| The complete list of application domain configuration settings is shown here. These settings are manipulated programmatically through public properties on the System.AppDomainSetup object. ApplicationBase PrivateBinPath DisallowApplicationBaseProbing PrivateBinPathProbe DisallowPublisherPolicy DisallowBindingRedirects ConfigurationFile LicenseFile AppDomainInitializer ConfigurationBytes ShadowCopyFiles ShadowCopyDirectories CachePath DynamicBase ApplicationName LoaderOptimization DisallowCodeDownload ActivationArguments AppDomainInitializerArguments The ConfigurationBytes "property" is actually implemented by two methods: GetConfigurationBytes and SetConfigurationBytes. Before discussing how to use AppDomainSetup, take a look at the general categories of settings you can apply to an application domain: Private assembly location settings These settings are used to specify the root directory (and the structure of its subdirectories) in which the CLR will look for assemblies considered private to a particular application domain. The settings in this category are represented by the ApplicationBase, PrivateBinPath, DisallowApplicationBaseProbing, and PrivateBinPathProbe properties on System.AppDomainSetup. Application-specific configuration settings Applications written in managed code use configuration files to store their settings. These settings can be custom settings defined by the application, or they can be settings that are known to the CLR, such as version policy statements and remote call configuration. Configuration files are associated with an application domain using either the ConfigurationFile or the ConfigurationBytes property on System.AppDomainSetup. The ability to scope an application's configuration data to the domain in which it is running is an essential part of the isolation provided by application domains. Shadow copy settings The CLR includes a feature called shadow copy that you can use to build applications that can be updated dynamically. Shadow copy works by leaving an assembly's files unlocked when they are loaded from disk. In this way, the files can be replaced and reloaded without having to shut down and restart the process. The properties used to set up the shadow copy feature are ShadowCopyFiles, ShadowCopyDirectories, CachePath, and ApplicationName. Assembly version binding settings This group of settings enables you to customize how different aspects of the version policy system apply to code running in an application domain. Specifically, you can prevent from having any effect the version policy statements made either by the application or the publisher of a shared assembly. These customizations are specified using the DisallowPublisherPolicy and DisallowBindingRedirects properties on System.AppDomainSetup. Miscellaneous settings There are a few settings that don't fit directly into the preceding categories. These settings are used to indicate whether code should be loaded into the application domain as domain neutral, to specify whether code running in the domain can dynamically download other code, and so on. The settings in this category are LicenseFile, LoaderOptimization, DynamicBase, DisallowCodeDownload, ActivationArguments, AppDomainInitializer, and AppDomainInitializerArguments.
Typically, the settings used to configure an application domain are specified when the domain is created. This is done by creating a new instance of System.AppDomainSetup, providing values for the properties you're interested in, and passing the new instance to the System.AppDomain.CreateDomain method. For example, the following code specifies the base directory in which the CLR will search for private assemblies for the new domain: using System; AppDomainSetup adSetup = new AppDomainSetup(); adSetup.ApplicationBase = @"c:\Program Files\MyApp"; AppDomain ad = AppDomain.CreateDomain("New Domain", null, adSetup);
Any time after the domain has been created, you can retrieve the current settings by obtaining an instance of AppDomainSetup using the SetupInformation property of System.AppDomain. For example, the following code prints the application root directory for the application domain running on the current thread: using System; AppDomainSetup adSetup = Thread.GetDomain().SetupInformation; Console.WriteLine("The application base directory for the current Domain is: " + adSetup.ApplicationBase);
Accessing Configuration Properties Using System.AppDomain Using AppDomain.SetupInformation is the preferred way of accessing the application domain configuration settings. However, a few of the individual settings can also be obtained directly from properties on System.AppDomain. The following table describes these properties and their AppDomainSetup equivalents. System.AppDomain Property | System.AppDomainSetup Equivalent |
|---|
BaseDirectory | ApplicationBase | RelativeSearchPath | PrivateBinPath | ShadowCopyFiles | ShadowCopyFiles |
It might seem odd that only a few of the configuration settings are exposed directly on System.AppDomain. The reason for this situation is primarily historical. The first several iterations of the AppDomain class contained just a few configurable settings, so it made perfect sense to expose them directly as properties on AppDomain. However, as time passed and the number of settings grew, it became convenient to wrap them all in the AppDomainSetup class. Unfortunately, by that time a few of the initial public betas had been released, and the CLR team decided to keep the original properties on System.AppDomain for compatibility reasons. |
As I explained earlier, you typically specify the configuration settings for an application domain when you create the domain. However, System.AppDomain exposes public methods that enable you to change the value of a small number of these settings after the domain has been created. If you use these methods to change domain settings, you must do so before any assemblies are loaded into the domain. Calling them later will have no effect. The settings that can be changed through properties on AppDomain, along with the corresponding properties on AppDomainSetup they affect, are shown in Table 6-1. Table 6-1. Application Domain Settings Exposed by System.AppDomainSystem.AppDomain Property | System.AppDomainSetup Equivalent |
|---|
AppendPrivatePath | PrivateBinPath | ClearPrivatePath | PrivateBinPath | ClearShadowCopyPath | ShadowCopyDirectories | SetCachePath | CachePath | SetDynamicBase | DynamicBase | SetShadowCopyFiles | ShadowCopyFiles | SetShadowCopyPath | ShadowCopyDirectories |
I describe how to use these methods in the following sections, where their matching AppDomainSetup property is described. Now that I've provided an overview of each of the settings, let's dig into the details of how you can use the AppDomainSetup properties to customize the application domains you create. |
