VB.NET 中的单例模式

老骥伏枥~2026-01-29 20:15

一、前言

单例模式保证一个类在整个程序运行期间，只有一个实例，并提供一个全局访问点。

单例模式的核心要点：构造函数私有化、内部持有唯一实例、对外提供统一访问入口

二、基础的单例实现

非线程安全

vbnet 复制代码

Public Class Singleton

    Private Shared _instance As Singleton

    Private Sub New()
    End Sub

    Public Shared Function Instance() As Singleton
        If _instance Is Nothing Then
            _instance = New Singleton()
        End If
        Return _instance
    End Function

End Class

三、线程安全的单例

使用 SyncLock

vbnet 复制代码

Public Class Singleton

    Private Shared _instance As Singleton
    Private Shared ReadOnly _lock As New Object()

    Private Sub New()
    End Sub

    Public Shared ReadOnly Property Instance As Singleton
        Get
            SyncLock _lock
                If _instance Is Nothing Then
                    _instance = New Singleton()
                End If
                Return _instance
            End SyncLock
        End Get
    End Property

End Class

双重检查锁

vbnet 复制代码

Public Class Singleton

    Private Shared _instance As Singleton
    Private Shared ReadOnly _lock As New Object()

    Private Sub New()
    End Sub

    Public Shared ReadOnly Property Instance As Singleton
        Get
            If _instance Is Nothing Then
                SyncLock _lock
                    If _instance Is Nothing Then
                        _instance = New Singleton()
                    End If
                End SyncLock
            End If
            Return _instance
        End Get
    End Property

End Class

Shared 只读实例、最简洁安全的写法

vbnet 复制代码

Public Class Singleton

    Public Shared ReadOnly Instance As New Singleton()

    Private Sub New()
    End Sub

End Class