[c#] How to export DataTable to Excel

Excel Interop:

This method prevents Dates getting flipped from dd-mm-yyyy to mm-dd-yyyy

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;
}

If you dont care about Dates being flipped, then use see link that shows how to populate all the cells in the Excel spreadsheet in one line of code:

Excel Interop - Efficiency and performance

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;
}