CODEWITHSUNDEEP
asp.netpostbackrefresh
jmpena
jmpena

Reputation: 65

Prevent Page Refresh in C#

Duplicate of Asp.Net Button Event on refresh fires again??? GUID?

hello, ive a website and when a user click a button and the page postback, if the user refresh the Page or hit F5 the button method is called again.

any one know some method to prevent page refresh with out redirect the page to the same page again ?

something like if (page.isRefresh) or something... or if exist any javascript solution is better.

this seen to works.... but when i refresh it does not postback but show the before value in the textbox

http://www.dotnetspider.com/resources/4040-IsPageRefresh-ASP-NET.aspx

private Boolean IsPageRefresh = false;
protected void Page_Load(object sender, EventArgs e)
{        
    if (!IsPostBack)
    {
        ViewState["postids"] = System.Guid.NewGuid().ToString();
        Session["postid"] = ViewState["postids"].ToString();
        TextBox1.Text = "Hi";

    }
    else
    {
        if (ViewState["postids"].ToString() != Session["postid"].ToString())
        {
            IsPageRefresh = true;
        }
        Session["postid"] = System.Guid.NewGuid().ToString();
        ViewState["postids"] = Session["postid"];
    }
}
protected void Button1_Click(object sender, EventArgs e)
{
    if (!IsPageRefresh) // check that page is not refreshed by browser.
    {
        TextBox2.Text = TextBox1.Text + "@";

    }
}

Upvotes: 5

Views: 39622

Answers (5)

Jorge Loreto
Jorge Loreto

Reputation: 11

I tried many ways and I ended up looking for the form data sent when the postback / refresh is triggered... I found that there is a Key for any VIEWSTATE created and you can just compare those Keys like...

I put that on my custom basepage to reuse it like an Property

public bool IsPageRefresh = false;
protected void Page_Init(object sender, EventArgs e)
{
     if (IsPostBack)
     {
          var rForm = Request.Form;
          var vw = rForm["__EVENTVALIDATION"].ToString();
          var svw = Session["__EVENTVALIDATION"] ?? "";
          if (vw.Equals(svw)) IsPageRefresh = true;
               Session["__EVENTVALIDATION"] = vw;
     }
}

Upvotes: 1

laertespl
laertespl

Reputation: 51

     bool IsPageRefresh ;

 if (Page.IsPostBack)
    {
        if (ViewState["postid"].ToString() != Session["postid"].ToString())
            IsPageRefresh = true;
    }
    Session["postid"] = System.Guid.NewGuid().ToString();
    ViewState["postid"] = Session["postid"];

Upvotes: 1

Saber
Saber

Reputation: 2648

Thanks for comments and sorry for my mistake, I found this code in: http://www.codeproject.com/KB/aspnet/Detecting_Refresh.aspx And this time tested ;)

    private bool _refreshState;
    private bool _isRefresh;

    protected override void LoadViewState(object savedState)
    {
        object[] AllStates = (object[])savedState;
        base.LoadViewState(AllStates[0]);
        _refreshState = bool.Parse(AllStates[1].ToString());
        _isRefresh = _refreshState == bool.Parse(Session["__ISREFRESH"].ToString());
    }

    protected override object SaveViewState()
    {
        Session["__ISREFRESH"] = _refreshState;
        object[] AllStates = new object[2];
        AllStates[0] = base.SaveViewState();
        AllStates[1] = !(_refreshState);
        return AllStates;
    }

    protected void btn_Click(object sender, EventArgs e)
    {
        if (!_isRefresh)
            Response.Write(DateTime.Now.Millisecond.ToString());
    }

Upvotes: 8

André Hedberg
André Hedberg

Reputation: 11

This doesn't solve the problem.

First of all, storing a token in the view state is not a good idea, since it can be disabled. Use control state instead. Although, a HttpModule is a better solution.

All in all, this will not work anyway. If you open another tab/window the session will be invalid for the previous tab/window. Therefore braking it. You must somehow store a unique value each time a page is first loaded. Use that to determine where the request came from and then check the "refresh ticket". As you may see, the object for one user might get pretty big depending on the amount of requests made, where and how long you store this information.

I haven't seen any solution to this I'm afraid, as it is pretty complex.

Upvotes: 1

John Lewin
John Lewin

Reputation: 6230

You can test for the Page.IsPostBack property to see if the page is responding to an initial request or if it's handling a PostBack such as your button click event. Here's a bit more information: w3schools on IsPostBack

Unfortunately that's not going to solve your problem since IsPostBack will be true when the user clicks the button as well as when they refresh the page after the button action has taken place.

If you're doing a task like performing CRUD on some data, you can Response.Redirect the user back to the same page when you're done processing and get around this problem. It has the side benefit of reloading your content (assuming you added a record to the DB it would now show in the page...) and prevents the refresh problem behavior. The only caveat is they still resubmit the form by going back in their history.

Postbacks were a bad implementation choice for the Asp.net and generally are what ruin the Webforms platform for me.

Upvotes: 4

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