Possible Duplicate:
Should Usings be inside or outside the namespace
Are there any technical reasons for preferring this
namespace Foo
{
using System;
using System.IO;
instead of the default
using System;
using System.IO;
namespace Foo
{
Eric Lippert explains this.
In general, they’re identical.
However,
usingstatements in the namespace can see namespaces and aliases included outside the namespace.