访问文件时，这个问题如何解决，谢谢各位啦！
下面这段代码老是提醒说
编译器错误信息: CS0165: 使用了未赋值的局部变量“sw”
源错误:

行 42: finally
行 43: {
行 44: sw.Close();
行 45: }
行 46: }

大家帮忙给看看，先谢啦！

protected void Button1_Click(object sender, EventArgs e)
{
StreamWriter sw;
string filePath = Server.MapPath("text.txt");
try
{
if (File.Exists(filePath))
{
sw = File.AppendText(filePath);
}
else
{
sw = File.CreateText(filePath);
}
sw.WriteLine("Name:" + TextBox1.Text.Trim());
sw.WriteLine("Sex:" + TextBox2.Text.Trim());
sw.WriteLine("Age:" + TextBox3.Text.Trim());
sw.WriteLine("---------------------------");
Label1.Text = "信息保存成功!";
}
catch (Exception ex)
{
Label1.Text = "信息保存失败!";
}
finally
{
sw.Close();
}
}


[解决办法]
不用那么麻烦，这样就可以了：
string filePath = Server.MapPath("text.txt");
StreamWriter sw = new StreamWriter(filePath, false);
try
{
sw.WriteLine("Name:" + TextBox1.Text.Trim());
sw.WriteLine("Sex:" + TextBox2.Text.Trim());
sw.WriteLine("Age:" + TextBox3.Text.Trim());
sw.WriteLine("---------------------------");
Label1.Text = "信息保存成功!";
}
catch (Exception ex)
{
Label1.Text = "信息保存失败!";
}
finally
{
sw.Close();
}
[解决办法]

C# code

protected void Button1_Click(object sender, EventArgs e){  string filePath = Server.MapPath("text.txt");  using (StreamWriter sw = File.AppendText(filePath))  {    try    {      sw.WriteLine("Name:" + TextBox1.Text.Trim());      sw.WriteLine("Sex:"  + TextBox2.Text.Trim());      sw.WriteLine("Age:"  + TextBox3.Text.Trim());      sw.WriteLine("---------------------------");      Label1.Text = "信息保存成功!";    }    catch (Exception ex)    {      Label1.Text = "信息保存失败!";    }  }}
[解决办法]
1楼的一样没有赋值。2楼的可以使用！
[解决办法]
1楼，你测过吗？我测了一下你的好像不行哦
   protected void Button2_Click(object sender, EventArgs e)
   {
       string filePath = Server.MapPath("text.txt");
       StreamWriter sw;
       if (File.Exists(filePath))
       {
           sw = File.AppendText(filePath);
       }
       else
       {
           sw = File.CreateText(filePath);
       }

       try
       {
           sw.WriteLine("Name:" + TextBox1.Text.Trim());
           sw.WriteLine("Sex:" + TextBox2.Text.Trim());
           sw.WriteLine("Age:" + TextBox3.Text.Trim());  
           sw.WriteLine("---------------------------");
           Label1.Text = "信息保存成功!";
       }
       catch
       {
           Label1.Text = "信息保存失败!";
       }
       finally
       {
           sw.Close();
       }
   }

ps:使用时需要在web.config文件中的<system.web>加入<identity impersonate="true"/>提升修改权限 
 
对路径"......"的访问被拒绝--解决办法参考：http://www.cnblogs.com/zgqys1980/archive/2006/12/28/605877.html
[解决办法]
改为LS的是最好的解决办法，没必要手动去关闭它，用一个using就可以了