JavaScript: Alert.Show(message) From ASP.NET Code-behind

Question

I am reading this JavaScript: Alert.Show(message) From ASP.NET Code-behind

I am trying to implement the same. So I created a static class like this:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Data;
using System.Data.SqlClient;
using System.Web;
using System.Text;
using System.Web.UI;

namespace Registration.DataAccess
{
    public static class Repository
    {
        /// <summary> 
        /// Shows a client-side JavaScript alert in the browser. 
        /// </summary> 
        /// <param name="message">The message to appear in the alert.</param> 
        public static void Show(string message) 
            { 
               // Cleans the message to allow single quotation marks 
               string cleanMessage = message.Replace("'", "\'"); 
               string script = "<script type="text/javascript">alert('" + cleanMessage + "');</script>"; 

               // Gets the executing web page 
               Page page = HttpContext.Current.CurrentHandler as Page; 

               // Checks if the handler is a Page and that the script isn't allready on the Page 
               if (page != null && !page.ClientScript.IsClientScriptBlockRegistered("alert")) 
               { 
                 page.ClientScript.RegisterClientScriptBlock(typeof(Alert), "alert", script); 
               } 
            } 
    }
}

On this line:

string script = "<script type="text/javascript">alert('" + cleanMessage + "');</script>";

It is showing me the error: ; Expected

And also on

page.ClientScript.RegisterClientScriptBlock(typeof(Alert), "alert", script);

Err: The type or namespace name 'Alert' could not be found (are you missing a using directive or an assembly reference?)

What am I doing wrong here?

Brian Webster · Accepted Answer · 2012-09-23 05:34:57Z

130

Here is an easy way:

Response.Write("<script>alert('Hello');</script>");

edited Sep 23, 2012 at 5:34

Brian Webster

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answered Apr 29, 2011 at 4:38

Muhammad Akhtar

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1 Comment

Jack Spektor Over a year ago

I don't like this way. You'll never know where your code will be inserted, because it's inserted into stream. Also it potentially could break HTML and cause Javascript errors. RegisterClientScriptBlock is right way to run Javascript on client.

cem · Accepted Answer · 2011-04-28 21:45:45Z

24

string script = string.Format("alert('{0}');", cleanMessage);
if (page != null && !page.ClientScript.IsClientScriptBlockRegistered("alert")) 
{
    page.ClientScript.RegisterClientScriptBlock(page.GetType(), "alert", script, true /* addScriptTags */);
}

answered Apr 28, 2011 at 21:45

cem

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Comments

user2561316 · Accepted Answer · 2013-09-21 09:16:58Z

19

This message show the alert message directly

ScriptManager.RegisterStartupScript(this,GetType(),"showalert","alert('Only alert Message');",true);

This message show alert message from JavaScript function

ScriptManager.RegisterStartupScript(this, GetType(), "displayalertmessage", "Showalert();", true);

These are two ways to display alert messages in c# code behind

answered Sep 21, 2013 at 9:16

user2561316

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Comments

Andrusho · Accepted Answer · 2013-07-10 17:52:20Z

10

if you are using ScriptManager on the page then you can also try using this:

System.Web.UI.ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "AlertBox", "alert('Your Message');", true);

answered Jul 10, 2013 at 17:52

Andrusho

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2 Comments

Fandango68 Over a year ago

This works, but only if the page is static and not redirected (see my answer elsewhere). If you have a Response.Redirect() after this to reload the page for example, the message does not display. There needs to be a forced wait until user presses OK or something.

Zeek2 Over a year ago

Yes, we use code v. similar to the above, mostly it works for us, but in some code it just doesn't work, possibly for the reason described by @Fandango68, above.

Xtian11 · Accepted Answer · 2017-08-18 01:04:15Z

Try this method:

public static void Show(string message) 
{                
    string cleanMessage = message.Replace("'", "\'");                               
    Page page = HttpContext.Current.CurrentHandler as Page; 
    string script = string.Format("alert('{0}');", cleanMessage);
    if (page != null && !page.ClientScript.IsClientScriptBlockRegistered("alert")) 
    {
        page.ClientScript.RegisterClientScriptBlock(page.GetType(), "alert", script, true /* addScriptTags */);
    } 
}

In Vb.Net

Public Sub Show(message As String)
    Dim cleanMessage As String = message.Replace("'", "\'")
    Dim page As Page = HttpContext.Current.CurrentHandler
    Dim script As String = String.Format("alert('{0}');", cleanMessage)
    If (page IsNot Nothing And Not page.ClientScript.IsClientScriptBlockRegistered("alert")) Then
        page.ClientScript.RegisterClientScriptBlock(page.GetType(), "alert", script, True) ' /* addScriptTags */
    End If
End Sub

Tejs · Accepted Answer · 2011-04-28 21:22:30Z

4

Your code does not compile. The string you have terminates unexpectedly;

string script = "<script type=";

That's effectively what you've written. You need to escape your double quotes:

string script = "<script type=\"text/javascript\">alert('" + cleanMessage + "');</script>";

This kind of thing should be painfully obvious since your source code coloring should be completely jacked.

answered Apr 28, 2011 at 21:22

Tejs

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6 Comments

Adriano Carneiro Over a year ago

Come on @Tejs, give a break :) Third question in a row that you arrive a few seconds earlier :)

RG-3 Over a year ago

Thanks! What about the Alert err?

Tejs Over a year ago

It's probably a side effect of the jacked code. Impossible to say without fixing the earlier bug.

RG-3 Over a year ago

Thanks Tejs. But I am not getting any alert mesg from the above code.

Andreas Over a year ago

What does the browser (firebug, developer tools, dragonfly, ...) say? Any error messages on the script tabs?

|

gbs · Accepted Answer · 2011-04-28 23:16:57Z

4

There could be more than one reasons for not working.

1: Are you calling your function properly? i.e.

Repository.Show("Your alert message");

2: Try using RegisterStartUpScript method instead of scriptblock.

3: If you are using UpdatePanel, that could be an issue as well.

Check this(topic 3.2)

answered Apr 28, 2011 at 23:16

gbs

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Comments

Ahmad lahham · Accepted Answer · 2016-07-19 07:25:15Z

4

ClientScript.RegisterStartupScript(Page.GetType(), "validation", "<script language='javascript'>alert('ID Exists ')</script>");

answered Jul 19, 2016 at 7:25

Ahmad lahham

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1 Comment

Frits Over a year ago

Please try to avoid just dumping a code as an answer and try to explain what it does and why. Your code might not be obvious for people who do not have the relevant coding experience.

Waldir Leoncio · Accepted Answer · 2013-10-07 20:13:17Z

3

And i think, the line:

string cleanMessage = message.Replace("'", "\'");

does not work, it must be:

string cleanMessage = message.Replace("'", "\\\'");

You need to mask the \ with a \ and the ' with another \.

edited Oct 7, 2013 at 20:13

Waldir Leoncio

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answered Oct 7, 2013 at 19:51

Kirsten

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Comments

Orlando Herrera · Accepted Answer · 2014-03-19 21:11:29Z

3

Calling a JavaScript function from code behind

Step 1 Add your Javascript code

<script type="text/javascript" language="javascript">
    function Func() {
        alert("hello!")
    }
</script>

Step 2 Add 1 Script Manager in your webForm and Add 1 button too

Step 3 Add this code in your button click event

ScriptManager.RegisterStartupScript(this.Page, Page.GetType(), "text", "Func()", true);

answered Mar 19, 2014 at 21:11

Orlando Herrera

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Comments

Soner Gönül · Accepted Answer · 2015-01-08 12:16:40Z

3

Try this if you want to display the alert box to appear on the same page, without displaying on a blank page.

ScriptManager.RegisterStartupScript(this, GetType(), "showalert", "alert('Sorry there are no attachments');", true);

edited Jan 8, 2015 at 12:16

Soner Gönül

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answered Dec 3, 2014 at 12:12

jithin john

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Comments

R Kitty · Accepted Answer · 2011-04-28 21:22:29Z

2

The quotes around type="text/javascript" are ending your string before you want to. Use single quotes inside to avoid this problem.

Use this

 type='text/javascript'

answered Apr 28, 2011 at 21:22

R Kitty

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Comments

Adriano Carneiro · Accepted Answer · 2011-04-28 21:37:22Z

2

You need to fix this line:

string script = "<script type=\"text/javascript\">alert('" + cleanMessage + "');</script>";

And also this one:

RegisterClientScriptBlock("alert", script); //lose the typeof thing

edited Apr 28, 2011 at 21:37

answered Apr 28, 2011 at 21:23

Adriano Carneiro

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4 Comments

RG-3 Over a year ago

Thanks! What about the Alert err?

RG-3 Over a year ago

Thanks Andrian. But I am not getting any alert mesg from the above code.

Adriano Carneiro Over a year ago

You should fix one thing at a time. Does this error still happens after you fix the string?

RG-3 Over a year ago

Nops! The err is gone. Build is a success but it is not showing me any kind of alert mesg..

Nick Kahn · Accepted Answer · 2012-04-23 02:55:18Z

2

string script = string.Format("alert('{0}');", cleanMessage);     
ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "key_name", script );", true);

edited Apr 23, 2012 at 2:55

answered Apr 23, 2012 at 2:41

Nick Kahn

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Comments

ZGski · Accepted Answer · 2016-05-26 20:07:32Z

2

Works 100% without any problem and will not redirect to another page...I tried just copying this and changing your message

// Initialize a string and write Your message it will work
string message = "Helloq World";
System.Text.StringBuilder sb = new System.Text.StringBuilder();
sb.Append("alert('");
sb.Append(message);
sb.Append("');");
ClientScript.RegisterOnSubmitStatement(this.GetType(), "alert", sb.ToString());

edited May 26, 2016 at 20:07

ZGski

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answered May 26, 2016 at 19:24

Attaullah Khan

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Comments

Carlos M · Accepted Answer · 2011-04-28 21:25:13Z

1

try:

string script = "<script type=\"text/javascript\">alert('" + cleanMessage + "');</script>";

answered Apr 28, 2011 at 21:25

Carlos M

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Comments

Community · Accepted Answer · 2017-05-23 12:34:37Z

1

You can use this method after sending the client-side code as a string parameter.

NOTE: I didn't come up with this solution, but I came across it when I was searching for a way to do so myself, I only edited it a little.

It is very simple and helpful, and can use it to perform more than 1 line of javascript/jquery/...etc or any client-side code

private void MessageBox(string msg)
{
    Label lbl = new Label();
    lbl.Text = "<script language='javascript'>" + msg + "')</script>";
    Page.Controls.Add(lbl);
}

source: https://stackoverflow.com/a/9365713/824068

edited May 23, 2017 at 12:34

CommunityBot

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answered Oct 31, 2012 at 15:16

MA9H

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1 Comment

Hugh Seagraves Over a year ago

I think there were some pieces missing. "<script language='javascript'>alert('" + msg + "');</script>"

Jack Spektor · Accepted Answer · 2012-11-26 13:08:07Z

1

string script = "<script type="text/javascript">alert('" + cleanMessage + "');</script>";

You should use string.Format in this case. This is better coding style. For you it would be:

string script = string.Format(@"<script type='text/javascript'>alert('{0}');</script>");

Also note that when you should escape " symbol or use apostroph instead.

answered Nov 26, 2012 at 13:08

Jack Spektor

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Comments

Silvio Marino · Accepted Answer · 2013-05-24 11:41:03Z

1

private void MessageBox(string msg)
{
    Label lbl = new Label();
    lbl.Text  = string.Format(@"<script type='text/javascript'>alert('{0}');</script>",msg);
    Page.Controls.Add(lbl);
}

answered May 24, 2013 at 11:41

Silvio Marino

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Comments

blex · Accepted Answer · 2015-02-27 18:00:39Z

1

You need to escape your quotes (Take a look at the "Special characters" section). You can do it by adding a slash before them:

string script = "<script type=\"text/javascript\">alert('" + cleanMessage + "');</script>";
  Response.Write(script);

edited Feb 27, 2015 at 18:00

blex

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answered Feb 27, 2015 at 14:18

user2389005

Comments

Fandango68 · Accepted Answer · 2015-09-08 02:06:38Z

I use this and it works, as long as the page is not redirect afterwards. Would be nice to have it show, and wait until the user clicks OK, regardless of redirects.

/// <summary>
/// A JavaScript alert class
/// </summary>
public static class webMessageBox
{

/// <summary>
/// Shows a client-side JavaScript alert in the browser.
/// </summary>
/// <param name="message">The message to appear in the alert.</param>
    public static void Show(string message)
    {
       // Cleans the message to allow single quotation marks
       string cleanMessage = message.Replace("'", "\\'");
       string wsScript = "<script type=\"text/javascript\">alert('" + cleanMessage + "');</script>";

       // Gets the executing web page
       Page page = HttpContext.Current.CurrentHandler as Page;

       // Checks if the handler is a Page and that the script isn't allready on the Page
       if (page != null && !page.ClientScript.IsClientScriptBlockRegistered("alert"))
       {
           //ClientScript.RegisterStartupScript(this.GetType(), "MessageBox", wsScript, true);
           page.ClientScript.RegisterClientScriptBlock(typeof(webMessageBox), "alert", wsScript, false);
       }
    }    
}

Edwin b · Accepted Answer · 2016-07-27 09:00:58Z

1

Calling script only can not do that if the event is PAGE LOAD event specially.

you need to call, Response.Write(script);

so as above, string script = "alert('" + cleanMessage + "');"; Response.Write(script);

will work in at least for a page load event for sure.

answered Jul 27, 2016 at 9:00

Edwin b

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2 Comments

Edwin b Over a year ago

Sample code 1:string close = @"<script type='text/javascript'> window.returnValue = true; window.close(); </script>"; base.Response.Write(close);

Edwin b Over a year ago

sample code 2:string close = @"<script type='text/javascript'> alert('This is my alert'); </script>"; base.Response.Write(close);

Deepak Kushwaha · Accepted Answer · 2017-01-23 05:17:07Z

1

if u Want To massage on your code behind file then try this

string popupScript = "<script language=JavaScript>";
popupScript += "alert('Your Massage');";

popupScript += "</";
popupScript += "script>";
Page.RegisterStartupScript("PopupScript", popupScript);

answered Jan 23, 2017 at 5:17

Deepak Kushwaha

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Tabish Usman · Accepted Answer · 2017-01-23 05:25:05Z

1

you can use following code.

 StringBuilder strScript = new StringBuilder();
 strScript.Append("alert('your Message goes here');");
 Page.ClientScript.RegisterStartupScript(this.GetType(),"Script", strScript.ToString(), true);

answered Jan 23, 2017 at 5:25

Tabish Usman

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Code · Accepted Answer · 2019-05-25 05:16:26Z

0

 <!--Java Script to hide alert message after few second -->
    <script type="text/javascript">
        function HideLabel() {
            var seconds = 5;
            setTimeout(function () {
                document.getElementById("<%=divStatusMsg.ClientID %>").style.display = "none";
            }, seconds * 1000);
        };
    </script>
    <!--Java Script to hide alert message after few second -->

answered May 25, 2019 at 5:16

Code

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Soner Gönül · Accepted Answer · 2015-01-08 12:16:27Z

-3

its simple to call a message box, so if you want to code behind or call function, I think it is better or may be not. There is a process, you can just use namespace

using system.widows.forms;

then, where you want to show a message box, just call it as simple, as in C#, like:

messagebox.show("Welcome");

edited Jan 8, 2015 at 12:16

Soner Gönül

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answered Aug 20, 2013 at 20:54

Mustafa Iqbal

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2 Comments

Andrew Barber Over a year ago

The question is about showing a message on the client - with Javascript

Zeek2 Over a year ago

If only in were so :^/

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