使用asp.net的Javascript警报

Question

I want to bring up a js alert box on asp.net button click. The code i have is

 String jscript = @"<script language = 'javascript'> alert('This is my title');</script>";
 ClientScript.RegisterStartupScript(GetType(), "_jscript", jscript);

it works fine, but I want to have some more js popups later for some validation, where I assume I have to write the same code, but unfortunately it does not load rest of the popups on the same page.

Is this to do with update panels?

The control I am validating is

if (dp_menu.SelectedIndex > 0)
{
   //continue program
}
else
{
  //show popup
  //this pop p doesn't show up at all?
  String jscript = @"<script language = 'javascript'> alert('Another popup');</script>";
  ClientScript.RegisterStartupScript(GetType(), "_jscript", jscript);

}

Answer 1

Take a look at the specification for RegisterStartupScript , specifically the Remarks section:

A client script is uniquely identified by its key and its type. Scripts with the same key and type are considered duplicates. Only one script with a given type and key pair can be registered with the page. Attempting to register a script that is already registered does not create a duplicate of the script.

If you're passing in the same type via GetType() and the same key, "_jscript" , every time, then only the first call will result in any <script> being rendered. This is by design.

Poor Fix : Replace your unchanging key "_jscript" with a different key for each validation you perform, eg "_valNameIsBlank" , "_valNoItemSpecified" .

Better Fix : Avoid annoying your users with multiple validation popups by:

• Compiling a List<string> of all your validation failures
• After all your checks, see if you have any items in the list
• If so, concatenate them into a single validation failure message and display that in a single alert.

Answer 2

i would give you some thing more effective,
costume control

1. create new class library (Library_name)

add this class to library

using System.Text;
using System.Web.UI;
using System.ComponentModel;

namespace ClientSide
{
    [DefaultProperty("Text"),
    ToolboxData("<{0}:MessageBox runat=server>" 
        + "</{0}:MessageBox>")]
    public class MessageBox : System.Web.UI.Control 
    {
        private string text="";
        [Bindable(true),
        Category("Appearance"),
        DefaultValue("")]
        public string Text
        {
            get {return text;}
            set {text = value;}
        }

        protected override void Render(HtmlTextWriter output)
        {
            if (text.Length>0)
            {
                StringBuilder sb = new StringBuilder();
                sb.Append("<script language='javascript'>");
                sb.Append("alert('"+text+"')");
                sb.Append("</script>");
                output.Write(sb.ToString());
            }
        }
    }
}

to use it you have to register the control in the top of aspx page

<%@ Register TagPrefix="cc1" Namespace="ClientSide" Assembly="Library_Name" %>

3- then you can use it like this way in the aspx page

<cc1:MessageBox id="MessageBox1" runat="server" Text="popup Message"></cc1:MessageBox>

Answer 3

In RegisterStartupScript Keyvalues should be different for each script

Try different KeyValues instead of using "_jscript" in all script.