EF Profiler - 它是如何工作的？

Question

I'm trying to learn more about trying to tap into the ADO.Net / EF pipeline and how to unintuitively hook into the pipeline (to dump queries, results, etc to my log).

Everything I have seen says that there is no way to unobtrusively or without using SQL Profiler... But I know its possible as the best EF Profiler manages to do it.

Answer 1

I do not know how exactly EfProf works internally, but EF is extensible in the form of custom providers - using a custom provider you can wrap an existing provider (ie SQL Server) and inspect all traffic - this allows profiling. This article focuses on this topic: Tracing and Caching Provider Wrappers for Entity Framework - there's sample code provided.

Whenever you issue a LINQ or Entity SQL query through an ObjectContext instance, the query passes through a series of layers (see the picture below). At high level we can say that all queries and updates from ObjectContext are translated and executed through EntityConnection, which in turns talks to server-specific data provider such as SqlClient or Sql Server CE client.

Provider interface used by Entity Framework is stackable, which means it's possible to write a provider which will wrap another provider and intercept communication between Entity Framework and the original provider.

The wrapper provider gets a chance do interesting things, such as:

Examining query trees and commands before they are executed

Controlling connections, commands, transactions, data readers