How to display an error message in an ASP.NET Web Application

Question

I have an ASP.NET web application, and I wanted to know how I could display an error message box when an exception is thrown.

For example,

    try
    {
        do something
    }
    catch 
    {
        messagebox.write("error"); 
        //[This isn't the correct syntax, just what I want to achieve]
    }

[The message box shows the error]

Thank you

Duplicate of How to display an error message box in a web application asp.net c#

Answer 1

Roughly you can do it like that :

try
{
    //do something
}
catch (Exception ex)
{
    string script = "<script>alert('" + ex.Message + "');</script>";
    if (!Page.IsStartupScriptRegistered("myErrorScript"))
    {
         Page.ClientScript.RegisterStartupScript("myErrorScript", script);
    }
}

But I recommend you to define your custom Exception and throw it anywhere you need. At your page catch this custom exception and register your message box script.