You can scope your extensions in our out eg

namespace Sandbox.ExtensionMethods
{
    class Class1
    {
    }
}

namespace Sandbox.ExtensionMethods.ns2
{
    static class Extension
    {
        public static void Extend2(this Class1 item)
        {
        }
    }
}

namespace Sandbox.ExtensionMethods.ns1
{
    static class Extension
    {
        public static void Extend1(this Class1 item)
        {
        }
    }
}

now putting a using for the namespace to the corresponding extension it will be scoped in

eg

using Sandbox.ExtensionMethods.ns2;

            Class1 item = new Class1();
            item.Extend2();

Or


using Sandbox.ExtensionMethods.ns1;

            Class1 item = new Class1();
            item.Extend1();

not sure where you'd use it tho, Smiley Ant