如何在asp.net中的页面加载事件之前调用javascript确认对话框？

Question

This is my server side code:

 protected void Page_Load(object sender, EventArgs e)
    {

       if (Page.IsPostBack == false)
       {

               string confirmValue = Request.Form["confirm_value"];
               if (confirmValue == "Yes")
                {
                UserId = Convert.ToInt32(Request.QueryString["UserId"]);
                ProgramSrNno =          Convert.ToInt32(Request.QueryString["ProgramSrNo"]);
                UpdateAcknowledment(UserId, ProgramSrNno);
            }
        }
   }

This is my javascript code:

window.onload = Confirm();

function Confirm() {
       var confirm_value = document.createElement("INPUT");
       confirm_value.type = "hidden";
        confirm_value.name = "confirm_value";
        if (confirm("Do you want to Acknowledge?")) {
            confirm_value.value = "Yes";
        } else {
            confirm_value.value = "No";
        }
        document.forms["frmAcknowledgement"].appendChild(confirm_value);

    }

i want dialog box should come first then accordingly code behind pageload event work. if user has selected ok then pageload code should work else not. but here first my code behind pageload event is running then it is going to javascript code.

Answer 1

Please check this one

protected void Page_Init(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
            Page.ClientScript.RegisterStartupScript(this.GetType(), "Confirm", "if(confirm('Are you sure?')){alert('ok');}else{alert('cancel');}", true);
        }
    }

Answer 2

You can't.

PageLoad is handled at the server, a javascript confirm() is executed on the client after the pageload has been executed.

But you can let the javascript post back to the server again. If you put a hiddenfield control in the page and set its value in your javascript, you can retrieve the value of the field during postback

markup

<asp:HiddenField ID="hidField" ClientIDMode="Static" runat="server" />

JS

function Confirm() {
    if (confirm("Do you want to Acknowledge?")) {
        document.getElementById('hidField').value = "Yes";
    } else {
        document.getElementById('hidField').value = "No";
    }
    document.forms[0].submit();
}

codebehind

if(Page.IsPostBack) 
{
    string confirmValue = this.hidField.Value;
}