How to Track Queries on a Linq-to-sql DataContext
How to Track Queries on a Linq-to-sql DataContext
Question
In the herding code podcast 14 someone mentions that stackoverflow displayed the queries that were executed during a request at the bottom of the page.
It sounds like an excellent idea to me. Every time a page loads I want to know what sql statements are executed and also a count of the total number of DB round trips. Does anyone have a neat solution to this problem?
What do you think is an acceptable number of queries? I was thinking that during development I might have my application throw an exception if more than 30 queries are required to render a page.
EDIT: I think I must not have explained my question clearly. During a HTTP request a web application might execute a dozen or more sql statements. I want to have those statements appended to the bottom of the page, along with a count of the number of statements.
HERE IS MY SOLUTION:
I created a TextWriter class that the DataContext can write to:
public class Logger : StreamWriter
{
public string Buffer { get; private set; }
public int QueryCounter { get; private set; }
public Logger() : base(new MemoryStream())
{}
public override void Write(string value)
{
Buffer += value + "<br/><br/>";
if (!value.StartsWith("--")) QueryCounter++;
}
public override void WriteLine(string value)
{
Buffer += value + "<br/><br/>";
if (!value.StartsWith("--")) QueryCounter++;
}
}
In the DataContext's constructor I setup the logger:
public HeraldDBDataContext()
: base(ConfigurationManager.ConnectionStrings["Herald"].ConnectionString, mappingSource)
{
Log = new Logger();
}
Finally, I use the Application_OnEndRequest
event to add the results to the bottom of the page:
protected void Application_OnEndRequest(Object sender, EventArgs e)
{
Logger logger = DataContextFactory.Context.Log as Logger;
Response.Write("Query count : " + logger.QueryCounter);
Response.Write("<br/><br/>");
Response.Write(logger.Buffer);
}
Popular Answer
If you put .ToString() to a var query variable you get the sql. You can laso use this in Debug en VS2008. Debug Visualizer
ex:
var query = from p in db.Table
select p;
MessageBox.SHow(query.ToString());
Read more… Read less…
System.IO.StreamWriter httpResponseStreamWriter =
new StreamWriter(HttpContext.Current.Response.OutputStream);
dataContext.Log = httpResponseStreamWriter;
Stick that in your page and you'll get the SQL dumped out on the page. Obviously, I'd wrap that in a little method that you can enable/disable.
I have a post on my blog that covers sending to log files, memory, the debug window or multiple writers.
From Linq in Action
Microsoft has a Query Visualizer tool that can be downloaded separetly from VS 2008. it is at http://weblogs.asp.net/scottgu/archive/2007/07/31/linq-to-sql-debug-visualizer.aspx