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Wednesday, August 22, 2007

String.Format- Exception of type System.Web.HttpUnhandledException was thrown.

Wednesday, August 22, 2007 9:43:12 PM (GMT Daylight Time, UTC+01:00)

Type
System.FormatException
Message
Exception of type 'System.Web.HttpUnhandledException' was thrown.
StackTrace
at System.Text.StringBuilder.FormatError()
at System.Text.StringBuilder.AppendFormat(IFormatProvider provider, String format, Object[] args)
at System.String.Format(IFormatProvider provider, String format, Object[] args)
Error Line
0

Just got that message (or at most "Exception of type 'System.Web.HttpUnhandledException' was thrown")? Puzzled? I was the first time I got it, I've been meaning to post about it for quite some time now so seeing as I got it again today I took the hint.

The error is horrifingly obvious when you know about it, in short, you've no doubt got some code that looks like this:

String.Format("<html><head><style type=\"text/css\">body{color: #fff;}</style><body>...");

Can you spot it now? Notice your style declaration is using the curly brackets? Basically String.Format is interpreting that as a placeholder i.e. {0} and is throwing a wobbly.

The solution is simple too, just replace all opening/closing brackets with two i.e:

String.Format("<html><head><style type=\"text/css\">body{{color: #fff;}}</style><body>...");

I hope that helps someone out there :)

P.S. Watch out for methods that use String.Format as they may catch you out in the same way -i.e. Subject of System.Net.Mail.MailMessage

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String.Format- Exception of type System.Web.HttpUnhandledException was thrown.

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Tags: ASP.Net | C# | The Site Doctor | Web Development | WebDD Tracked by:
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Tuesday, October 14, 2008 4:18:56 AM (GMT Daylight Time, UTC+01:00)

Can't you also escape the HTML-formatting string by adding an "@" character at the start, and then converting all quote characters to double-quotes?

String.Format(@"<html><head><style type=""text/css"">body{color: #fff;}</style><body>");

aspnyc

Tuesday, October 14, 2008 9:52:57 AM (GMT Daylight Time, UTC+01:00)

I've not tried doing it that way but I don't think so no because the curly braces still represent place holders for the replace (think {0}) which is what causes the issue in this case.

Will give it a go though.

Tim