'DataTalbe输出到TXT/CSV文件
Dim fs As FileStream = New FileStream(path, FileMode.Create, FileAccess.Write)
Dim sw As StreamWriter = New StreamWriter(fs, System.Text.Encoding.Default)
'列名
For i = 0 To dataDt.Columns.Count - 1
    data = data + dataDt.Columns(i).ColumnName.ToString
    If i < dataDt.Columns.Count - 1 Then
        data = data + "," 'CSV文件逗号分隔
    End If
Next

sw.WriteLine(data) '打印列名

'行数据
For i = 0 To dt.Rows.Count - 1
    data = ""
    For j = 0 To dt.Columns.Count - 1
        data = data + dt.Rows(i)(j).ToString.Trim  
        If j < dt.Columns.Count - 1 Then
            data = data + ","
        End If
    Next
    sw.WriteLine(data)
Next


'Format函数的使用
Dim no As Integer = 1
Dim res As String = Format(no, "000")  '打印为 "001",还可以使用小数点形式

'取字符串长度
System.Text.Encoding.Default.GetByteCount("字符串")