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问题:

I have a web application (ASP.Net 3.5) with a conventional 3 layer design. If the user clicks a button a postback happens, some middle and data layer code runs, and the screen is refreshed. If the user clicks the button multiple times before the first postback is completed my logic gets confused and the app can end up in an invalid state. What are the best ways to prevent this?

I can use javascript to disable the button but this just hides the problem. How do I build my business and data layers to handle this?

回答1:

The three most popular methods (which are often used in tandem) are:

Disable submit buttons once clicked/pressed;
Use POST+REDIRECT+GET to avoid back button issues; and
Replace history in the browser so you can't go back (but this should be used sparingly and with good reason).

回答2:

If I was to be brutally honest, I would say that it sounds like you're the one confused about web postbacks, not your application (that's if you're the one who wrote it). ;-)

That said, in addition to other suggestions, what I would do in this case is place a "token" in hidden field in the form - like a GUID - that is posted back. Use this to track the work being done and only allow it to be used once. E.g. when posted back, place it in session storage. Each time a postback is performed check the session first for this token, and if it is there then do nothing. If it's NOT there, store it in session and do the work. When the session ends, tokens are thrown away automagically. Easy. Much better than some convoluted database token.

Oisin

回答3:

Do disable submit button once clicked. This will prevent accidental double-click or more
I usually redirect to a different URL after postback to avoid accidental/intentional page refresh.
Finally in your DB insert method, check for identical data inserted within certain time frame (probably in seconds) before doing the insert. If duplicate data is found inserted within just seconds (or minutes. whatever makes most sense in your situation), show warning message and have user hit submit again if user feels it is not error. (This method makes most sense when you have user account and user is submitting data when logged in, so duplicate data check is done for the user.)

回答4:

Check out this ASP.NET AJAX control called PostBack Ritalin from a fellow SO'r Dave Ward.

回答5:

I have solved the problem writing a javascript disabling the click function button:

MyButton.Attributes.Add("onclick",
    "javascript:this.onclick=function(){return false;};");

回答6:

We have all seen the websites that disable "submit" buttons when you click on them. This is often done to prevent users from clicking the button multiple times. Normally this is accomplished using an 'onclick' JavaScript event to disable the button. In ASP.NET, each server side item already has a onclick event handler which calls the server back for event processing. To accomplish the same thing in ASP.NET, you could easily do:

btnSubmit.Attributes.Add("onclick", "this.disabled=true;" + GetPostBackEventReference(btnSubmit).ToString());

Where 'btnSubmit' is the name of the button in question. What happens here is we create an onclick event that does two things. Firstly, it disables the button in the users browser. The second thing it does is submit the normal postback event to the server.

回答7:

Even i got the Same Problem I have resolved like Below.

After uploading a File If you Redirect to same page or some other page in your project this problem will be avoided.

For Example:

In My ASPX

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm.aspx.cs" Inherits="WebApplication.WebForm" %>

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>

<body>
    <form id="form1" runat="server">
        <div>
            <asp:FileUpload ID="FileUpload1" runat="server" />
            <asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="Button" />
        </div>
    </form>
</body>
</html>

Even i got the Same Problem I have resolved like Below.

After uploading the File If you Redirect to same page or some other page in your project. After Redirection Response will not be there once you redirected.

In My ASPX

In My Code Behind

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

        }

        protected void Button1_Click(object sender, EventArgs e)
        {
            string path = Server.MapPath("~");
            path = path + FileUpload1.FileName;
            FileUpload1.SaveAs(path);
            Response.Redirect("WebForm.aspx"); // Responce will be cleared. This Redirection will do the Trick 
            //Put the debugger and check it will work
        }
    }