Using cac thu vien Assembly inside 1 namespace va` outside 1 namespace co' gi khac' nhau ?

[it be meo]

Hi all. I'm a new amateur in programming. E doc woai` ma` hok hieu 2 cai code snippet nhu thia' nay.

First:

namespace ABC
{
using System;
using System.Collections;
using System.Text;
using System.Web.UI.WebControls;
using System.Xml;
using System.Globalization;

public class CheckQuery
{
public CheckQuery()
{

}
public string SomeMethod(string a, string b, string c, string d)
{
do something.........
}

}

}

Second:

using System;
using System.Collections;
using System.Text;
using System.Web.UI.WebControls;
using System.Xml;
using System.Globalization;
namespace ABC
{
public class CheckQuery
{
public CheckQuery()
{

}
public string SomeMethod(string a, string b, string c, string d)
{
do something.........
}

}

}

Do' ly' do tai sao, e thay' co mot so' coder nguoi ta lam` nhu vay, voi lai e thay no' cung binh` thuong` ma`. Hok biet e co' nghi~ du'ng ko. Ma` tai sao lu'c thi khai bao' using ben inside 1 namespace luc' thi` nguoc lai ???Cac' pa'c nao` cao tay chi? giup' e voi' ? E xin thanks ca'c pa'c rat nhiu`. 2 cai' snippet code tren chi la` tuong trung thoi cac' pa'c a. Ca'i chi'nh la` e van chua hieu ra problem ? Mong cac' Pa'c chi? giu'p a.