If you ARE using Add -> Class OR Add -> New Item and then selecting Class, and you're still only getting an empty code file, then your default "class" template is missing or messed up. If you are using Add -> Code OR Add -> New Item and selecting Code, the "Code" template is simply an empty ".cs" file, and will be given to you empty as such.
In C# Express, this file should be located at "C:\Program Files\Microsoft Visual Studio 9.0\Common7\IDE\VCSExpress\ItemTemplates\1033\". The template for the full (paid) version of Visual Studio will be the exact same file, only the folder location will differ. The file should be a standard zip file named "Class.zip". This zip file should contain two files, as follows:
First file should be named "Class.cs" and contain:
using System;
using System.Collections.Generic;
$if$ ($targetframeworkversion$ == 3.5)using System.Linq;
$endif$using System.Text;
namespace $rootnamespace$
{
class $safeitemrootname$
{
}
}
Second file should be named "Class.vstemplate" and contain:
<?xml version="1.0" encoding="utf-8"?>
<VSTemplate Version="3.0.0" Type="Item" xmlns="http://schemas.microsoft.com/developer/vstemplate/2005">
<TemplateData>
<Name Package="{FAE04EC1-301F-11d3-BF4B-00C04F79EFBC}" ID="2245" />
<Description Package="{FAE04EC1-301F-11d3-BF4B-00C04F79EFBC}" ID="2262" />
<Icon Package="{FAE04EC1-301F-11d3-BF4B-00C04F79EFBC}" ID="4515" />
<TemplateID>Microsoft.CSharp.Class</TemplateID>
<ProjectType>CSharp</ProjectType>
<RequiredFrameworkVersion>2.0</RequiredFrameworkVersion>
<NumberOfParentCategoriesToRollUp>1</NumberOfParentCategoriesToRollUp>
<DefaultName>Class.cs</DefaultName>
</TemplateData>
<TemplateContent>
<References>
<Reference>
<Assembly>System</Assembly>
</Reference>
<Reference>
<Assembly>System.Data</Assembly>
</Reference>
<Reference>
<Assembly>System.Xml</Assembly>
</Reference>
</References>
<ProjectItem ReplaceParameters="true">Class.cs</ProjectItem>
</TemplateContent>
</VSTemplate>
If you put all of this in place, and you still get a blank code file, consider reinstalling Visual Studio.