Assembly binding behavior can be configured at different levels based on three XML files:
- Application configuration file.
- Publisher policy file.
- Machine configuration file.
These files follow the same syntax and provide information such as binding redirects, the location of code, and binding modes for particular assemblies. Each configuration file can contain an <assemblyBinding> element that redirects the binding process. The child elements of the <assemblyBinding> element include the <dependentAssembly> element. The children of <dependentAssembly> element include the <assemblyIdentity> element, the <bindingRedirect> element, and the <codeBase> element.
Application Configuration File
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First, the common language runtime checks the application configuration file for information that overrides the version information stored in the calling assembly's manifest. The application configuration file can be deployed with an application, but is not required for application execution. Usually the retrieval of this file is almost instantaneous, but in situations where the application base is on a remote computer, such as in an Internet Explorer Web-based scenario, the configuration file must be downloaded.
For client executables, the application configuration file resides in the same directory as the application's executable and has the same base name as the executable with a .config extension. For example, the configuration file for C:\Program Files\Myapp\Myapp.exe is C:\Program Files\Myapp\Myapp.exe.config. In a browser-based scenario, the HTML file must use the <link> element to explicitly point to the configuration file.
Publisher Policy File [发布方策略文件]
Second, the runtime examines the publisher policy file, if one exists. Publisher policy files are distributed by a component publisher as a fix or update to a shared component. These files contain compatibility information issued by the publisher of the shared component that directs an assembly reference to a new version. Unlike application and machine configuration files, publisher policy files are contained in their own assembly that must be installed in the global assembly cache.
Machine Configuration File
Third, the runtime examines the machine configuration file. This file, called Machine.config, resides on the local computer in the Config subdirectory of the root directory where the runtime is installed[例如，他可能存在于C:\Windows\Microsoft.NET\Framework\v4.0.30319\Config， C:\Windows\Microsoft.NET\Framework\v2.0.50727\CONFIG]. This file can be used by administrators to specify assembly binding restrictions that are local to that computer. The settings in the machine configuration file take precedence over all other configuration settings; however, this does not mean that all configuration settings should be put in this file. The version determined by the administrator policy file is final, and cannot be overridden. Overrides specified in the Machine.config file affect all applications.