Display exception message through javascript alert in asp.net

Question

I am trying to show exception message through javascript alert box.

Here is the sample code.

public static void HandleException(Page page, Exception ex)
{
    string message = ex.Message.ToString();
    ScriptManager.RegisterClientScriptBlock(page, page.GetType(), "", "alert('"+message+"');", true);

}

It runs if i give literal values for the string variable. e.g.

string message = "Hello World";

But it fails if I give message = ex.Message;

Any Idea?

"But it fails if I give message = ex.Message;" Fails how? — T.J. Crowder
– T.J. Crowder, Commented Jun 23, 2011 at 6:42
I mean the alert box does not show up. It shows up only if message variable has literal string — rdp
– rdp, Commented Jun 23, 2011 at 6:44
I bet there's an error message somewhere. Check out the JavaScript console of the browser. — T.J. Crowder
– T.J. Crowder, Commented Jun 23, 2011 at 6:46

Darin Dimitrov · Accepted Answer · 2011-06-23 06:43:38Z

15

You need to encode it, for example using JavaScriptSerializer because if the message contains some escape characters like ' or " this will definitely break your javascript:

var message = new JavaScriptSerializer().Serialize(ex.Message.ToString());
var script = string.Format("alert({0});", message);
ScriptManager.RegisterClientScriptBlock(page, page.GetType(), "", script, true);

answered Jun 23, 2011 at 6:43

Darin Dimitrov

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1 Comment

TTT Over a year ago

I needed to modify a library function that returned the first line since the scripts were already being built on all the pages. I found trimming the quotes helpful since the Serialize adds enclosing quotes: new JavaScriptSerializer().Serialize(ex.Message.ToString()).Trim('"');

Akram Shahda · Accepted Answer · 2011-06-23 07:14:59Z

3

try    
{    
    //do some thing    
}    
catch (Exception ex)
{    
    Response.Write("<script language='javascript'>alert('" + 
        Server.HtmlEncode(ex.Message) + "')</script>");    
}

edited Jun 23, 2011 at 7:14

Akram Shahda

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answered Jun 23, 2011 at 6:51

Bibhu

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Comments

Akram Shahda · Accepted Answer · 2011-06-23 07:15:19Z

2

Does your ex.Message have any ' characters in it? They may need escaping.

edited Jun 23, 2011 at 7:15

Akram Shahda

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answered Jun 23, 2011 at 6:44

Paul McLean

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