I am currently working with a small class that uses Javascript to display alerts. The situation is this: I have implemented this class on a page where users must input valid zip codes. If an invalid zip code is entered, an alert is shown and the user is redirected back to correct it. However, if a valid zip code is entered, they are redirected to another page. The issue arises when users click the back button on their browser; the alert is displayed regardless of the validity of the zip code.
Here is the sequence:
Zip entry page -> Enter Zip -> Check Zip
If a valid zip is entered, go to overview.aspx. If not, return to the zip entry page.
On overview.aspx, if the user clicks the back button, the alert pops up. This behavior is not desired. Below is the well-functioning code for the alert class, followed by the code that checks and displays the alert upon clicking the LinkButton.
protected void GotoReview(object sender, EventArgs e) {
if (ValidateZipCode(ZipCode)) {
Response.Redirect(string.Format("~/checkout/overview.aspx?pc={0}&zc={1}",
ProductCode, ZipCode));
}
else {
Alert.Show("The entered zip code is invalid. Please ensure the zip code is a valid zip code.");
}
}
private bool ValidateZipCode(string zip) {
if (zip.Length < 5 || zip.Length > 5) {
return false;
}
if (!Regex.IsMatch(zip, @"^(\d{5}-\d{4})|(\d{5})$")) {
return false;
}
return true;
}
public static class Alert {
public static void Show(string message) {
string cleanMessage = message.Replace("'", "\\'");
string script = "<script type=\"text/javascript\">alert('" + cleanMessage + "');</script>";
Page page = HttpContext.Current.CurrentHandler as Page;
if (page != null && !page.ClientScript.IsClientScriptBlockRegistered("alert")) {
page.ClientScript.RegisterClientScriptBlock(typeof(Alert), "alert", script);
}
}
}