asp.net向文本文件(txt)指定行(第n行)插入数据

效果：比如在第4行后面插入“我是阿会楠”，则结果为：

1
2
3
4
我是阿会楠
5
6
7
8
9
目录下必须有“7.txt"这个文本文件，另外其实现方法可能不是最好的，大家看代码如果有新的方法，记得告诉我哦！

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;

using System.IO;
using System.Text;

public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{

string Path = Server.MapPath("7.txt");
string str = "我是阿会楠";
insertStr(Path,str,4);

}

public void insertStr(string Path,string str,int n)
{
string strLineStart = "";
string strLineEnd = "";
string strLineEnd2 = "";
string strLine = "";

try
{
//实例化一个StreamReader对象,并申明编码为GB2312
StreamReader sr = new StreamReader(Path, Encoding.GetEncoding("GB2312"));

//读取插入前的数据
for (int i = 0; i < n; i++)
{
strLineStart += sr.ReadLine() + "/r/n";

}

//后面的数据
while (strLineEnd != null)
{
strLineEnd = sr.ReadLine();
strLineEnd2 += strLineEnd + "/r/n";
}

strLine = strLineStart + str + "/r/n" + strLineEnd2;

//关闭
sr.Dispose();
sr.Close();

StreamWriter sw = new StreamWriter(Path, false, Encoding.GetEncoding("GB2312"));
sw.WriteLine(strLine);

//关闭
sw.Flush();
sw.Dispose();
sw.Close();

}
catch
{
}

}

}