItemQty, System.Data.DataTable myTable)
        {
            DataRow row;
            row = myTable.NewRow();
            row["ItemName"] = strItemName;
            row["ItemRate"] = strItemRate;
            row["ItemQty"] = strItemQty;
            myTable.Rows.Add(row);
        }