C#读写txt文件

using System.IO;
using System.Text.RegularExpressions;
DataSet myDs = new DataSet();
OpenFileDialog openFileDialog = new OpenFileDialog();
openFileDialog.InitialDirectory = "c://";//注意这里写路径时要用c://而不是c:/
openFileDialog.Filter = "txt文件|*.txt|所有文件|*.*";
openFileDialog.RestoreDirectory = true;
openFileDialog.FilterIndex = 1;
if (openFileDialog.ShowDialog() == DialogResult.OK)
{
int linNum = 0;
string[] txtline = File.ReadAllLines(openFileDialog.FileName, Encoding.GetEncoding("gb2312"));//读入中文不是乱码
linNum = txtline.Length;
jindu = "共:" + linNum.ToString() + "条";
for(int i=0;i<linNum;i++)
txtline[i] = Regex.Replace(txtline[i], @"/s", ""); //正则判断，去掉空格

System.Data.DataTable dt = new System.Data.DataTable("my_user");
dt.Columns.Add("F1", System.Type.GetType("System.Int32"));
dt.Columns.Add("F2", System.Type.GetType("System.String"));
dt.Columns.Add("F3", System.Type.GetType("System.String"));
dt.Columns.Add("F4", System.Type.GetType("System.String"));

myDs.Tables.Add(dt);
DataRow myRow;
myDs.Clear();

for (int i = 0; i < linNum; i++)
{
myRow = myDs.Tables["my_user"].NewRow();
for (int j = 1; j <= 4; j++)
{
if (j == 1)
{
string columnname = "F" + j.ToString();
myRow[columnname] = i;
}
else
{
char[] charSeparators = new char[] {','};
string[] row = txtline[i].Split(charSeparators, StringSplitOptions.None);//txt以“,”分割数据
string strValue = row[j - 2].Trim();
string columnname = "F" + j.ToString();
myRow[columnname] = strValue;
}
}
myDs.Tables["my_user"].Rows.Add(myRow);
}

using (StreamWriter sw = new StreamWriter("log.txt",true))
{
for (int i = 0; i < listBox1.Items.Count; i++)
{
sw.WriteLine(listBox1.Items[i].ToString());
}
}