Starting with EF6.1 you can register interceptors in the config file. Interceptors allow you to run additional logic when EF performs certain operations, such as executing database queries, opening connections, etc.
Interceptors are registered by including an interceptor element under the interceptors child section of the entityFramework section. For example, the following configuration registers the built-in DatabaseLogger interceptor that will log all database operations to the Console.
<interceptors>
<interceptor type="System.Data.Entity.Infrastructure.Interception.DatabaseLogger, EntityFramework"/>
</interceptors>Registering interceptors via the config file is especially useful when you want to add logging to an existing application to help debug an issue.DatabaseLogger supports logging to a file by supplying the file name as a constructor parameter.
<interceptors>
<interceptor type="System.Data.Entity.Infrastructure.Interception.DatabaseLogger, EntityFramework">
<parameters>
<parameter value="C:\Temp\LogOutput.txt"/>
</parameters>
</interceptor>
</interceptors>By default this will cause the log file to be overwritten with a new file each time the app starts. To instead append to the log file if it already exists use something like:
<interceptors>
<interceptor type="System.Data.Entity.Infrastructure.Interception.DatabaseLogger, EntityFramework">
<parameters>
<parameter value="C:\Temp\LogOutput.txt"/>
<parameter value="true" type="System.Boolean"/>
</parameters>
</interceptor>
</interceptors>For additional information on DatabaseLogger and registering interceptors, see the blog post EF 6.1: Turning on logging without recompiling.
原文：http://www.cnblogs.com/loui/p/entityframework.html