Many people believe that when they use a
using statement a Dispose method is always going to be called, and they are safe to clear resources there. For investigation reasons I also included Catch and Finally statements, because Using statement can be thought of as a following code:
try
{
// A code inside using statement
}finall{
// A dispose method
}
As seen in an example above using is not rethrowing an exception, or stopping it, it is just letting it go.
Let us consider a code below:
static void Main(string[] args)
{
Console.CancelKeyPress += new ConsoleCancelEventHandler(myHandler);
try
{
using (new DisposableClass())
{
while (true) {
}
}
}
catch
{
Console.WriteLine("Catch");
}
finally {
Console.WriteLine("Finally");
}
}
protected static void myHandler(object sender, ConsoleCancelEventArgs args)
{
Console.WriteLine("myHandler intercepted");
}
Where a DisposableClass is listed below
public class DisposableClass : IDisposable
{
public void Dispose() {
Console.WriteLine("Dispose");
}
}
Many people forget that there are other methods to interrupt an application than exceptions (i.e. forcefully aborting a thread). An example is an good old SIGINT signal, also known as Ctr+C. If application is executing a code above, and is in a while loop. And someone presses Ctr+C than Dispose method, catch, finally blocks are not going to be called. If there is a need to intercept this signal, one needs to signup for a CancelKeyPress event, just as in a code above. In other words, after pressing Ctr+C the only line that is going to be displayed is:
myHandler intercepted
A next example of not executing Using/Catch/Finally block is by running
Thread.Abort()
For majority of cases the block will be executed, but when a thread is nearly finished, and it entered a Finally block, and then someone calls Thread.Abort(), then Finally block is not going to be executed.
