source: Common/CsvExport.cs

using System;
using System.Text;
using System.IO;
using System.Windows.Forms;

namespace Common
{
    class CsvExport
    {
        public void ListViewToCsv(ListView listView, string filePath, bool includeHidden)
        {
            // Make header string
            StringBuilder result = new StringBuilder();
            WriteCsvRow(result, listView.Columns.Count, i => includeHidden || listView.Columns[i].Width > 0, i => listView.Columns[i].Text);

            // Export data rows
            foreach (ListViewItem listItem in listView.Items)
                WriteCsvRow(result, listView.Columns.Count, i => includeHidden || listView.Columns[i].Width > 0, i => listItem.SubItems[i].Text);

            File.WriteAllText(filePath, result.ToString());
        }

        public void DataGridViewToCsv(DataGridView dataGridView, string filePath, bool includeHidden)
        {
            // Make header string
            StringBuilder result = new StringBuilder();
            WriteCsvRow(result, dataGridView.Columns.Count, i => includeHidden || dataGridView.Columns[i].Width > 0, i => dataGridView.Columns[i].HeaderText);

            // Export data rows
            foreach (DataGridViewRow row in dataGridView.Rows)
                WriteCsvRow(result, row.Cells.Count, i => includeHidden || row.Cells[i].Size.Width > 0, i => row.Cells[i].Value.ToString());

            File.WriteAllText(filePath, result.ToString());
        }        

        private void WriteCsvRow(StringBuilder result, int itemsCount, Func<int, bool> isColumnNeeded, Func<int, string> columnValue)
        {
            bool isFirstTime = true;
            for (int i = 0; i < itemsCount; i++)
            {
                if (!isColumnNeeded(i))
                    continue;

                if (!isFirstTime)
                    result.Append(",");
                isFirstTime = false;

                result.Append(String.Format("\"{0}\"", columnValue(i).Replace("\"", "\"\"")));
            }
            result.AppendLine();
        }

    }
}