session - 静态属性间歇性地失去其值(value)？

Question

以下设计是否存在根本性错误，或者有人能明白为什么静态属性有时会丢失其值吗？

我有一个包含 AppConfig 类的类库项目；此类由 Webforms 项目使用。

AppConfig类的框架如下:

Public Class AppConfig
    Implements IConfigurationSectionHandler

    Private Const C_KEY1        As String = "WebConfig.Key.1"
    Private Const C_KEY2        As String = "WebConfig.Key.2"
    Private Const C_KEY1_DEFAULT_VALUE  as string = "Key1defaultVal"
    Private Const C_KEY2_DEFAULT_VALUE  as string = "Key2defaultVal"

    Private Shared m_field1 As String
    Private Shared m_field2 As String

    Public Shared ReadOnly Property ConfigValue1() As String
        Get
            ConfigValue1= m_field1
        End Get
    End Property

    Public Shared ReadOnly Property ConfigValue2() As String
        Get
            ConfigValue2 = m_field2
        End Get
    End Property


    Public Shared Sub OnApplicationStart()
        m_field1    = ReadSetting(C_KEY1, C_KEY1_DEFAULT_VALUE)
        m_field2    = ReadSetting(C_KEY2, C_KEY1_DEFAULT_VALUE)
    End Sub

    Public Overloads Shared Function ReadSetting(ByVal key As String, ByVal defaultValue As String) As String
        Try
            Dim setting As String = System.Configuration.ConfigurationManager.AppSettings(key)
            If setting Is Nothing Then
                ReadSetting = defaultValue
            Else
                ReadSetting = setting
            End If
        Catch
            ReadSetting = defaultValue
        End Try
    End Function

    Public Function Create(ByVal parent As Object, ByVal configContext As Object, ByVal section As System.Xml.XmlNode) As Object Implements System.Configuration.IConfigurationSectionHandler.Create
        Dim objSettings As NameValueCollection
        Dim objHandler As NameValueSectionHandler

        objHandler = New NameValueSectionHandler
        objSettings = CType(objHandler.Create(parent, configContext, section), NameValueCollection)

        Return 1
    End Function

End Class

静态属性在应用程序启动时从 Global.asax 的 Application_Start 事件中设置一次

Sub Application_Start(ByVal sender As Object, ByVal e As EventArgs)

    //Fires when the application is started
    AppConfig.OnApplicationStart()

End Sub

此后，每当我们想要从任何地方访问 Web.Config 中的值时，例如aspx页面代码隐藏或另一个类或引用的类，我们只需调用静态属性。

例如，

AppConfig.ConfigValue1()
AppConfig.ConfigValue2() 

这将返回存储在静态支持字段 m_field1、m_field2 中的值

问题是有时这些值是空字符串，而 Web.Config 条目显然有值。

上述设计是否存在根本性错误，或者期望静态属性在应用程序 session 的生命周期内保持其值是否合理？

Answer 1

我会添加一些调试/跟踪输出，也许可以看看发生了什么。确保也找出任何异常情况。

我还会更改属性返回以使用现代语法(我不确定它的支持程度如何)。

return defaultValue

而不是:

ReadSetting = defaultValue