Set AutoSize for columns to multiple sheets about npoi

[yang-xiaodong]

Duplicated of #26

[pedrofernandesfilho]

For me does not seem to be duplicated.
I have many spreadsheets in the same file (xlsx) and autosize doesn't not work at all.

[KiritoStudio]

@pedrofernandesfilho Maybe custom column for each line is the workaround.

                for (int k = 0; k <= dt.Columns.Count; k++)
                {
                    sheet1.AutoSizeColumn(i);
                }

                for (int columnNum = 0; columnNum <= dt.Columns.Count; columnNum++)
                {
                    int columnWidth = sheet1.GetColumnWidth(columnNum) / 256;
                    for (int rowNum = 0; rowNum <= sheet1.LastRowNum; rowNum++)
                    {
                        IRow currentRow;
                        if (sheet1.GetRow(rowNum) == null)
                        {
                            currentRow = sheet1.CreateRow(rowNum);
                        }
                        else
                        {
                            currentRow = sheet1.GetRow(rowNum);
                        }

                        if (currentRow.GetCell(columnNum) != null)
                        {
                            ICell currentCell = currentRow.GetCell(columnNum);
                            int length = Encoding.GetEncoding("gb18030").GetBytes(currentCell.ToString()).Length;
                            if (columnWidth < length)
                            {
                                columnWidth = length;
                            }
                        }
                    }
                    sheet1.SetColumnWidth(columnNum, columnWidth * 256);
                }