I think you are attacking it from the wrong angle by trying to encode all posted data.
Note that a "<" could also come from other outside sources, like a database field, a configuration, a file, a feed and so on.
Furthermore, "<" is not inherently dangerous. It's only dangerous in a specific context: when writing strings that haven't been encoded to HTML output (because of XSS).
In other contexts different sub-strings are dangerous, for example, if you write an user-provided URL into a link, the sub-string "javascript:" may be dangerous. The single quote character on the other hand is dangerous when interpolating strings in SQL queries, but perfectly safe if it is a part of a name submitted from a form or read from a database field.
The bottom line is: you can't filter random input for dangerous characters, because any character may be dangerous under the right circumstances. You should encode at the point where some specific characters may become dangerous because they cross into a different sub-language where they have special meaning. When you write a string to HTML, you should encode characters that have special meaning in HTML, using Server.HtmlEncode. If you pass a string to a dynamic SQL statement, you should encode different characters (or better, let the framework do it for you by using prepared statements or the like)..
When you are sure you HTML-encode everywhere you pass strings to HTML, then set ValidateRequest="false" in the <%@ Page ... %> directive in your .aspx file(s).
In .NET 4 you may need to do a little more. Sometimes it's necessary to also add <httpRuntime requestValidationMode="2.0" /> to web.config (reference).
From the readme word doc for RC1 (not indexed by google)
ASP.NET Compiler Post-Build Step
Currently, errors within a view file are not detected until run time. To let you detect these errors at compile time, ASP.NET MVC projects now include an MvcBuildViews property, which is disabled by default. To enable this property, open the project file and set the MvcBuildViews property to true, as shown in the following example:
<Project ToolsVersion="3.5" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
<PropertyGroup>
<MvcBuildViews>true</MvcBuildViews>
</PropertyGroup>
Note Enabling this feature adds some overhead to the build time.
You can update projects that were created with previous releases of MVC to include build-time validation of views by performing the following steps:
- Open the project file in a text editor.
- Add the following element under the top-most
<PropertyGroup> element:
<MvcBuildViews>true</MvcBuildViews>
- At the end of the project file, uncomment the
<Target Name="AfterBuild"> element and modify it to match the following:
<Target Name="AfterBuild" Condition="'$(MvcBuildViews)'=='true'">
<AspNetCompiler VirtualPath="temp" PhysicalPath="$(ProjectDir)\..\$(ProjectName)" />
</Target>
Best Answer
Simply put, no.
Silverlight and silverlight on the desktop are more like winforms/wpf applications that just happen to run on the web. They're stateful and act very differently from a web site. Silverlight apps can only be run on machines that allow silverlight to run. In a business network setup they may have group policies setup so that silverlight cannot be installed. Then you've got a problem.
ASP.NET MVC however is a stateless type of design where pretty much anyone with a web browser can get to regardless of platform. You have much more freedom with your site using ASP.NET MVC because you don't have a dependency on the end-user having any sort of runtime installed.
I think each has their place and it's pretty much obvious. Silverlight is great for creating a rich experience where applicable. I doubt you'll see too much silverlight popping up replacing web sites.