Whether should I use try{} or using() in C#?

Question

I'm new to C#,been a pascal lover until I found C# in Depth.In Delphi there is a try{} statement that is also implemented in C#.

However,I've seen some of you mentioning "Using(){} is better than try{}".

Here's an example:

   //This might throw an exception
   sock = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
   sock.Connect(ip, port);

   //Try statement
   try
   {
       sock = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
       sock.Connect(ip, port);
   catch
   {
   }

   //using(){}
   using(sock = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
   {
          sock.Connect(ip, port);
   }

My questions:

1. What happens if the exception occurs inside the "using" statement?

2. When should I use "using" over "try" and when "try" over "using"?

3. Whats the purpose of "using" statement?

Thanks in advance!

Answer 1

Using and try are 2 very different things, and are completely orthogonal.

If an exception occurs and is not in a try block the stack unwinds until an appropriate exception handler is found. This is regardless of the using statement.

Use using {} when you want to ensure that the object is tidied up correctly after use - in your example sock will be disposed of correctly after the using block.

For more info on the use of using seach on the web (or SO) for "IDisposable".

Answer 2

The using statement is used when you're creating (and using) a new object that implements IDisposable. The using statements will always dispose of the object even if an exception is raised within the using block.

try/catch statements usually serve a completely different purpose, but the finally block in a try/catch/finally or a try/finally sort of serves the same purpose as it gets executed unconditionally. The using statment buys you the automatic call to dispose.

I recommend David Hayden's article: C# Code Review - C# Using Statement - Try / Finally - IDisposable - Dispose() - SqlConnection - SqlCommand

MSDN article on the using statement
MSDN article on Try/Catch/Finally