Singleton 模式应该是设计模式中相当常用
种了
它能够节省宝贵 CPU 或内存资源避免不必要创建对象开销然而在多线程应用中对于那些非线程安全数据库组件传统 Singleton 将容易造成不稳定如果使用 Synclock 进行同步性能损耗可能将更大特别在并发访问高 ASP.net 应用中 前十几天和网友聊天
时候他把 ThreadwiseSingleton 发给了我我随后改写成泛型类事实上它基于 Threadslot 构建因此达到了线程隔离效果您需要传入个 Func(Of TResult) 完成
化工作如果您类中含有非托管资源并无法预见可能
时请使用个 Try...Finally... 包裹将要运行
同时感到抱歉是拖延了很久很久才发出来 Imports 
.Threading
''' <summary>
''' 个线程隔离 Singleton
''' </summary>
Public Class ThreadwiseSingletonClass ThreadwiseSingleton(Of T As IDisposable)
Private Shared _Factory As Func(Of T)
''' <summary>
''' 获取构建此例子工厂类
''' </summary>
Public Shared Property Factory
Property Factory As Func(Of T)
Get
Return _Factory
End Get
Set(ByVal value As Func(Of T))
_Factory = value
End Set
End Property
''' <summary>
''' 获得线程中唯例子
''' </summary>
Public Shared ReadOnly Property InstanceProperty Instance As T
Get
Dim threadSlot As LocalDataStoreSlot = Thread.GetNamedDataSlot(GetType(T).
)
Dim threadSlotObj As Object = Thread.GetData(threadSlot)
If threadSlotObj Is Nothing Then
'Create singleton instance
Dim ins As T = Factory.Invoke
Thread.SetData(threadSlot, ins)
Return ins
Else
Return DirectCast(threadSlotObj, T)
End If
End Get
End Property
''' <summary>
''' 私有构造
''' </summary>
Private Sub NewSub New
End Sub
''' <summary>
''' 释放此 Singleton 例子使用资源请不要直接
Instance.Dispose
''' </summary>
Public Shared Sub DisposeSub Dispose
Instance.Dispose
'放空槽
Dim threadSlot As LocalDataStoreSlot = Thread.GetNamedDataSlot(GetType(T).)
Thread.SetData(threadSlot, Nothing)
End Sub
End Class
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