データテーブル（配列）からCSVファイルに保存する方法

データテーブル（配列）からCSVファイルに保存する方法
VB.NET

Public Sub ConvertDataTableToCsv( _
        dt As DataTable, csvPath As String, writeHeader As Boolean)
    Dim enc As System.Text.Encoding = _
        System.Text.Encoding.GetEncoding("Shift_JIS")

    Dim sr As New System.IO.StreamWriter(csvPath, False, enc)

    Dim colCount As Integer = dt.Columns.Count
    Dim lastColIndex As Integer = colCount - 1
    Dim i As Integer

    If writeHeader Then
        For i = 0 To colCount - 1
            Dim field As String = dt.Columns(i).Caption
            field = EncloseDoubleQuotesIfNeed(field)
            sr.Write(field)
            If lastColIndex > i Then
                sr.Write(","c)
            End If
        Next
        sr.Write(vbCrLf)
    End If

    Dim row As DataRow
    For Each row In dt.Rows
        For i = 0 To colCount - 1
            Dim field As String = row(i).ToString()
            field = EncloseDoubleQuotesIfNeed(field)
            sr.Write(field)
            If lastColIndex > i Then
                sr.Write(","c)
            End If
        Next
        sr.Write(vbCrLf)
    Next

    sr.Close()
End Sub

Private Function EncloseDoubleQuotesIfNeed(field As String) As String
    If NeedEncloseDoubleQuotes(field) Then
        Return EncloseDoubleQuotes(field)
    End If
    Return field
End Function

Private Function EncloseDoubleQuotes(field As String) As String
    If field.IndexOf(""""c) > -1 Then
        field = field.Replace("""", """""")
    End If
    Return """" & field & """"
End Function

Private Function NeedEncloseDoubleQuotes(field As String) As Boolean
    Return field.IndexOf(""""c) > -1 OrElse _
        field.IndexOf(","c) > -1 OrElse _
        field.IndexOf(ControlChars.Cr) > -1 OrElse _
        field.IndexOf(ControlChars.Lf) > -1 OrElse _
        field.StartsWith(" ") OrElse _
        field.StartsWith(vbTab) OrElse _
        field.EndsWith(" ") OrElse _
        field.EndsWith(vbTab)
End Function

C#

public void ConvertDataTableToCsv(
    DataTable dt, string csvPath, bool writeHeader)
{
    System.Text.Encoding enc =
        System.Text.Encoding.GetEncoding("Shift_JIS");

    System.IO.StreamWriter sr =
        new System.IO.StreamWriter(csvPath, false, enc);

    int colCount = dt.Columns.Count;
    int lastColIndex = colCount - 1;

    if (writeHeader)
    {
        for (int i = 0; i < colCount; i++)
        {
            string field = dt.Columns[i].Caption;
            field = EncloseDoubleQuotesIfNeed(field);
            sr.Write(field);
            if (lastColIndex > i)
            {
                sr.Write(',');
            }
        }
        sr.Write("\r\n");
    }

    foreach (DataRow row in dt.Rows)
    {
        for (int i = 0; i < colCount; i++)
        {
            string field = row[i].ToString();
            field = EncloseDoubleQuotesIfNeed(field);
            sr.Write(field);
            if (lastColIndex > i)
            {
                sr.Write(',');
            }
        }
        sr.Write("\r\n");
    }

    sr.Close();
}

private string EncloseDoubleQuotesIfNeed(string field)
{
    if (NeedEncloseDoubleQuotes(field))
    {
        return EncloseDoubleQuotes(field);
    }
    return field;
}

private string EncloseDoubleQuotes(string field)
{
    if (field.IndexOf('"') > -1)
    {
        field = field.Replace("\"", "\"\"");
    }
    return "\"" + field + "\"";
}

private bool NeedEncloseDoubleQuotes(string field)
{
    return field.IndexOf('"') > -1 ||
        field.IndexOf(',') > -1 ||
        field.IndexOf('\r') > -1 ||
        field.IndexOf('\n') > -1 ||
        field.StartsWith(" ") ||
        field.StartsWith("\t") ||
        field.EndsWith(" ") ||
        field.EndsWith("\t");
}