以下设计是否存在根本性错误,或者任何人都可以看到为什么静态属性有时会丢失它们的值?静态属性间歇性地失去其价值?
我有一个类库项目包含一个类AppConfig;这个类被Webforms项目使用。
的AppConfig类的骨架如下:
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
静态属性得到在应用程序启动设置一次,从在Global.asax
Sub Application_Start(ByVal sender As Object, ByVal e As EventArgs)
//Fires when the application is started
AppConfig.OnApplicationStart()
End Sub
Application_Start事件之后,每当我们想要从任何地方访问Web.Config中的值,例如aspx页面代码隐藏或其他类或引用类,我们只需调用静态属性。
例如,
AppConfig.ConfigValue1()
AppConfig.ConfigValue2()
这反过来又返回存储在静态支持字段m_field1值,m_field2
问题是有时这些值是空字符串,当明确了的Web.Config条目具有值。
上述设计是否存在根本性错误,还是期望静态属性能够保持它们在应用程序会话期间的价值是合理的?