Does Dispose still get called when exception is thrown inside of a using statement?

In the example below, is the connection going to close and disposed when an exception is thrown if it is within a using statement?

using (var conn = new SqlConnection("..."))
{
    conn.Open();
    // stuff happens here and exception is thrown...
}

I know this code below will make sure that it does, but I'm curious how using statement does it.

var conn;
try
{
    conn = new SqlConnection("...");
    conn.Open();
    // stuff happens here and exception is thrown...
}
// catch it or let it bubble up
finally
{
    conn.Dispose();
}

Related:

https://stackoverflow.com/questions/141204/what-is-the-proper-way-to-ensure-a-sql-connection-is-closed-when-an-exception-is

Yes, using wraps your code in a try/finally block where the finally portion will call Dispose() if it exists. It won't, however, call Close() directly as it only checks for the IDisposable interface being implemented and hence the Dispose() method.

See also:

• https://stackoverflow.com/questions/220234/intercepting-an-exception-inside-idisposable-dispose
• https://stackoverflow.com/questions/141204/what-is-the-proper-way-to-ensure-a-sql-connection-is-closed-when-an-exception-is
• https://stackoverflow.com/questions/149609/c-using-syntax
• https://stackoverflow.com/questions/317184/c-using-keyword-when-and-when-not-to-use-it
• https://stackoverflow.com/questions/278902/using-statement-vs-try-finally
• https://stackoverflow.com/questions/212198/what-is-the-c-using-block-and-why-should-i-use-it
• https://stackoverflow.com/questions/513672/disposable-using-pattern
• https://stackoverflow.com/questions/376068/does-end-using-close-an-open-sql-connection

This is how reflector decodes the IL generated by your code:

private static void Main(string[] args)
{
SqlConnection conn = new SqlConnection("...");
try
{
conn.Open();
DoStuff();
}
finally
{
if (conn != null)
{
conn.Dispose();
}
}
}

So the answer is yes, it will close the connection if

DoStuff()

throws an exception.

Dispose() doesn't get called in this code.

class Program {
	static void Main(string[] args) {
		using (SomeClass sc = new SomeClass())
		{
			string str = sc.DoSomething();
			sc.BlowUp();
		}
	}
}

public class SomeClass : IDisposable {
	private System.IO.StreamWriter wtr = null;

	public SomeClass() {
		string path = System.IO.Path.GetTempFileName();
		this.wtr = new System.IO.StreamWriter(path);
		this.wtr.WriteLine("SomeClass()");
	}

	public void BlowUp() {
		this.wtr.WriteLine("BlowUp()");
		throw new Exception("An exception was thrown.");
	}

	public string DoSomething() {
		this.wtr.WriteLine("DoSomething()");
		return "Did something.";
	}

	public void Dispose() {
		this.wtr.WriteLine("Dispose()");
		this.wtr.Dispose();
	}
}