FxCop gives interesting advice. With it's help I've gone from a very simple and incorrect...
using System;
namespace calc

To a much more impressive and correct...
using System;
using System.Reflection;
using System.Security.Permissions;
using System.Globalization;
[assembly:CLSCompliant(true)]
[assembly: AssemblyVersionAttribute("0.9.0.0")]
[assembly: System.Runtime.InteropServices.ComVisible(false)]
[assembly: SecurityPermission(
SecurityAction.RequestMinimum, Execution = true)]
[assembly: PermissionSet(
SecurityAction.RequestOptional, Name = "Nothing")]
namespace Calc

What all this means is as follows:
[assembly:CLSCompliant(true)]
This marks the code as CLS Compliant

using System.Reflection;
[assembly: AssemblyVersionAttribute("0.9.0.0")]
Allows versioning by adding an instance of AssemblyInfo.cs. This is also seems to be where you can specify a keyfile for strong naming.

using System.Security.Permissions;
[assembly: SecurityPermission(
SecurityAction.RequestMinimum, Execution = true)]
[assembly: PermissionSet(
SecurityAction.RequestOptional, Name = "Nothing")]
Marks the code as having the minimal security permissions.

[assembly: System.Runtime.InteropServices.ComVisible(false)]
The code is not COM visible.

using System.Globalization;
Allows for some culture info to be used when converting strings to double sor vice versa. Nice to be told about this now, before I decide to sell my calculator in France. :)

And finally...
namespace Calc
The namespace identifier should use PascalCase. Tut, tut.

It's a fairly impressive start to a program, and I can understand why they keep all this out of all the simple example code you see. The other recommendation is that the assembly should have a strong name, which is definitely something I should look into.