HtmlString vs. MvcHtmlString

HtmlString vs. MvcHtmlString

What are the differences bettween those two, or when to prefer one over the other?

Edit:

One thing to prefer MvcHtmlString over HtmlString is the extension method IsNullOrEmpty of MvcHtmlString.

HtmlString only exists in ASP.NET 4.

MvcHtmlString was a compatibility shim added to MVC 2 to support both .NET 3.5 and .NET 4. Now that MVC 3 is .NET 4 only, it's a fairly trivial subclass of HtmlString presumably for MVC 2->3 for source compatibility.

If you're ever going to drop back to MVC 2 it might make sense to use IHtmlString or var for values returned from MVC functions. Alternatively I think you can now just switch to HtmlString throughout.

HtmlString was only introduced in .Net 4.0.

In ASP.Net 3.5 MVC 2.0, you should use MvcHtmlString.
In .Net 4.0, you should use HtmlString. (which is simpler)

MvcHtmlString is used to indicate when a string should not be re-encoded.

See What is an MvcHtmlString and when should I use it?

and

What does <%: %> do in ASP.NET (MVC2)?