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Answer 1

+2 A:

If you want the browser address bar to show the updated URL you can allow the button click to postback to the server and then you handle the TextChanged event of the textbox.

In the TextChanged event handler you build the new URL with the changed querystring arguments and use Response.Redirect to redirect the browser to the new URL.

Here is a quick an dirty example.

Given a ASPX page with a textbox and a button, somthing like this

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="WebApplication1._Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"&gt;
<html xmlns="http://www.w3.org/1999/xhtml"&gt;
<head runat="server">
  <title></title>
</head>
<body>

  <script type="text/javascript">
    function requery() {
      var query = location.search.substring(1);
      var pairs = query.split("&");
      var param1Value = document.getElementById("txtParam1").value;

      url = "/Default.aspx?param1=" + param1Value;
      for (var i = 0; i < pairs.length; ++i) {
        var pair = pairs[i];
        if ((pair.indexOf("param1") != 0) && (pair.length > 0)) {
          url += "&" + pair;
        }
      }
      location.href = url;
    }
  </script>

  <form id="form1" runat="server">
  <div>
    <asp:TextBox ID="txtParam1" runat="server" OnTextChanged="txtParam1_TextChanged"></asp:TextBox>
    <asp:Button ID="Button1" runat="server" Text="Submit" />
    <input type="button" value="Client Action" onclick="requery()" />
  </div>
  </form>
</body>
</html>

Your code behind to handle the TextChanged event of the textbox could do the following.

using System;
using System.Text;

namespace WebApplication1
{
  public partial class _Default : System.Web.UI.Page
  {
    protected void Page_Load(object sender, EventArgs e)
    {
      if (!IsPostBack)
      {
        txtParam1.Text = Request.QueryString["param1"];
      }
    }

    protected void txtParam1_TextChanged(object sender, EventArgs e)
    {
      // Build the new URL with the changed value of TextBox1      
      StringBuilder url = new StringBuilder();
      url.AppendFormat("{0}?param1={1}",
        Request.Path, txtParam1.Text);

      // Append all the querystring values that where not param1 to the
      // new URL
      foreach (string key in Request.QueryString.AllKeys)
      {
        if (string.Compare(key, "param1", true) != 0)
        {
          url.AppendFormat("&{0}={1}", key, Request.QueryString[key]);
        }
      }

      // Redirect the browser to request the new URL
      Response.Redirect(url.ToString());
    }
  }
}

Chris Taylor 2010-07-24 07:21:09

Another issue I find is that, when enter string into text input, and submit again, Page_Load will be called twice, once with IsPostBack true and the other time with IsPostBack false, is that expected behavior (client send two request to server?)? Thank you.

George2 2010-07-24 08:06:33

@George2, what do you mean by keep the original two parameters. The sample I provided should keep param2 and param3 on the URL. As for the two Page_Load events, that is expected. The first is in response to the PostBack event of the button and the second is in response to the browser redirecting to the new URL (this is a GET so IsPostBack == false), which is the same target page with the new parameters.

Chris Taylor 2010-07-24 08:27:54

Yes, you are correct. I am wrong. :-(Could you answer this question please -- "Another issue I find is that, when enter string into text input, and submit again, Page_Load will be called twice, once with IsPostBack true and the other time with IsPostBack false, is that expected behavior (client send two request to server?)? Thank you."

George2 2010-07-24 08:31:19

@George2, I believe I already answered that in my first comment. I quote "As for the two Page_Load events, that is expected. The first is in response to the PostBack event of the button and the second is in response to the browser redirecting to the new URL (this is a GET so IsPostBack == false), which is the same target page with the new parameters"

Chris Taylor 2010-07-24 09:33:38

Thanks Chris, so in your sample code the default.aspx page is requested twice (from user click submit new entered text, to the page response with new entered text value in both url parameter/html text input)? Any better solutions which requests only once to server and it could achieve the same effect?

George2 2010-07-24 14:29:50

@George2, well an alternative would be to use javascript on the client side to build the new URL on the button click (this would be handled on a client side event rather than a server side event) and then change the Window.Location to the new URL. Take a look here for more info on Window.Location: http://www.w3schools.com/jsref/met_loc_replace.asp

Chris Taylor 2010-07-24 15:20:06

Thanks Chris, I read through the document as you suggested. But how to use window.location in your sample? Appreciate if you could provide some sample code or solutions. (I understand what is the function of window.location, but do not know how to utilize it in the problem I am facing). I am also confused that if I need to use javascript, should I user server side submit button (which uses "runat server") or html submit button?

George2 2010-07-25 14:04:40

@George2, I will try get sometime to put together a sample. But you would not use a serverside control for the button, since you want to handle this client side.

Chris Taylor 2010-07-25 15:19:25

@George2, I updated the ASPX code with a quick and dirty javascript function and a client button that calls that function. So you now have a simple example of how to do this on both the client and the server side. The JS can probably be improved, this is not exactly something I work with much so I just used the basic functions, but it should work.

Chris Taylor 2010-07-25 15:44:37

Thank you so much Chris! When I come to office, I will definitely try your solution and let you know the result here. Eager to try and learn from you guru!

George2 2010-07-25 17:57:56

Thanks, your solution works!

George2 2010-07-26 15:54:45

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