页面刷新问题（F5）

Question

I have a page on which i have only one TextBox say Comments and Post Comment Button.

Now during input user write something in Comments textbox and press Post Comment button. Whatever is written in the textbox all get stored in database and i clear the textbox with

textbox.text = string.empty statement.

After this user press F5 without doing anything and the same comment which i have already cleared gets stored in the database again. I want to keep track of this thing that when button event is fired on F5 should not do anything. please help in this.

Answer 1

Make sure you're doing the database insert on an event handler for the Post Comment button. If you're doing it in Page_Load , or some other method that's called by the framework on every rendering of the page, then this would result in the duplicate inserts you're seeing.

Answer 2

You may want to read up on the Post/Redirect/Get Pattern .

After performing the database submission you need to send a redirect back to the user which causes the browser to make a second request and eliminates the possibility of a duplicate post back if they refresh the browser. The redirect URL can be the same page you started on which you noted is one of the requirements.

Answer 3

插入数据库后，重定向到另一个页面。

Answer 4

This is a browser's issue. You click on your button and save data into DB in your button's handler but when you is clicking F5 after, browser asks you (not all browsers is asking): do you want to send same postback? You say Yes and browser sends same postback with same information to server. Server checks this postback and does Post Comment action where you save info into DB again.

Answer 5

There are some examples with source code how you detect refresh of the page to avoid double submition

http://www.codeproject.com/KB/aspnet/DetectingRefresh_.aspx

http://dotnetslackers.com/community/blogs/simoneb/archive/2007/01/06/Using-an-HttpModule-to-detect-page-refresh.aspx

Answer 6

Most simple solution (after Redirect) is using Session variable to count number of "post backs":

int postBackCount = (Session["postbacks"] == null) ? 0 : (int)Session["postbacks"];
if (Page.IsPostBack) {
    if (postBackCount >= 1) {
        lbError.Text = "Can't submit this more than once, sorry";
    }
    else {
        //do DB stuff here.....
    }
    Session["postbacks"] = postBackCount + 1;
}
else {
    Session["postbacks"] = 0;
}