Exporting data to a CSV, tab delimited or other text format

A question that often comes up in forums is how to export data to a CSV file, or other text format. Here's a method that takes data from a DataReader and writes it to a file.


using System;
using System.Data;
using System.Data.OleDb;
using System.IO;
using System.Text;
using System.Web;

public static void WriteToTextFile(string separator, string filename)
  string ConnStr = "Provider=Microsoft.Jet.OleDb.4.0;" +
				"Data Source=|DataDirectory|Northwind.mdb;";
  string query = "SELECT * FROM Customers";
  string sep = separator;

  StreamWriter sw = new StreamWriter(HttpContext.Current.Server.MapPath(filename));
  using (OleDbConnection Conn = new OleDbConnection(ConnStr))
    using (OleDbCommand Cmd = new OleDbCommand(query, Conn))
      using (OleDbDataReader dr = Cmd.ExecuteReader())
        int fields = dr.FieldCount - 1;
        while (dr.Read())
          StringBuilder sb = new StringBuilder();
          for (int i = 0; i <= fields; i++)
            if (i != fields)
              sep = sep;
              sep = "";
            sb.Append(dr[i].ToString() + sep);


Imports System
Imports System.Data
Imports System.Data.OleDb
Imports System.IO
Imports System.Text
Imports System.Web

Public Shared Sub WriteToTextFile(ByVal separator As String, ByVal filename As String)
  Dim ConnStr As String = "Provider=Microsoft.Jet.OleDb.4.0;" + 
          "Data Source=|DataDirectory|Northwind.mdb;"
  Dim query As String = "SELECT * FROM Customers"
  Dim sep As String = separator

  Dim sw As New StreamWriter(HttpContext.Current.Server.MapPath(filename))
  Using Conn As New OleDbConnection(ConnStr)
    Using Cmd As New OleDbCommand(query, Conn)
      Using dr As OleDbDataReader = Cmd.ExecuteReader()
        Dim fields As Integer = dr.FieldCount - 1
        While dr.Read()
          Dim sb As New StringBuilder()
          Dim i As Integer = 0
          While i <= fields
            If i <> fields Then
              sep = sep
              sep = ""
            End If
            sb.Append(dr(i).ToString() + sep)
            i += 1
          End While
        End While
      End Using
    End Using
  End Using
End Sub

And in both cases, the method is called by simply passing the separator and filename in as strings:

WriteToTextFile(",", "vfile.txt")