SqlConnection池似乎不起作用

Question

I'm trying to optimize my code performance accessing SQL Server 2014 database and noticed that connection pooling doesn't seem to work as advertised by ADO.NET. By default it's supposed to be enabled and working out of the box (as long as same connection string is used). My experiments are showing however that opening/closing connection on SqlConnection does in fact cause Audit Login / Logout to be raised.

As per https://msdn.microsoft.com/en-us/library/vstudio/8xx3tyca(v=vs.100).aspx this should not be the case:

Login and logout events will not be raised on the server when a connection is fetched from or returned to the connection pool. This is because the connection is not actually closed when it is returned to the connection pool.

My simple test was to create a console app, similar to the following:

var conn = new SqlConnection("Data Source=(local);Integrated Security=SSPI;Initial Catalog=icedb;");

for (int i = 0; i < 3; i++)
{
    conn.Open();    
    var cmd = conn.CreateCommand();
    cmd.CommandText = "select 1";
    cmd.ExecuteScalar();
    conn.Close();
}

Running this code yeilds results captured by Sql Profiler similar to the following. Observer the multiople login/logout events which should have not been captured if pooling was working as advertised. I've been able to reproduce this on multiple machines (Windows 8/10, .NET 4.5, Sql Server 2014 Developer Edition).

Main question: How do I get connection pooling to work.

Answer 1

If is issued then connection pooling is enabled. See What does sp_reset_connection do?

To see if an Audit Login is pooled or non-pooled in the Profiler, you need to add column to the Trace and check the Audit Login and Audit Logout events. The new column will show either "1 - Nonpooled" or "2 - Pooled". In your example only the first connection has "1 - Nonpooled", the next 2 Audit Logins have EventSubClass = "2 - Pooled".