用一行替换txt中的一行
/// <summary>
/// 替换txt中的某一行
/// </summary>
/// <param name="sFileName">文件路径+文件名</param>
/// <param name="first">代两个匹配参数，不需要的就删掉</param>
/// <param name="second">代两个匹配参数，不需要的就删掉</param>
/// <param name="newstr">新行的字符串</param>
public static void SaveTxtReplaceOneLine(string sFileName, string first, string second, string newstr)
{
StreamReader objReader = new StreamReader(sFileName);
string sLine = "";



string strall = "";
while (sLine != null)
{
sLine = objReader.ReadLine();
if (sLine != null && !sLine.Equals(""))
{
if (sLine.Contains(first+","+second))
strall += newstr+"\r\n";
else
strall += sLine+"\r\n";
}
}
objReader.Close();


FileStream fs = new FileStream(sFileName, FileMode.Create);
StreamWriter sw = new StreamWriter(fs);
//开始写入
sw.Write(strall);
//清空缓冲区
sw.Flush();
//关闭流
sw.Close();
fs.Close();
///MessageBox.Show("123");
}