Practical .NET

Find Out What Your Entity Framework Query Is Really Doing

You can turn on logging for your Entity Framework code with a single line. Configuring it to write to a file takes only a little bit more effort.

Assuming that you're using Entity Framework 6, you already have a logging tool that can give you some insights into the SQL your queries are generating and the time they take to run. The Database property of your DbContext object has a Log property that will give you that information. To turn on logging, you just have to set the Log property to a method that will write to a log. This example sets up logging to write Entity Framework messages to to the Debug window:

Dim db As SalesOrderEntities
db = New SalesOrderEntities()
db.Database.Log = AddressOf Debug.WriteLine

In C#, you won't need the AddressOf keyword. You don't have to touch your code to make this change and you can also write your output to file by making some changes in your config file. To turn on logging to a file from your config file, just add a reference to the DatabaseLogger in the System.Data.Entity.Infrastructure.Interception namespace and point it to a file with XML, like this:

<interceptors>
  <interceptor type=
    "System.Data.Entity.Infrastructure.Interception.DatabaseLogger, EntityFramework">
    <parameters>
      <parameter value="C:\Logs\MyApplication.txt"/>
    </parameters>
  </interceptor>
</interceptors>

Here's what the output looks like (slightly edited):

Opened connection at 08-Nov-16 12:15:51 PM -05:00

SELECT TOP (1) 
  [c].[Id] AS [Id], 
  [c].[FirstName] AS [FirstName], 
  [c].[LastName] AS [LastName], 
  [c].[CustCreditStatus] AS [CustCreditStatus], 
  [c].[CreditLimit] AS [CreditLimit], 
  [c].[RenewalDate] AS [RenewalDate], 
  [c].[Valid] AS [Valid]
  FROM [dbo].[Customers] AS [c]
-- Executing at 08-Nov-16 12:15:51 PM -05:00
-- Completed in 3 ms with result: SqlDataReader
Closed connection at 08-Nov-16 12:15:51 PM -05:00

when I used the First method on one of my tables.

About the Author

Peter Vogel is a system architect and principal in PH&V Information Services. PH&V provides full-stack consulting from UX design through object modeling to database design. Peter tweets about his VSM columns with the hashtag #vogelarticles. His blog posts on user experience design can be found at http://blog.learningtree.com/tag/ui/.

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