.NET CsvWriter

Imports System.Text
Imports System.IO

''' <summary>
''' 快速写入数据到CSV文件
''' </summary>
Public Class CsvWriter

#Region "Constants"
    ''' <summary>
    ''' Defines the default delimiter character separating each field.
    ''' </summary>
    Public Const DefaultDelimiter As Char = ","c

    ''' <summary>
    ''' Defines the default quote character wrapping every field.
    ''' </summary>
    Public Const DefaultQuote As Char = """"c

    ''' <summary>
    ''' Defines the default escape character letting insert quotation characters inside a quoted field.
    ''' </summary>
    Public Const DefaultEscape As Char = """"c

    ''' <summary>
    ''' Defines the default comment character indicating that a line is commented out.
    ''' </summary>
    Public Const DefaultComment As Char = "#"c
#End Region

#Region "Constructors"
    Sub New()
        Me.New(DefaultDelimiter, DefaultQuote, DefaultEscape, DefaultComment)
    End Sub

    Sub New(ByVal delimiter As Char)
        Me.New(delimiter, DefaultQuote, DefaultEscape, DefaultComment)
    End Sub

    ''' <summary>
    ''' Initializes a new instance of the CsvWriter class.
    ''' </summary>
    ''' <param name="delimiter">The delimiter character separating each field (default is ',').(分隔符号默认",")</param>
    ''' <param name="quote">The quotation character wrapping every field (default is ''').(需要转义的字符串 重复出现2次)</param>
    ''' <param name="escape">
    ''' The escape character letting insert quotation characters inside a quoted field (default is '\').
    ''' If no escape character, set to '\0' to gain some performance.(包装用)
    ''' </param>
    ''' <param name="comment">The comment character indicating that a line is commented out (default is '#').</param>
    ''' <exception cref="T:ArgumentNullException">
    '''		<paramref name="reader"/> is a <see langword="null"/>.
    ''' </exception>
    ''' <exception cref="ArgumentOutOfRangeException">
    '''		<paramref name="bufferSize"/> must be 1 or more.
    ''' </exception>
    Sub New(ByVal delimiter As Char, ByVal quote As Char, ByVal escape As Char, ByVal comment As Char)
        _delimiter = delimiter
        _quote = quote
        _escape = escape
        _comment = comment
    End Sub
#End Region

#Region "Write"
    Public Sub Write(ByVal writer As TextWriter, ByVal table As DataTable)
        Dim cols = From c As DataColumn In table.Columns Select ObjToString(c.ColumnName)
        writer.WriteLine(String.Join(_delimiter, cols))
        Write(writer, table.Rows)
    End Sub

    Public Sub Write(ByVal writer As TextWriter, ByVal rows As IList(Of String()))
        For Each row In rows
            Dim items() As String = (From r In row Select ObjToString(r)).ToArray
            Dim str As String = String.Join(_delimiter, items)
            writer.WriteLine(str)
        Next
    End Sub

    Public Sub Write(ByVal writer As TextWriter, ByVal rows() As DataRow)
        For Each row As DataRow In rows
            Dim items() As String = (From o As Object In row.ItemArray Select ObjToString(o)).ToArray
            Dim str As String = String.Join(_delimiter, items)
            writer.WriteLine(str)
        Next
    End Sub

    Public Sub Write(ByVal writer As TextWriter, ByVal rows As DataRowCollection)
        For Each row As DataRow In rows
            Dim items() As String = (From o As Object In row.ItemArray Select ObjToString(o)).ToArray
            Dim str As String = String.Join(_delimiter, items)
            writer.WriteLine(str)
        Next
    End Sub

    Public Function ObjToString(ByVal obj As Object) As String
        If obj Is Nothing Then Return String.Empty
        Dim str As String = obj.ToString
        'If str.Length > 30000 Then MsgBox(str)
        If str.Contains(_delimiter) OrElse str.Contains(_quote) OrElse str.Contains(vbCr) OrElse str.Contains(vbLf) Then
            Dim strb As New StringBuilder(_escape)
            For Each c In str
                If c = _quote Then strb.Append(_quote)
                strb.Append(c)
            Next
            strb.Append(_escape)
            Return strb.ToString
        End If
        Return str
    End Function
#End Region

#Region "Fields"
    ''' <summary>
    ''' Contains the <see cref="T:TextReader"/> export to the CSV file.
    ''' </summary>
    Private _writer As TextWriter

    ''' <summary>
    ''' Contains the comment character indicating that a line is commented out.
    ''' </summary>
    Private _comment As Char

    ''' <summary>
    ''' Contains the escape character letting insert quotation characters inside a quoted field.
    ''' </summary>
    Private _escape As Char

    ''' <summary>
    ''' Contains the delimiter character separating each field.
    ''' </summary>
    Private _delimiter As Char

    ''' <summary>
    ''' Contains the quotation character wrapping every field.
    ''' </summary>
    Private _quote As Char

    ''' <summary>
    ''' Indicates if the reader supports multiline.
    ''' </summary>
    Private _supportsMultiline As Boolean

    ''' <summary>
    ''' Indicates if the reader will skip empty lines.
    ''' </summary>
    Private _skipEmptyLines As Boolean
#End Region

#Region "Properties"
    ''' <summary>
    ''' Gets the comment character indicating that a line is commented out.
    ''' </summary>
    ''' <value>The comment character indicating that a line is commented out.</value>
    Public ReadOnly Property Comment As Char
        Get
            Return _comment
        End Get
    End Property

    ''' <summary>
    ''' Gets the escape character letting insert quotation characters inside a quoted field.
    ''' </summary>
    ''' <value>The escape character letting insert quotation characters inside a quoted field.</value>
    Public ReadOnly Property Escape As Char
        Get
            Return _escape
        End Get
    End Property

    ''' <summary>
    ''' Gets the delimiter character separating each field.
    ''' </summary>
    ''' <value>The delimiter character separating each field.</value>
    Public ReadOnly Property Delimiter As Char
        Get
            Return _delimiter
        End Get
    End Property

    ''' <summary>
    ''' Gets the quotation character wrapping every field.
    ''' </summary>
    ''' <value>The quotation character wrapping every field.</value>
    Public ReadOnly Property Quote As Char
        Get
            Return _quote
        End Get
    End Property
#End Region

End Class

using System;
using System.Collections.Generic;
using System.Text;
using System.IO;

namespace CsvIO.Csv
{
    /// <summary>
    /// 快速写入数据到CSV文件
    /// </summary>
    public static class CsvWriter
    {
        #region Constants

        /// <summary>
        /// Defines the default delimiter character separating each field.
        /// </summary>
        public const char DefaultDelimiter = ',';


        /// <summary>
        /// Defines the default quote character wrapping every field.
        /// </summary>
        public const char DefaultQuote = '"';

        /// <summary>
        /// Defines the default escape character letting insert quotation characters inside a quoted field.
        /// </summary>
        public const char DefaultEscape = '"';

        /// <summary>
        /// The space character.
        /// </summary>
        private const char SPACE = ' ';

        /// <summary>
        /// The carriage return character. Escape code is <c>\r</c>.
        /// </summary>
        private const char CR = (char)0x0d;

        /// <summary>
        /// The line-feed character. Escape code is <c>\n</c>.
        /// </summary>
        private const char LF = (char)0x0a;

        #endregion

        #region Write

        public static void Write(TextWriter writer, IEnumerable<string> row)
        {
            Write(writer, row, DefaultDelimiter);
        }

        public static void Write(TextWriter writer, IEnumerable<string> row, char delimiter)
        {
            bool start = false;
            foreach (string str in row)
            {
                if (start == true)
                    writer.Write(delimiter);
                else
                    start = true;
                writer.Write(CsvString(str, delimiter));
            }
            writer.WriteLine();
        }

        private static string CsvString(string str, char delimiter)
        {
            if (string.IsNullOrEmpty(str)) return string.Empty;
            bool delimit = false;

            StringBuilder sb = new StringBuilder();

            foreach (char c in str)
            {
                if (c == delimiter || c == CR || c == LF)
                {
                    delimit = true;
                }
                else if (c == DefaultQuote)
                {
                    sb.Append(DefaultQuote);
                    delimit = true;
                }
                sb.Append(c);
            }

            if (delimit)
            {
                sb.Insert(0, DefaultEscape);
                sb.Append(DefaultEscape);
            }
            return sb.ToString();
        }

        #endregion
    }
}