How to export DataTable to Excel

Question

How can I export a DataTable to Excel in C#? I am using Windows Forms. The DataTable is associated with a DataGridView control. I have

Answer 1

Using DocumentFormat.OpenXml nuget package, I have created a singleton class which handles export to excel from either a DataTable or DataSet. Tables will be represented as separate sheets in a workbook.

The main class

public sealed class OfficeOpenXML
    {
        private static Lazy _instance = new Lazy(() => new OfficeOpenXML());
        private OfficeOpenXML()
        {

        }
        public static OfficeOpenXML GetInstance()
        {
            return _instance.Value;
        }

        public MemoryStream GetExcelStream(DataSet ds, bool firstRowAsHeader = false)
        {
            if (ds == null || ds.Tables.Count == 0)
            {
                return null;
            }

            MemoryStream stream = new MemoryStream();
            using (var excel = SpreadsheetDocument.Create(stream, SpreadsheetDocumentType.Workbook))
            {
                //create doc and workbook
                WorkbookPart workbookPart = excel.AddWorkbookPart();
                Workbook workbook = new Workbook();
                Sheets sheets = new Sheets();
                //loop all tables in the dataset
                for (int iTable = 0; iTable < ds.Tables.Count; iTable++)
                {
                    var table = ds.Tables[iTable];
                    //create sheet part
                    WorksheetPart worksheetPart = workbookPart.AddNewPart();
                    Worksheet worksheet = new Worksheet();
                    SheetData data = new SheetData();
                    List allRows = new List();

                    //setting header of the sheet
                    Row headerRow = new Row() { RowIndex = 1 };
                    for (int iColumn = 0; iColumn < table.Columns.Count; iColumn++)
                    {
                        var col = table.Columns[iColumn];
                        //if first row of table is not the header then set columns of table as header of sheet
                        if (!firstRowAsHeader)
                        {
                            headerRow.Append(new Cell
                            {
                                DataType = CellValues.String,
                                CellValue = new CellValue(col.ColumnName)
                            });
                        }
                        else
                        {
                            headerRow.Append(new Cell
                            {
                                DataType = CellValues.String,
                                CellValue = new CellValue(Convert.ToString(table.Rows[0][col]))
                            });
                        }
                    }
                    allRows.Add(headerRow);

                    //setting other data rows
                    if (table.Rows != null && table.Rows.Count != 0)
                    {
                        for (int iRow = firstRowAsHeader ? 1 : 0; iRow < table.Rows.Count; iRow++)
                        {
                            var row = table.Rows[iRow];
                            Row valueRow = new Row { RowIndex = (uint)(iRow + (firstRowAsHeader ? 1 : 2)) };

                            for (int iColumn = 0; iColumn < table.Columns.Count; iColumn++)
                            {
                                var col = table.Columns[iColumn];
                                valueRow.Append(new Cell
                                {
                                    DataType = Format(col.DataType),
                                    CellValue = new CellValue(Convert.ToString(row[col]))
                                });
                            }
                            allRows.Add(valueRow);
                        }
                    }

                    //add rows to the data
                    data.Append(allRows);
                    worksheet.Append(data);
                    worksheetPart.Worksheet = worksheet;
                    worksheetPart.Worksheet.Save();

                    //add worksheet to main sheets
                    sheets.Append(new Sheet
                    {
                        Name = string.IsNullOrWhiteSpace(table.TableName) ? "Sheet" + (iTable + 1) : table.TableName,
                        Id = workbookPart.GetIdOfPart(worksheetPart),
                        SheetId = (uint)iTable + 1
                    });
                }//single table processing ends here

                //add created sheets to workbook
                workbook.Append(sheets);
                excel.WorkbookPart.Workbook = workbook;
                excel.WorkbookPart.Workbook.Save();


                excel.Close();
            }
            stream.Seek(0, SeekOrigin.Begin);    
            return stream;


        }
        public MemoryStream GetExcelStream(DataTable dt, bool firstRowAsHeader = false)
        {
            DataSet ds = new DataSet();
            ds.Tables.Add(dt);
            return GetExcelStream(ds, firstRowAsHeader);
        }



        #region Excel Helpers

        CellValues Format(Type t)
        {

            switch (t.ToString())
            {

                case "System.String":
                    return CellValues.String;
                case "System.DateTime":
                    return CellValues.Date;
                case "System.Boolean":
                    return CellValues.Boolean;
                case "System.Int16":
                    return CellValues.Number;
                case "System.Int32":
                    return CellValues.Number;
                case "System.Int64":
                    return CellValues.Number;
                case "System.UInt16":
                    return CellValues.Number;
                case "System.UInt32":
                    return CellValues.Number;
                case "System.UInt64":
                    return CellValues.Number;
                case "System.Decimal":
                    return CellValues.Number;
                case "System.Double":
                    return CellValues.Number;
                case "System.Single":
                    return CellValues.Number;
                default:
                    return CellValues.String;
            }
        }
        #endregion
    }

Save to a file

        var excelApp = OfficeOpenXML.GetInstance();
        var dt = GetDataTableFromDB();
        using (var stream = excelApp.GetExcelStream(dt, false))//use true to hide datatable columns from excel
        {

            using (FileStream fs = new FileStream(@"C:\Users\Public\myexcel.xlsx", FileMode.Create))
            {
                stream.CopyTo(fs);
                fs.Flush();
            }
        }

Download in an MVC application

public ActionResult DownloadReport()
{
    var ds = GetDataSetFromDB();
    var excelApp = OfficeOpenXML.GetInstance();
    var file = excelApp.GetExcelStream(ds, false);
    return File(file, "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet", Guid.NewGuid().ToString() + ".xlsx");
}