C#写文件的一个小问题

Question

我用如下方式将一个DataTable写入一个TXT文件中，但重复点写入button,出现写入内容重复写入的问题，我需要的是写入一次就够了，但现在是追加写入，不知道是什么问题？
        private void TabWriteToTxt(DataTable tb, string fname) 
        {
            FileStream fs;
            StreamWriter sw;           
            try
            {
                fs = File.Create(fname);
                sw = new StreamWriter(fs);                string tmpstr = "";
                int cols = tb.Columns.Count;
                foreach (DataRow dr in tb.Rows)
                {
                    tmpstr = "";
                    for (int i = 0; i < cols; i++)
                    {
                        tmpstr += dr[i].ToString().Trim();
                        if ((i + 1) < cols) tmpstr += "\t";
                    }
                    sw.WriteLine(tmpstr);
                }
                sw.Close();
             
            }
            catch (Exception ex)
            {
                ShowErrorMessage("保存文件发生异常！" + ex.Message.ToString());
            }
        }

Answer 1

if(File.Exists(fname))
   File.Delete(fname);fs = File.Create(fname);
                sw = new StreamWriter(fs);                string tmpstr = ""; 

Answer 2

sw = new StreamWriter(fs); 改为: sw = new StreamWriter(fs,false);

Answer 3

StreamWriter writer = File.CreateText([Path]);

Answer 4

private void button1_Click(object sender, EventArgs e)
{
    DataTable dt = new DataTable();
    dt.Columns.Add("c1");
    dt.Columns.Add("c2");
    dt.Columns.Add("c3");
    dt.Rows.Add("1","1","1");
    dt.Rows.Add("2","2","2");
    dt.Rows.Add("3","3","3");    TabWriteToTxt(dt, "c:\\ls.txt");
}private void TabWriteToTxt(DataTable tb, string fname)
{
    StreamWriter sw;
    try
    {
        sw = new StreamWriter(fname, false);        string tmpstr = "";
        int cols = tb.Columns.Count;
        foreach (DataRow dr in tb.Rows)
        {
            tmpstr = "";
            for (int i = 0; i < cols; i++)
            {
                tmpstr += dr[i].ToString().Trim();
                if ((i + 1) < cols) tmpstr += "\t";
            }
            sw.WriteLine(tmpstr);
        }
        sw.Close();
    }
    catch (Exception ex)
    {
       // ShowErrorMessage("保存文件发生异常！" + ex.Message.ToString());
    }
}

Answer 5

if(File.Exists(fname)) 
  File.Delete(fname); fs = File.Create(fname); 
                sw = new StreamWriter(fs);                 string tmpstr = ""; 

Answer 6

        private void TabWriteToTxt(DataTable tb, string fname)
        {
            StringBuilder sb = new StringBuilder();
            foreach (DataRow row in tb.Rows)
            {
                for (int i = 0; i < tb.Columns.Count; i++)
                {
                    sb.AppendFormat("{0}{1}", row[i], i == tb.Columns.Count - 1 ? Environment.NewLine : "\t");
                }
            }
            File.WriteAllText(fname, sb.ToString());
        }