Debugging Entity Framework SQL statements

Question

I am having a weird pattern of response time when using the Entity Framework for SQL communication.

This is from my web host:

This is from my local server:

It's the increase in response time I am worried about. I have narrowed the problem down to one single line in code Nop.Data > EfRepository.cs > public void Insert(T entity) > _entities.Add(entity); Yes I know this very specific for the NopCommerce, but the point is really that I am looking her for help on how to debug this.

Are there some events I can catch that display the SQL being executed? Or what other things can I do to find out more what is actually happening in the Entity Framework in that above command.

Answer 1

For debugging EF queries, the easiest thing is to cast the query to ObjectQuery and use ToTraceString:

var query = myContext.MyTable
    .Where(r => r.Id == searchId)
    .Select(r => r);

Console.WriteLine(((ObjectQuery)query).ToTraceString());

This will show the underlying SQL for the query, and you can run the queries manually to debug why they are slow. Here is the MSDN link:

http://msdn.microsoft.com/en-us/library/system.data.objects.objectquery.totracestring.aspx

If you're trying to get the SQL which is run when you call SaveChanges() on your context, it's not as easy. You could take a look at EFTracingProvider:

http://blogs.msdn.com/b/jkowalski/archive/2009/06/11/tracing-and-caching-in-entity-framework-available-on-msdn-code-gallery.aspx

Or, assuming you use SQL Server, you can go directly to SQL Profiler and capture the T-SQL statements (this is my preferred approach).

Answer 2

In EF6, you can also do this in the constructor of your dbcontext

Example

public BookServiceContext() : base("name=BookServiceContext")
{
    // New code:
    this.Database.Log = s => System.Diagnostics.Debug.WriteLine(s);
}

This will log to the console every SQL query EF generates. See this article for more information http://blog.oneunicorn.com/2013/05/08/ef6-sql-logging-part-1-simple-logging/