what does " <%: " do?

Question

I have seen the following tag as an answer to a question:

<%: Model.FirstName %>

what does " <%: " do?

Answer 1

It html encodes the output of Firstname, this prevents encoding attacks like cross-side scripting (XSS).

Html encoded:

<%: Model.FirstName %>

Normal output:

<%= Model.FirstName %>

More info can by found at this blog post:

New <%: %> Syntax for HTML Encoding Output in ASP.NET 4 (and ASP.NET MVC 2)

Answer 2

There is some useful information for this: http://weblogs.asp.net/scottgu/archive/2010/04/06/new-lt-gt-syntax-for-html-encoding-output-in-asp-net-4-and-asp-net-mvc-2.aspx