Here is a quick and dirty snippet to do just that.
To Install:
Save the code as SurroundWithBraces.snippet
into "<my documents>\Visual Studio Version\Code Snippets\Visual C#\My Code Snippets"
To use:
Select block of text.
Press Ctrl+K, Ctrl+S
Chose My Code Snippets, braces
<?xml version="1.0" encoding="utf-8" ?>
<CodeSnippets xmlns="http://schemas.microsoft.com/VisualStudio/2005/CodeSnippet">
<CodeSnippet Format="1.0.0">
<Header>
<Title>braces</Title>
<Shortcut>braces</Shortcut>
<Description>Code snippet to surround a block of code with braces</Description>
<Author>Igor Zevaka</Author>
<SnippetTypes>
<SnippetType>Expansion</SnippetType>
<SnippetType>SurroundsWith</SnippetType>
</SnippetTypes>
</Header>
<Snippet>
<Code Language="csharp">
<![CDATA[{
$selected$ $end$
}]]>
</Code>
</Snippet>
</CodeSnippet>
</CodeSnippets>