How to specify ADO.NET connection timeouts of less than a second? - ado.net

Question

Connection time outs are specified in the connectionString in web.config file like this:
"Data Source=dbs;Initial Catalog=db;"+"Integrated Security=SSPI;Connection Timeout=30"
The time is in seconds. I want to specify a connection timeout in milliseconds, say 500ms. How can I do that?
Edit 1: I want to do this to create a ping method which just checks if the database is reachable or not.
Edit 2: I have been searching for some similar solutions and this answer mentioned specifying timeout in milliseconds. So I was intrigued and wanted to find out how it can be done.

Answer 1

Firstly, please make sure that you are using non-pooled connections to ensure that you are always getting a fresh connection, you can do this by adding Pooling=false to your connection string. For both of these solutions I would also recommend adding Connection Timeout=1 just to ensure that ADO.NET does not needlessly continue to open the connection after you application has given up.
For .Net 4.5 you can use the new OpenAsync method and a CancellationToken to achieve a short timeout (e.g. 500ms):
using (var tokenSource = new CancellationTokenSource())
using (var connection = new SqlConnection(connectionString))
{
tokenSource.CancelAfter(500);
await connection.OpenAsync(tokenSource.Token);
}
When this times out you should see the Task returned by OpenAsync go to the canceled state, which will result in a TaskCanceledException
For .Net 4.0 you can wrap the connection open in a Task and wait on that for the desired time:
var openTask = Task.Factory.StartNew(() =>
{
using (var connection = new SqlConnection(connectionString))
{
connection.Open();
}
});
openTask.ContinueWith(task =>
{
// Need to observe any exceptions here - perhaps you might log them?
var ignored = task.Exception;
}, TaskContinuationOptions.OnlyOnFaulted);
if (!openTask.Wait(500))
{
// Didn't complete
Console.WriteLine("Fail");
}
In this example, openTask.Wait() will return a bool that indicates if the Task completed or not. Please be aware that in .Net 4.0 you must observe all exceptions thrown inside tasks, otherwise they will cause your program to crash.
If you need examples for versions of .Net prior to 4.0 please let me know.