reading from a text file at Button1_Click

 Hello,
i have the code
 
StreamReader sr=new StreamReader("C:\\users.txt");
string line;
protected void Page_Load(object sender, EventArgs e)
{

}

protected void Button1_Click(object sender, EventArgs e)
{
myBody.Attributes["onload"] = string.Empty;
if (TextBox1.Text == sr.ReadLine())
{
Label1.Text = TextBox1.Text;
return;
}
else
{
myBody.Attributes["onload"] = "alert('Us ...