document.write in StringBuilder?

I am using a StringBuilder in an ashx file to return javascript. It all works fine, except for one line...

javascript.Append("document.write(\"<script id=__ie_onload defer \" + \"src=javascript:void(0)><\/script>\");");

For readability, here is the unescaped version:

document.write("<script id=__ie_onload defer src=javascript:void(0)><\/script>");

If I comment out this line, my ashx file works like a charm! If I keep it in, though, it won't even run. Is there some sort of restriction on using a document.write statement in a S开发者_JS百科tringBuilder? Alternatively, is there a better way to write out Javascript from within .NET? It has to be from .NET due to the need for using server variables.

You have an unrecognized escape sequence in your closing script tag. \/ is not a valid escape sequence. You probably want:

javascript.Append("document.write(\"<script id=__ie_onload defer \" + \"src=javascript:void(0)></script>\");");

Or if you really want that \/ sequence, then doubly-escape the \:

javascript.Append("document.write(\"<script id=__ie_onload defer \" + \"src=javascript:void(0)><\\/script>\");");

As a debugging tip, if your tools provide you with such poor feedback that you can't even see compilation errors, try creating a test application containing the problematic code. I copied your code into a console application, something like:

static void Main(string[] args)
{
    var javascript = new StringBuilder();
    javascript.Append(...
    Console.Write(javascript);
}

...and I saw the problem immediately on compilation:

Unrecognized escape sequence

...with the problem sequence underlined.