using?System;
using?System.Collections.Generic;
using?System.Linq;
using?System.Text;
using?System.Threading.Tasks;
namespace?DBImportTool.Sgile
{
????//第一種單例模式Demo
????public?class?A
????{
????????private?volatile?static?A?_instance?=?null;
????????private?static?readonly?object?lockHelper?=?new?object();
????????private?A()?{?}
????????public?static?A?CreateInstance()
????????{
????????????//?判斷如果沒有實例過，則進行實例化創建.
????????????//?瞬間觸發量不高的網站，不需要此判斷步驟.
????????????if?(_instance?==?null)
????????????{
????????????????//鎖機制.防止重復實例化.
????????????????lock?(lockHelper)
????????????????{
????????????????????if?(_instance?==?null)
????????????????????{
????????????????????????_instance?=?new?A();
????????????????????}
????????????????}
????????????}
????????????return?_instance;
????????}
????}

????//第二種單例模式Demo
????public?sealed?class?B
????{
?
????????B()?{?}
????????public?static?B?GetInstance()
????????{
????????????return?B1.b;
????????}
????????class?B1
????????{
????????????static?B1()
????????????{
????????????}
????????????internal?static?readonly?B?b?=?new?B();
????????}
????}
}

轉載于:https://www.cnblogs.com/mcqueen/p/4023768.html

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