Como exportar DataTable para Excel

Como posso exportar um DataTablepara o Excel em C #? Estou usando o Windows Forms. O DataTableestá associado a um DataGridViewcontrole. Tenho que exportar registros DataTablepara o Excel.

Eu recomendaria ClosedXML -

Você pode transformar um DataTable em uma planilha do Excel com algum código muito legível:

XLWorkbook wb = new XLWorkbook();
DataTable dt = GetDataTableOrWhatever();
wb.Worksheets.Add(dt,"WorksheetName");

O desenvolvedor é responsivo e útil. O projeto é desenvolvido ativamente e a documentação é excelente.

Experimente um código simples para converter DataTable em arquivo excel como csv:

var lines = new List<string>();

string[] columnNames = dataTable.Columns
    .Cast<DataColumn>()
    .Select(column => column.ColumnName)
    .ToArray();

var header = string.Join(",", columnNames.Select(name => $"\"{name}\""));
lines.Add(header);

var valueLines = dataTable.AsEnumerable()
    .Select(row => string.Join(",", row.ItemArray.Select(val => $"\"{val}\"")));

lines.AddRange(valueLines);

File.WriteAllLines("excel.csv", lines);

Isso gravará um novo arquivo excel.csvno diretório de trabalho atual, que geralmente é onde o .exe está ou de onde você o inicia.

Uma opção elegante é escrever um método de extensão (veja abaixo) para a classe DataTable da estrutura .net.

Este método de extensão pode ser chamado da seguinte maneira:

using System;
using System.Collections.Generic;
using System.Linq;
using Excel = Microsoft.Office.Interop.Excel;
using System.Data;
using System.Data.OleDb;

DataTable dt;
// fill table data in dt here 
...

// export DataTable to excel
// save excel file without ever making it visible if filepath is given
// don't save excel file, just make it visible if no filepath is given
dt.ExportToExcel(ExcelFilePath);

Método de extensão para a classe DataTable:

public static class My_DataTable_Extensions
{

    // Export DataTable into an excel file with field names in the header line
    // - Save excel file without ever making it visible if filepath is given
    // - Don't save excel file, just make it visible if no filepath is given
    public static void ExportToExcel(this DataTable tbl, string excelFilePath = null) {
        try {
            if (tbl == null || tbl.Columns.Count == 0)
                throw new Exception("ExportToExcel: Null or empty input table!\n");

            // load excel, and create a new workbook
            var excelApp = new Excel.Application();
            excelApp.Workbooks.Add();

            // single worksheet
            Excel._Worksheet workSheet = excelApp.ActiveSheet;

            // column headings
            for (var i = 0; i < tbl.Columns.Count; i++) {
                workSheet.Cells[1, i + 1] = tbl.Columns[i].ColumnName;
            }

            // rows
            for (var i = 0; i < tbl.Rows.Count; i++) {
                // to do: format datetime values before printing
                for (var j = 0; j < tbl.Columns.Count; j++) {
                    workSheet.Cells[i + 2, j + 1] = tbl.Rows[i][j];
                }
            }

            // check file path
            if (!string.IsNullOrEmpty(excelFilePath)) {
                try {
                    workSheet.SaveAs(excelFilePath);
                    excelApp.Quit();
                    MessageBox.Show("Excel file saved!");
                }
                catch (Exception ex) {
                    throw new Exception("ExportToExcel: Excel file could not be saved! Check filepath.\n"
                                        + ex.Message);
                }
            } else { // no file path is given
                excelApp.Visible = true;
            }
        }
        catch (Exception ex) {
            throw new Exception("ExportToExcel: \n" + ex.Message);
        }
    }
}

Solução baseada no artigo tuncalik (obrigado pela ideia), mas no caso de mesas grandes está funcionando muito mais rápido (e é um pouco menos claro).

public static class My_DataTable_Extensions
{
    /// <summary>
    /// Export DataTable to Excel file
    /// </summary>
    /// <param name="DataTable">Source DataTable</param>
    /// <param name="ExcelFilePath">Path to result file name</param>
    public static void ExportToExcel(this System.Data.DataTable DataTable, string ExcelFilePath = null)
    {
        try
        {
            int ColumnsCount;

            if (DataTable == null || (ColumnsCount = DataTable.Columns.Count) == 0)
                throw new Exception("ExportToExcel: Null or empty input table!\n");

            // load excel, and create a new workbook
            Microsoft.Office.Interop.Excel.Application Excel = new Microsoft.Office.Interop.Excel.Application();
            Excel.Workbooks.Add();

            // single worksheet
            Microsoft.Office.Interop.Excel._Worksheet Worksheet = Excel.ActiveSheet;

            object[] Header = new object[ColumnsCount];

            // column headings               
            for (int i = 0; i < ColumnsCount; i++)
                Header[i] = DataTable.Columns[i].ColumnName;

            Microsoft.Office.Interop.Excel.Range HeaderRange = Worksheet.get_Range((Microsoft.Office.Interop.Excel.Range)(Worksheet.Cells[1, 1]), (Microsoft.Office.Interop.Excel.Range)(Worksheet.Cells[1, ColumnsCount]));
            HeaderRange.Value = Header;
            HeaderRange.Interior.Color = System.Drawing.ColorTranslator.ToOle(System.Drawing.Color.LightGray);
            HeaderRange.Font.Bold = true;

            // DataCells
            int RowsCount = DataTable.Rows.Count;
            object[,] Cells = new object[RowsCount, ColumnsCount];

            for (int j = 0; j < RowsCount; j++)
                for (int i = 0; i < ColumnsCount; i++)
                    Cells[j, i] = DataTable.Rows[j][i];

            Worksheet.get_Range((Microsoft.Office.Interop.Excel.Range)(Worksheet.Cells[2, 1]), (Microsoft.Office.Interop.Excel.Range)(Worksheet.Cells[RowsCount + 1, ColumnsCount])).Value = Cells;

            // check fielpath
            if (ExcelFilePath != null && ExcelFilePath != "")
            {
                try
                {
                    Worksheet.SaveAs(ExcelFilePath);
                    Excel.Quit();
                    System.Windows.MessageBox.Show("Excel file saved!");
                }
                catch (Exception ex)
                {
                    throw new Exception("ExportToExcel: Excel file could not be saved! Check filepath.\n"
                        + ex.Message);
                }
            }
            else    // no filepath is given
            {
                Excel.Visible = true;
            }
        }
        catch (Exception ex)
        {
            throw new Exception("ExportToExcel: \n" + ex.Message);
        }
    }
}

Tente esta função passar a tabela de dados e o caminho do arquivo para onde você deseja exportar

public void CreateCSVFile(ref DataTable dt, string strFilePath)
{            
    try
    {
        // Create the CSV file to which grid data will be exported.
        StreamWriter sw = new StreamWriter(strFilePath, false);
        // First we will write the headers.
        //DataTable dt = m_dsProducts.Tables[0];
        int iColCount = dt.Columns.Count;
        for (int i = 0; i < iColCount; i++)
        {
            sw.Write(dt.Columns[i]);
            if (i < iColCount - 1)
            {
                sw.Write(",");
            }
        }
        sw.Write(sw.NewLine);

        // Now write all the rows.

        foreach (DataRow dr in dt.Rows)
        {
            for (int i = 0; i < iColCount; i++)
            {
                if (!Convert.IsDBNull(dr[i]))
                {
                    sw.Write(dr[i].ToString());
                }
                if (i < iColCount - 1)
                {
                    sw.Write(",");
                }
            }

            sw.Write(sw.NewLine);
        }
        sw.Close();
    }
    catch (Exception ex)
    {
        throw ex;
    }
}

A melhor e mais fácil maneira

private void exportToExcel(DataTable dt)
    {

        /*Set up work book, work sheets, and excel application*/
        Microsoft.Office.Interop.Excel.Application oexcel = new Microsoft.Office.Interop.Excel.Application();
        try
        {
            string path = AppDomain.CurrentDomain.BaseDirectory;
            object misValue = System.Reflection.Missing.Value;
            Microsoft.Office.Interop.Excel.Workbook obook = oexcel.Workbooks.Add(misValue);
            Microsoft.Office.Interop.Excel.Worksheet osheet = new Microsoft.Office.Interop.Excel.Worksheet();


          //  obook.Worksheets.Add(misValue);

            osheet = (Microsoft.Office.Interop.Excel.Worksheet)obook.Sheets["Sheet1"];
            int colIndex = 0;
            int rowIndex = 1;

            foreach (DataColumn dc in dt.Columns)
            {
                colIndex++;
                osheet.Cells[1, colIndex] = dc.ColumnName;
            }
            foreach (DataRow dr in dt.Rows)
            {
                rowIndex++;
                colIndex = 0;

                foreach (DataColumn dc in dt.Columns)
                {
                    colIndex++;
                    osheet.Cells[rowIndex, colIndex] = dr[dc.ColumnName];
                }
            }

            osheet.Columns.AutoFit();
            string filepath = "C:\\Temp\\Book1";

            //Release and terminate excel

            obook.SaveAs(filepath);
            obook.Close();
            oexcel.Quit();
            releaseObject(osheet);

            releaseObject(obook);

            releaseObject(oexcel);
            GC.Collect();
        }
        catch (Exception ex)
        {
            oexcel.Quit();
            log.AddToErrorLog(ex, this.Name);
        }
    }

Excel Interop:

Este método evita que as datas sejam invertidas de dd-mm-aaaa para mm-dd-aaaa

public bool DataTableToExcelFile(DataTable dt, string targetFile)
{
    const bool dontSave = false;
    bool success = true;

    //Exit if there is no rows to export
    if (dt.Rows.Count == 0) return false;

    object misValue = System.Reflection.Missing.Value;
    List<int> dateColIndex = new List<int>();
    Excel.Application excelApp = new Excel.Application();
    Excel.Workbook excelWorkBook = excelApp.Workbooks.Add(misValue);
    Excel.Worksheet excelWorkSheet = excelWorkBook.Sheets("sheet1");

    //Iterate through the DataTable and populate the Excel work sheet
    try {
        for (int i = -1; i <= dt.Rows.Count - 1; i++) {
            for (int j = 0; j <= dt.Columns.Count - 1; j++) {
                if (i < 0) {
                    //Take special care with Date columns
                    if (dt.Columns(j).DataType is typeof(DateTime)) {
                        excelWorkSheet.Cells(1, j + 1).EntireColumn.NumberFormat = "d-MMM-yyyy;@";
                        dateColIndex.Add(j);
                    } 
                    //else if ... Feel free to add more Formats

                    else {
                        //Otherwise Format the column as text
                        excelWorkSheet.Cells(1, j + 1).EntireColumn.NumberFormat = "@";
                    }
                    excelWorkSheet.Cells(1, j + 1) = dt.Columns(j).Caption;
                } 
                else if (dateColIndex.IndexOf(j) > -1) {
                    excelWorkSheet.Cells(i + 2, j + 1) = Convert.ToDateTime(dt.Rows(i).ItemArray(j)).ToString("d-MMM-yyyy");
                } 
                else {
                    excelWorkSheet.Cells(i + 2, j + 1) = dt.Rows(i).ItemArray(j).ToString();
                }
            }
        }

        //Add Autofilters to the Excel work sheet  
        excelWorkSheet.Cells.AutoFilter(1, Type.Missing, Excel.XlAutoFilterOperator.xlAnd, Type.Missing, true);
        //Autofit columns for neatness
        excelWorkSheet.Columns.AutoFit();
        if (File.Exists(exportFile)) File.Delete(exportFile);
        excelWorkSheet.SaveAs(exportFile);
    } catch {
        success = false;
    } finally {
        //Do this irrespective of whether there was an exception or not. 
        excelWorkBook.Close(dontSave);
        excelApp.Quit();
        releaseObject(excelWorkSheet);
        releaseObject(excelWorkBook);
        releaseObject(excelApp);
    }
    return success;
}

Se você não se preocupa com a inversão das datas, use o link consulte que mostra como preencher todas as células na planilha do Excel em uma linha de código:

Excel Interop - Eficiência e desempenho

CSV:

public string DataTableToCSV(DataTable dt, bool includeHeader, string rowFilter, string sortFilter, bool useCommaDelimiter = false, bool truncateTimesFromDates = false)
{
    dt.DefaultView.RowFilter = rowFilter;
    dt.DefaultView.Sort = sortFilter;
    DataView dv = dt.DefaultView;
    string csv = DataTableToCSV(dv.ToTable, includeHeader, useCommaDelimiter, truncateTimesFromDates);
    //reset the Filtering
    dt.DefaultView.RowFilter = string.Empty;
    return csv;
}

public string DataTableToCsv(DataTable dt, bool includeHeader, bool useCommaDelimiter = false, bool truncateTimesFromDates = false)
{
    StringBuilder sb = new StringBuilder();
    string delimter = Constants.vbTab;
    if (useCommaDelimiter)
        delimter = ",";

    if (includeHeader) {
        foreach (DataColumn dc in dt.Columns) {
            sb.AppendFormat("{0}" + Constants.vbTab, dc.ColumnName);
        }

        //remove the last Tab
        sb.Remove(sb.ToString.Length - 1, 1);
        sb.Append(Environment.NewLine);
    }

    foreach (DataRow dr in dt.Rows) {
        foreach (DataColumn dc in dt.Columns) {
            if (Information.IsDate(dr(dc.ColumnName).ToString()) & dr(dc.ColumnName).ToString().Contains(".") == false & truncateTimesFromDates) {
                sb.AppendFormat("{0}" + delimter, Convert.ToDateTime(dr(dc.ColumnName).ToString()).Date.ToShortDateString());
            } else {
                sb.AppendFormat("{0}" + delimter, CheckDBNull(dr(dc.ColumnName).ToString().Replace(",", "")));
            }
        }
        //remove the last Tab
        sb.Remove(sb.ToString.Length - 1, 1);
        sb.Append(Environment.NewLine);
    }
    return sb.ToString;
}

public enum enumObjectType
{
    StrType = 0,
    IntType = 1,
    DblType = 2
}

public object CheckDBNull(object obj, enumObjectType ObjectType = enumObjectType.StrType)
{
    object objReturn = null;
    objReturn = obj;
    if (ObjectType == enumObjectType.StrType & Information.IsDBNull(obj)) {
        objReturn = "";
    } else if (ObjectType == enumObjectType.IntType & Information.IsDBNull(obj)) {
        objReturn = 0;
    } else if (ObjectType == enumObjectType.DblType & Information.IsDBNull(obj)) {
        objReturn = 0.0;
    }
    return objReturn;
}

Basta fazer uso da Biblioteca CloseMXL.Excel . É fácil e muito rápido também.

Classe

private DataTable getAllList()
        {
            string constr = ConfigurationManager.ConnectionStrings["RConnection"].ConnectionString;
            using (SqlConnection con = new SqlConnection(constr))
            {
                using (SqlCommand cmd = new SqlCommand("SELECT EmpId, gender, EmpName, pOnHold FROM Employee  WHERE EmpId= '"+ AnyVariable + "' ORDER BY EmpName"))
                {
                    using (SqlDataAdapter da = new SqlDataAdapter())
                    {
                        DataTable dt = new DataTable();
                        cmd.CommandType = CommandType.Text;
                        cmd.Connection = con;
                        da.SelectCommand = cmd;
                        da.Fill(dt);
                        dt.Columns[0].ColumnName = "Employee Id";
                        dt.Columns[1].ColumnName = "Gender";
                        dt.Columns[2].ColumnName = "Employee Name";
                        dt.Columns[3].ColumnName = "On Hold";

                        return dt;
                    }
                }
            }
        }

Em seguida, outro método que obtém o conjunto de dados

public DataSet getDataSetExportToExcel()
        {
            DataSet ds = new DataSet();
            DataTable dtEmp = new DataTable("CLOT List");
            dtEmp = getAllList();
             ds.Tables.Add(dtEmp);
             ds.Tables[0].TableName = "Employee"; //If you which to use Mutliple Tabs
             return ds;
          }

Agora você botão Click Event

protected void btn_Export_Click(object sender, EventArgs e)
        {
            DataSet ds = getDataSetExportToExcel();

            using (XLWorkbook wb = new XLWorkbook())
            {
                wb.Worksheets.Add(ds);
                wb.Style.Alignment.Horizontal = XLAlignmentHorizontalValues.Center;
                wb.Style.Font.Bold = true;

                Response.Clear();
                Response.Buffer = true;
                Response.Charset = "";
                Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
                Response.AddHeader("content-disposition", "attachment;filename=EmployeeonHoldList.xlsx");

                using (MemoryStream MyMemoryStream = new MemoryStream())
                {
                    wb.SaveAs(MyMemoryStream);
                    MyMemoryStream.WriteTo(Response.OutputStream);

                    Response.Flush();
                    Response.End();
                }
            }
        }

Você pode usar minha biblioteca SwiftExcel . É especialmente bom quando o desempenho e o baixo uso de memória ocorrem, pois grava dados diretamente no arquivo:

using (var ew = new ExcelWriter("C:\\temp\\test.xlsx"))
{
    for (var row = 1; row <= 100; row++)
    {
        for (var col = 1; col <= 10; col++)
        {
            ew.Write($"row:{row}-col:{col}", col, row);
        }
    }
}

Comando Nuget para instalar:

Install-Package SwiftExcel

Eu queria adicionar esta resposta porque gastei muito tempo procurando um método rápido e confiável para fazer isso e nenhum exemplo completo do uso de OpenXMLWriter para essa finalidade existia em qualquer lugar que eu pudesse encontrar.

Em primeiro lugar, COM / Interop (que muitas das outras respostas usam) é adequado para esse propósito, mas sofre de algumas sensibilidades. Eu o uso há décadas e ele é praticamente estável, mas ao implementar um front-end de data warehouse para centenas de usuários, descobri que ele estava sujeito a muitos problemas, dependendo da máquina e do que o usuário fazia, então mudei para OpenXML. OpenXML DOM é bastante bom para esse propósito, mas é mais lento do que usar OpenXMLWriter. Quando você entra em grandes conjuntos de dados (100K +) com muitas colunas, o DOM é muito mais lento do que o OpenXMLWriter, então eu uso o último. O método abaixo grava mais de 420 mil linhas com mais de 30 campos em menos de 30 segundos.

Espero que os comentários sejam suficientes para orientar qualquer pessoa sobre o que está fazendo. Ele é simplificado, pois grava todos os valores no arquivo como strings, mas você pode implementar a lógica para gravar vários tipos de dados (e usar vários formatos de células) com base no conteúdo dos seus dados. Você também pode adaptar isso para uso em um DataGridView (em vez de um DataTable) alterando apenas algumas coisas (ou seja, os loops através de colunas / linhas).

É necessária uma referência a DocumentFormat.OpenXML (d / l com OpenXML SDK) e WindowsBase.

Imports DocumentFormat.OpenXml
Imports DocumentFormat.OpenXml.Spreadsheet
Imports DocumentFormat.OpenXml.Packaging

Public Sub ExportToExcelXML(ByRef dt As DataTable, filename As String)
    Dim wbp As WorkbookPart, wsp As WorksheetPart
    'If this DataTable has more rows in it than can fit in Excel, throw an exception
    If dt.Rows.Count > 1048575 Then Throw New Exception("The DataTable is too large to export to Excel.")
    'Delete any previous file of the same name that may exist.
    File.Delete(filename)
    'Create an OpenXML SpreadsheetDocument...
    Using xls = SpreadsheetDocument.Create(filename, SpreadsheetDocumentType.Workbook)
        'Add a WorkbookPart to the Spreadsheet Doc, then add a WorksheetPart to the WorkbookPart.
        wbp = xls.AddWorkbookPart()
        wsp = wbp.AddNewPart(Of WorksheetPart)
        'Now we need to add the "StyleSheet" to the WorkbookPart (that we just added above). This will allow us to apply formatting to our Cells.
        'Add the WbStylesPart and the StyleSheet.
        Dim stp As WorkbookStylesPart = wbp.AddNewPart(Of WorkbookStylesPart)
        Dim ss As New Stylesheet
        'Create the only two Fonts we're going to use (Regular and Bold).
        Dim fBold As New Font
        fBold.Append(New Bold)
        Dim fnts As New Fonts
        fnts.Append(New Font) 'This creates the default (unmodified, regular) Font. It's added first, so its index is 0.
        fnts.Append(fBold) 'This creates the Bold font. It's added second, so its index is 1.
        'Create the default Fill/Border settings (these have to be here, even though I don't set any custom fills/borders).
        Dim flls As New Fills
        Dim brdrs As New Borders
        flls.Append(New Fill)
        brdrs.Append(New Border)
        'Now I have to add formats (NumberFormat and CellFormat). First, you create a NumberFormat. This is basically the pattern of 
        '   the format (i.e. "@" for Text). For now, I only need a Text format, but I can add more patterns if needed.
        '   I give the format an ID of 164, since 163 is where the built-in Excel formats end.
        Dim nbrfmts As New NumberingFormats
        nbrfmts.Append(New NumberingFormat With {.NumberFormatId = 164, .FormatCode = "@"})
        'Create the first two CellFormats: Default, which will have an index of 0 and "Header" (Bold/Centered) with an index of 1.
        Dim cellfmts As New CellFormats()
        cellfmts.Append(New CellFormat() With {.FontId = 0, .NumberFormatId = 164, .FillId = 0, .BorderId = 0})
        cellfmts.Append(New CellFormat() With {.FontId = 1, .NumberFormatId = 164,
            .Alignment = New Alignment() With {.WrapText = True, .Horizontal = HorizontalAlignmentValues.Center}})
        'Add all of the Fonts/Fills/Borders/etc to the StyleSheet and add it all to the WorkbookStylesPart.
        ss.Append(fnts)
        ss.Append(flls)
        ss.Append(brdrs)
        ss.Append(cellfmts)
        ss.NumberingFormats = nbrfmts
        stp.Stylesheet = ss
        stp.Stylesheet.Save()
        'Now create an OpenXMLWriter using the WorksheetPart to write the cells to the worksheet.
        Using oxw As OpenXmlWriter = OpenXmlWriter.Create(wsp)
            'Write the start element for the Worksheet and the Columns...
            oxw.WriteStartElement(New Worksheet)
            oxw.WriteStartElement(New Columns())
            'Now I'm going to loop through the columns in the DataTable...
            For c As Integer = 0 To dt.Columns.Count - 1
                'Now we'll get the width for the column. To do this, we loop through all of the rows and measure the width of the text 
                '   using the default Excel Font (currently Font: Calibri Size: 11) and return the largest width (in pixels) to use below.
                '   Why not do this loop below (when I loop through the rows to write the Cells)? Because you can't. You have to
                '   write the Column XML first before writing the SheetData/Row/Cell XML (I confirmed this by trying it), so there's
                '   no way (that I'm aware of) to avoid looping through all of the rows twice if you want to AutoFit.
                'Setup vars we'll use for getting the column widths (below).
                Dim g = System.Drawing.Graphics.FromHwnd(IntPtr.Zero)
                Dim fnt = New System.Drawing.Font("Calibri", 11)
                Dim wid As Double = 0
                'Get the width of the header (because if this is wider than the widest value, we'll use the header text's width).
                '   I found that adding 2 pixels to the width was necessary to get the column as wide as Excel would make it.
                Dim tmp As Double = g.MeasureString(dt.Columns(c).ColumnName, New System.Drawing.Font(fnt, System.Drawing.FontStyle.Bold)).Width + 2
                'Loop through the rows in the dt and get the width of the value in that row/col. If it's wider than the widest
                '   width we've encountered thus far, use the new wider width as our basis.
                For Each row As DataRow In dt.Rows
                    If tmp > wid Then wid = tmp
                    tmp = g.MeasureString(row(c).ToString, fnt).Width
                Next
                'Set the column attributes and write it to the file. The Width is set using a formula that converts from pixels to Excel's column width values.
                Dim oxa As New List(Of OpenXmlAttribute) From {New OpenXmlAttribute("min", Nothing, c + 1), New OpenXmlAttribute("max", Nothing, c + 1),
                    New OpenXmlAttribute("width", Nothing, System.Math.Round((wid - 12 + 5) / 7D + 1, 2))}
                oxw.WriteStartElement(New Column(), oxa)
                oxw.WriteEndElement()
            Next
            'CLose out the Columns collection.
            oxw.WriteEndElement()
            'Write the start element for the SheetData...
            oxw.WriteStartElement(New SheetData)
            'Write the start element for the Header row.
            oxw.WriteStartElement(New Row)
            'Loop through the Columns in the dt.
            For Each col As DataColumn In dt.Columns
                'Write a cell for this column's Header. All Header cells are written with a DataType of String ("str"). 
                '   I ALSO apply the "Header" CellFormat (StyleIndex 1) to all of the Header Cells. This makes them Bold and Centered.
                WriteCell(oxw, col.ColumnName, "str", 1)
            Next
            'Close out the Header row.
            oxw.WriteEndElement()
            'Loop through all of the rows in the dt...
            For Each row As DataRow In dt.Rows
                'Write a StartElement for this row...
                oxw.WriteStartElement(New Row)
                'Loop through all of the columns in the dt...
                For c As Integer = 0 To dt.Columns.Count - 1
                    'Write a value in this row/column to the Excel file. I use the datatype of "String" and the default CellFormat/StyleIndex.
                    WriteCell(oxw, row(c).ToString, "str", 0)
                Next
                'Close out this row.
                oxw.WriteEndElement()
            Next
            'Close out the Worksheet and SheetData elements...
            oxw.WriteEndElement()
            oxw.WriteEndElement()
        End Using
        'Now we're going to create an OpenXMLWriter using the WorkbookPart (that we created above)...
        Using oxw As OpenXmlWriter = OpenXmlWriter.Create(wbp)
            'Add starting elements for the Workbook and Sheets collection.
            oxw.WriteStartElement(New Workbook())
            oxw.WriteStartElement(New Sheets())
            'Add the Sheet (name the Sheet after the file name minus the extension).
            oxw.WriteElement(New Sheet() With {.Name = Path.GetFileNameWithoutExtension(filename), .SheetId = 1, .Id = xls.WorkbookPart.GetIdOfPart(wsp)})
            'Write End elements for the Workbook/Sheets
            oxw.WriteEndElement()
            oxw.WriteEndElement()
        End Using
    End Using

End Sub

'This Sub is used to write a value to a Cell using OpenXMLWriter.
Private Sub WriteCell(ByRef oxw As OpenXmlWriter, value As String, datatype As String, style As UInt32Value)
    Dim oxa As New List(Of OpenXmlAttribute) From {New OpenXmlAttribute("t", Nothing, datatype), New OpenXmlAttribute("s", Nothing, style)}
    oxw.WriteStartElement(New Cell(), oxa)
    If value <> Nothing Then oxw.WriteElement(New CellValue(value))
    oxw.WriteEndElement()
End Sub

Em relação à resposta do tuncalik , que é ótima, especialmente se você quiser brincar um pouco com o código :) mas estou colocando minhas datas no Excel no formato americano, ou seja, 2 de março de 2014 no Reino Unido é 03/02/2014, mas nos EUA é 02/03/2014 com o primeiro mês, depois o dia da semana. Eu preciso ter no formato do Reino Unido, alguma idéia, por favor?

Eu verifiquei que ele está armazenado no formato do Reino Unido em minha DataTable e também que meu Excel está definido como Reino Unido, mas por alguma razão, quando ele cria o documento do Excel, ele pensa que é dos EUA (isso porque a Microsoft é uma empresa dos EUA :)

Vou tentar fazer experiências com códigos de cultura, mas não tenho certeza de onde colocá-los ainda. Tentei, mas não surtiu efeito.

ps

Eu tive que mudar uma linha para fazê-lo funcionar, adicionando um 'elenco' como abaixo

// single worksheet
Excel._Worksheet workSheet = (Excel._Worksheet)excelApp.ActiveSheet;

Atualização: eu consegui a formatação das datas no Reino Unido ao converter para o formato LongDateTime, mas é apenas uma solução alternativa.

DateTime startDate = Convert.ToDateTime(myList[0].ToString());
string strStartDate = startDate.ToLongDateString();
DateTime endDate = Convert.ToDateTime(myList[myListTotalRows].ToString());
string strEndDate = endDate.ToLongDateString();    

Felicidades.

Você pode usar o EasyXLS, que é uma biblioteca para exportar arquivos do Excel.

Verifique este código:

DataSet ds = new DataSet();
ds.Tables.Add(dataTable);

ExcelDocument xls = new ExcelDocument();
xls.easy_WriteXLSFile_FromDataSet("datatable.xls", ds, 
           new ExcelAutoFormat(Styles.AUTOFORMAT_EASYXLS1), "DataTable");

Veja também este exemplo sobre como exportar tabela de dados para o Excel em C # .

Tópico antigo - mas pensei em colocar meu código aqui. Eu escrevi uma pequena função para escrever uma tabela de dados em uma nova planilha do Excel em um caminho especificado (local). Além disso, você precisará adicionar uma referência à biblioteca do microsoft excel 14.0.

Eu puxei deste tópico sobre como escrever qualquer coisa para o Excel - como escrever alguns dados para o arquivo do Excel (.xlsx)

Eu usei isso para extrapolar como escrever uma tabela de dados

* observe que, nas declarações catch, tenho uma referência de classe estática de manipulador de erros (você pode ignorá-los)

 using excel = Microsoft.Office.Interop.Excel;
 using System.IO;
 using System.Data;
 using System.Runtime.InteropServices;

 //class and namespace wrapper is not shown in this example 

 private void WriteToExcel(System.Data.DataTable dt, string location)
    {
        //instantiate excel objects (application, workbook, worksheets)
        excel.Application XlObj = new excel.Application();
        XlObj.Visible = false;
        excel._Workbook WbObj = (excel.Workbook)(XlObj.Workbooks.Add(""));
        excel._Worksheet WsObj = (excel.Worksheet)WbObj.ActiveSheet;

        //run through datatable and assign cells to values of datatable
        try
        {
            int row = 1; int col = 1;
            foreach (DataColumn column in dt.Columns)
            {
                //adding columns
                WsObj.Cells[row, col] = column.ColumnName;
                col++;
            }
            //reset column and row variables
            col = 1;
            row++;
            for (int i = 0; i < dt.Rows.Count; i++)
            {
                //adding data
                foreach (var cell in dt.Rows[i].ItemArray)
                {
                    WsObj.Cells[row, col] = cell;
                    col++;
                }
                col = 1;
                row++;
            }
            WbObj.SaveAs(location);
        }
        catch (COMException x)
        {                
            ErrorHandler.Handle(x);
        }
        catch (Exception ex)
        {               
            ErrorHandler.Handle(ex);
        }
        finally
        {
            WbObj.Close();                
        }
    }

Uma maneira de fazer isso também seria com o ACE OLEDB Provider (consulte também strings de conexão para Excel ). Claro, você precisa ter o provedor instalado e registrado. Você deve tê-lo, se tiver o Excel instalado, mas isso é algo que deve ser considerado ao implantar o aplicativo.

Este é o exemplo de como chamar o método auxiliar de ExportHelper:ExportHelper.CreateXlsFromDataTable(myDataTable, @"C:\tmp\export.xls");

O auxiliar para exportar para arquivo Excel usando ACE OLEDB:

public class ExportHelper
{
    private const string ExcelOleDbConnectionStringTemplate = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source={0};Extended Properties=\"Excel 8.0;HDR=YES\";";

    /// <summary>
    /// Creates the Excel file from items in DataTable and writes them to specified output file.
    /// </summary>
    public static void CreateXlsFromDataTable(DataTable dataTable, string fullFilePath)
    {
        string createTableWithHeaderScript = GenerateCreateTableCommand(dataTable);

        using (var conn = new OleDbConnection(String.Format(ExcelOleDbConnectionStringTemplate, fullFilePath)))
        {
            if (conn.State != ConnectionState.Open)
            {
                conn.Open();
            }

            OleDbCommand cmd = new OleDbCommand(createTableWithHeaderScript, conn);
            cmd.ExecuteNonQuery();

            foreach (DataRow dataExportRow in dataTable.Rows)
            {
                AddNewRow(conn, dataExportRow);
            }
        }
    }

    private static void AddNewRow(OleDbConnection conn, DataRow dataRow)
    {
        string insertCmd = GenerateInsertRowCommand(dataRow);

        using (OleDbCommand cmd = new OleDbCommand(insertCmd, conn))
        {
            AddParametersWithValue(cmd, dataRow);
            cmd.ExecuteNonQuery();
        }
    }

    /// <summary>
    /// Generates the insert row command.
    /// </summary>
    private static string GenerateInsertRowCommand(DataRow dataRow)
    {
        var stringBuilder = new StringBuilder();
        var columns = dataRow.Table.Columns.Cast<DataColumn>().ToList();
        var columnNamesCommaSeparated = string.Join(",", columns.Select(x => x.Caption));
        var questionmarkCommaSeparated = string.Join(",", columns.Select(x => "?"));

        stringBuilder.AppendFormat("INSERT INTO [{0}] (", dataRow.Table.TableName);
        stringBuilder.Append(columnNamesCommaSeparated);
        stringBuilder.Append(") VALUES(");
        stringBuilder.Append(questionmarkCommaSeparated);
        stringBuilder.Append(")");
        return stringBuilder.ToString();
    }

    /// <summary>
    /// Adds the parameters with value.
    /// </summary>
    private static void AddParametersWithValue(OleDbCommand cmd, DataRow dataRow)
    {
        var paramNumber = 1;

        for (int i = 0; i <= dataRow.Table.Columns.Count - 1; i++)
        {
            if (!ReferenceEquals(dataRow.Table.Columns[i].DataType, typeof(int)) && !ReferenceEquals(dataRow.Table.Columns[i].DataType, typeof(decimal)))
            {
                cmd.Parameters.AddWithValue("@p" + paramNumber, dataRow[i].ToString().Replace("'", "''"));
            }
            else
            {
                object value = GetParameterValue(dataRow[i]);
                OleDbParameter parameter = cmd.Parameters.AddWithValue("@p" + paramNumber, value);
                if (value is decimal)
                {
                    parameter.OleDbType = OleDbType.Currency;
                }
            }

            paramNumber = paramNumber + 1;
        }
    }

    /// <summary>
    /// Gets the formatted value for the OleDbParameter.
    /// </summary>
    private static object GetParameterValue(object value)
    {
        if (value is string)
        {
            return value.ToString().Replace("'", "''");
        }
        return value;
    }

    private static string GenerateCreateTableCommand(DataTable tableDefination)
    {
        StringBuilder stringBuilder = new StringBuilder();
        bool firstcol = true;

        stringBuilder.AppendFormat("CREATE TABLE [{0}] (", tableDefination.TableName);

        foreach (DataColumn tableColumn in tableDefination.Columns)
        {
            if (!firstcol)
            {
                stringBuilder.Append(", ");
            }
            firstcol = false;

            string columnDataType = "CHAR(255)";

            switch (tableColumn.DataType.Name)
            {
                case "String":
                    columnDataType = "CHAR(255)";
                    break;
                case "Int32":
                    columnDataType = "INTEGER";
                    break;
                case "Decimal":
                    // Use currency instead of decimal because of bug described at 
                    // http://social.msdn.microsoft.com/Forums/vstudio/en-US/5d6248a5-ef00-4f46-be9d-853207656bcc/localization-trouble-with-oledbparameter-and-decimal?forum=csharpgeneral
                    columnDataType = "CURRENCY";
                    break;
            }

            stringBuilder.AppendFormat("{0} {1}", tableColumn.ColumnName, columnDataType);
        }
        stringBuilder.Append(")");

        return stringBuilder.ToString();
    }
}

use a seguinte classe

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data;
using excel = Microsoft.Office.Interop.Excel;
using EL = ExcelLibrary.SpreadSheet;
using System.Drawing;
using System.Collections;
using System.Runtime.InteropServices;
using System.Windows.Forms;


namespace _basic
{
public class ExcelProcesser
{
    public void WriteToExcel(System.Data.DataTable dt)
    {
        excel.Application XlObj = new excel.Application();
        XlObj.Visible = false;
        excel._Workbook WbObj = (excel.Workbook)(XlObj.Workbooks.Add(""));
        excel._Worksheet WsObj = (excel.Worksheet)WbObj.ActiveSheet;
        object misValue = System.Reflection.Missing.Value;


        try
        {
            int row = 1; int col = 1;
            foreach (DataColumn column in dt.Columns)
            {
                //adding columns
                WsObj.Cells[row, col] = column.ColumnName;
                col++;
            }
            //reset column and row variables
            col = 1;
            row++;
            for (int i = 0; i < dt.Rows.Count; i++)
            {
                //adding data
                foreach (var cell in dt.Rows[i].ItemArray)
                {
                    WsObj.Cells[row, col] = cell;
                    col++;
                }
                col = 1;
                row++;
            }
            WbObj.SaveAs(fileFullName, excel.XlFileFormat.xlWorkbookNormal, misValue, misValue, misValue, misValue, excel.XlSaveAsAccessMode.xlExclusive, misValue, misValue, misValue, misValue, misValue);
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }
        finally
        {
            WbObj.Close(true, misValue, misValue);
        }
    }
}

}

Esta solução é basicamente enviar List<Object>dados para o Excel, ele usa DataTable para fazer isso, eu implementei um método de extensão, então basicamente há duas coisas necessárias. 1. Um método de extensão.

public static class ReportHelper
{
    public static string ToExcel<T>(this IList<T> data)
    {
        PropertyDescriptorCollection properties =
            TypeDescriptor.GetProperties(typeof(T));
        DataTable table = new DataTable();
        foreach (PropertyDescriptor prop in properties)
        {
            //table.Columns.Add(prop.Name, Nullable.GetUnderlyingType(prop.PropertyType) ?? prop.PropertyType);
            if (prop.Attributes[typeof(FGMS.Entity.Extensions.ReportHeaderAttribute)] != null)
            {
                table.Columns.Add(GetColumnHeader(prop), Nullable.GetUnderlyingType(prop.PropertyType) ?? prop.PropertyType);
            }
        }

        //So it seems like when there is only one row of data the headers do not appear
        //so adding a dummy blank row which fixed the issues
        //Add a blank Row - Issue # 1471
        DataRow blankRow = table.NewRow();
        table.Rows.Add(blankRow);

        foreach (T item in data)
        {
            DataRow row = table.NewRow();
            foreach (PropertyDescriptor prop in properties)
                //row[prop.Name] = prop.GetValue(item) ?? DBNull.Value;
                if (prop.Attributes[typeof(FGMS.Entity.Extensions.ReportHeaderAttribute)] != null)
                {
                    row[GetColumnHeader(prop)] = prop.GetValue(item) ?? DBNull.Value;
                }
            table.Rows.Add(row);
        }
        table.TableName = "Results";
        var filePath = System.IO.Path.GetTempPath() + "\\" + System.Guid.NewGuid().ToString() + ".xls";
        table.WriteXml(filePath);

        return filePath;
    }

    private static string GetColumnHeader(PropertyDescriptor prop)
    {
        return ((FGMS.Entity.Extensions.ReportHeaderAttribute)(prop.Attributes[typeof(FGMS.Entity.Extensions.ReportHeaderAttribute)])).ReportHeaderText;
    }       
}

2. Decore suas classes DTO com o atributo [ReportHeaderAttribute("Column Name")]

public class UserDTO
    {
        public int Id { get; set; }
        public int SourceId { get; set; }
        public string SourceName { get; set; }

        [ReportHeaderAttribute("User Type")]
        public string UsereType { get; set; }

        [ReportHeaderAttribute("Address")]
        public string Address{ get; set; }

        [ReportHeaderAttribute("Age")]
        public int Age{ get; set; }

        public bool IsActive { get; set; }

        [ReportHeaderAttribute("Active")]
        public string IsActiveString
        {
            get
            {
                return IsActive ? "Yes" : "No";
            }
        }}

Tudo o que precisa ser uma coluna no Excel tem que ser decorado com [ReportHeaderAttribute("Column Name")]

Então simplesmente

Var userList = Service.GetUsers() //Returns List of UserDTO;
var excelFilePath = userList.ToExcel();

HttpResponseMessage result = new HttpResponseMessage(HttpStatusCode.OK);
            var stream = new FileStream(excelFilePath, FileMode.Open);
            result.Content = new StreamContent(stream);
            result.Content.Headers.ContentType =
                new MediaTypeHeaderValue("application/vnd.ms-excel");
            result.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment") { FileName = "UserList.xls" };

            return result;

Para exportar dados para o Excel, você pode usar a biblioteca ClosedXML.Report ( https://github.com/ClosedXML/ClosedXML.Report ). Acredite em mim, esta é uma biblioteca maravilhosa e fácil de usar. A biblioteca não precisa do Excel Interop. ClosedXML.Report gera um arquivo Excel baseado em um modelo que você pode criar no Excel usando qualquer formatação. Por exemplo:

    var template = new XLTemplate(@".\Templates\report.xlsx");

    using (var db = new DbDemos())
    {
        var cust = db.customers.LoadWith(c => c.Orders).First();
        template.AddVariable(cust);
        template.Generate();
    }

    template.SaveAs(outputFile);

Private tmr As System.Windows.Forms.Timer

Private Sub TestExcel() Handles Button1.Click

    '// Initial data: SQL Server table with 6 columns and 293000 rows.


    '// Data table holding all data
    Dim dt As New DataTable("F161")

    '// Create connection
    Dim conn As New SqlConnection("Server=MYSERVER;Database=Test;Trusted_Connection=Yes;")
    Dim fAdapter As New SqlDataAdapter With
    {
        .SelectCommand = New SqlCommand($"SELECT * FROM dbo.MyTable", conn)
    }

    '// Fill DataTable
    fAdapter.Fill(dt)

    '// Create Excel application
    Dim xlApp As New Excel.Application With {.Visible = True}

    '// Temporarily disable screen updating
    xlApp.ScreenUpdating = False

    '// Create brand new workbook
    Dim xlBook As Excel.Workbook = xlApp.Workbooks.Add()
    Dim xlSheet As Excel.Worksheet = DirectCast(xlBook.Sheets(1), Excel.Worksheet)

    '// Get number of rows
    Dim rows_count = dt.Rows.Count
    '// Get number of columns
    Dim cols_count = dt.Columns.Count

    '// Here 's the core idea: after receiving data
    '// you need to create an array and transfer it to sheet.
    '// Why array?
    '// Because it's the fastest way to transfer data to Excel's sheet.
    '// So, we have two tasks:
    '// 1) Create array
    '// 2) Transfer array to sheet

    '// =========================================================
    '// TASK 1: Create array
    '// =========================================================
    '// In order to create array, we need to know that
    '// Excel's Range object expects 2-D array whose lower bounds
    '// of both dimensions start from 1.
    '// This means you can't use C# array.
    '// You need to manually create such array.
    '// Since we already calculated number of rows and columns,
    '// we can use these numbers in creating array.
    Dim arr = Array.CreateInstance(GetType(Object), {rows_count, cols_count}, {1, 1})

    '// Fill array
    For r = 0 To rows_count - 1
        For c = 0 To cols_count - 1
            arr(r + 1, c + 1) = dt.Rows(r)(c)
        Next
    Next

    '// =========================================================
    '// TASK 2: Transfer array to sheet
    '// =========================================================
    '// Now we need to transfer array to sheet.
    '// So, how transfer array to sheet fast?
    '// 
    '// THE FASTEST WAY TO TRANSFER DATA TO SHEET IS TO ASSIGN ARRAY TO RANGE.
    '// We could, of course, hard-code values, but Resize property
    '// makes this work a breeze:
    xlSheet.Range("A1").Resize.Resize(rows_count, cols_count).Value = arr

    '// If we decide to dump data by iterating over array,
    '// it will take LOTS of time.
    '// For r = 1 To rows_count
    '//     For c = 1 To cols_count
    '//         xlSheet.Cells(r, c) = arr(r, c)
    '//     Next
    '// Next

    '// Here are time results:
    '// 1) Assigning array to Range: 3 seconds
    '// 2) Iterating over array: 45 minutes

    '// Turn updating on
    xlApp.ScreenUpdating = True
    xlApp = Nothing
    xlBook = Nothing
    xlSheet = Nothing

    '// Here we have another problem:
    '// creating array took lots of memory (about 150 MB).
    '// Using 'GC.Collect()', by unknown reason, doesn't help here.
    '// However, if you run GC.Collect() AFTER this procedure is finished
    '// (say, by pressing another button and calling another procedure),
    '// then the memory is cleaned up.
    '// I was wondering how to avoid creating some extra button to just release memory,
    '// so I came up with the idea to use timer to call GC.
    '// After 2 seconds GC collects all generations.
    '// Do not forget to dispose timer since we need it only once.

    tmr = New Timer()
    AddHandler tmr.Tick,
        Sub()
            GC.Collect()
            GC.WaitForPendingFinalizers()
            GC.WaitForFullGCComplete()
            tmr.Dispose()
        End Sub
    tmr.Interval = TimeSpan.FromSeconds(2).TotalMilliseconds()
    tmr.Start()

End Sub