CODEWITHSUNDEEP
c#javascriptjqueryasp.netajax
Lamloumi Afif
Lamloumi Afif

Reputation: 9081

calling a javascript function && handling an event

I have an asp.net application in which i have to call a javascript function when an event is fired .I tried this :

protected Consultation controlconsultation  = new Consultation();
 protected void Page_Load(object sender, EventArgs e)
        {

           controlconsultation.imageinfo += controlconsultation_imageinfo;
           Session["controlconsultation"] = controlconsultation;
       }

        void controlconsultation_imageinfo(object sender, CommandEventArgs e)
        {String csName = "myScript";
            Type csType = this.GetType();

            // Get a ClientScriptManager reference from the Page class.
            ClientScriptManager cs = Page.ClientScript;

            // Check to see if the client script is already registered.
            if (!cs.IsClientScriptBlockRegistered(csType, csName))
            {
                StringBuilder csText = new StringBuilder();
                csText.Append("<script type=\"text/javascript\"> ");
                csText.Append("alert(" + "Espace_Candidat/InfoEdition.ascx" +"); </");
                csText.Append("script>");
                cs.RegisterClientScriptBlock(csType, csName, csText.ToString());
            }
        }

Code behind of the user control 

public event CommandEventHandler imageinfo ; 
protected void Page_Load(object sender, EventArgs e)
        {
 Consultation current = (Consultation)Session["controlconsultation"];
                imageinfo = current.imageinfo;
       }
  protected void Valider (object sender, CommandEventArgs e)
          {
            if (imageinfo != null)
              {
                  string pageNumber = (string)e.CommandArgument;
                  CommandEventArgs args = new CommandEventArgs("Control", pageNumber);
                  imageinfo(this, args);
              }
          }

I just need to display an alert message when the event is fired . When i launched the application i don't get any result but if i put the code of the event in the page load i will see the alert.

Upvotes: 0

Views: 321

Answers (4)

deostroll
deostroll

Reputation: 11975

The recommended pattern to solve this problem is a user control. You are correct on this count. However, you've to take care of wiring stuff properly.

You can look at the following article for a guideline: http://www.codeproject.com/Articles/51671/How-To-Expose-Events-from-UserControl

The steps in short are:

  1. You define a delegate
  2. Define an event on that user control using above delegate
  3. Write the necessary plumbing code in the user control code behind
  4. Take care of wiring the code in your aspx markup.

To highlight the 4th point, say its a dropdown inside your user control which contains a list of names. You've defined an event, say NameChanged as follows:

public event NameChangedHandler NameChanged;

In your aspx markup make sure your user control is defined as follows:

<uc1:FooControl runat="server" OnNameChanged="FooCallback"></uc1:FooControl>

Make note of the convention here; in the code behind you've declared event as NameChanged. In your markup, the letters On gets prefixed to it: hence OnNameChanged.

Edit:

Here is an example app; its the same as described above.

MyUserControl.ascx:

<%@ Control Language="C#" AutoEventWireup="true" CodeBehind="MyUserControl.ascx.cs" Inherits="WebApp.UserControlExample.MyUserControl" %>
<asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="true" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged">
    <asp:ListItem>Jim</asp:ListItem>
    <asp:ListItem>John</asp:ListItem>
    <asp:ListItem>Rosemary</asp:ListItem>
    <asp:ListItem>Catherine</asp:ListItem>
</asp:DropDownList>

MyUserControl.ascx.cs:

using System;

namespace WebApp.UserControlExample
{
    public delegate void NameChangedEventHandler(string name);
    public partial class MyUserControl : System.Web.UI.UserControl
    {
        public event NameChangedEventHandler NameChanged;
        protected void Page_Load(object sender, EventArgs e)
        {

        }

        protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
        {
            if (NameChanged != null)
                NameChanged(DropDownList1.SelectedValue);
        }
    }
}

Make note of how the "plumbing" is done. I've put AutoPostback="true" for the dropdownlist; hence I can handle its SelectedIndexChanged event in the code behind of the user control. This is where I can decide on my logic to raise an event.

WebForm1.aspx:

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="WebApp.UserControlExample.WebForm1" %>

<%@ Register src="MyUserControl.ascx" tagname="MyUserControl" tagprefix="uc1" %>

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <div>

    </div>
        <uc1:MyUserControl ID="MyUserControl1" runat="server" OnNameChanged="MyUserControl1_NameChanged" />
        <br />
        <asp:Label ID="Label1" runat="server" Text=""></asp:Label>
    </form>
</body>
</html>

WebForm1.aspx.cs:

using System;

namespace WebApp.UserControlExample
{
    public partial class WebForm1 : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

        }

        protected void MyUserControl1_NameChanged(string name)
        {
            Label1.Text = "Selected name is <b>" + name + "</b>";
            //you probably want to call your ClientScript.RegisterStartupScript in here...
        }
    }
}

Make note of the event callback on the target aspx webform.

Upvotes: 1

Afnan Ahmad
Afnan Ahmad

Reputation: 2542

Try this: 

ScriptManager.RegisterStartupScript(this.Page, Page.GetType(), "error", "alert('Hello');", true);

Upvotes: 0

Cros
Cros

Reputation: 4377

Try using:

cs.RegisterStartupScript

Upvotes: 0

Vishal
Vishal

Reputation: 51

Script tag should end properly. Check for end script tag...

Upvotes: 0

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