This example shows two aspects that cause a field or a property to be backed by a persistent storage:
RegistryValueAttribute is an aspect that persists a field or property into a Windows registry value.
It is useful in Windows applications that use a lot of registry settings.
AppSettingValuesAttribute retrieves the value of a field or property from the
Both aspects work in a similar way. Both aspect classes contain a field named
isFetched, which is set
true when the value has already been fetched from the storage. This is an optimization that avoids
the application from retrieving and converting the value several times. When the field or property value
is retrieved, but the
isFetched field is set to
false, then the aspect retrieves the value from
the storage, converts it from a
string to the field/property type, and sets the
RegistryValueAttribute is modifies the registry value when the value of the target field
or property is set. However, the
AppSettingsValueAttribute is not allowed to change the content
web.config file. Therefore, changing the value of the target field or property
is forbidden after the field or property value has been retrieved. However, changing the value before
the first retrieval is allowed: this is how you should set the default value of this setting.
Both aspect classes use the
[MulticastAttributeUsage(TargetMemberAttributes = MulticastAttributes.Static)]
custom attribute to specify that they can be applied only to static fields and properties.
In this example, we apply the
RegistryValueAttribute custom attribute to the
TestRegistryValues class, which
has the effect to persist all static fields of this class to registry. We're doing the same with the
AppSettingsValueAttribute custom attribute and the
If you want to persist only specific fields or properties, remove the custom attribute from the class
and add it to these specific fields or properties.
The aspect demonstrates the use of
LocationInterceptionAspect to enhance fields and properties,
[MulticastAttributeUsage] to restrict the aspects to static fields or properties.