Why use finally in C#?

Question

The code inside a finally block will get executed regardless of whether or not there is an exception. This comes in very handy when it comes to certain housekeeping functions you need to always run like closing connections.

Now, I'm guessing your question is why you should do this:

try
{
    doSomething();
}
catch
{
    catchSomething();
}
finally
{
    alwaysDoThis();
}

When you can do this:

try
{
    doSomething();
}
catch
{
    catchSomething();
}

alwaysDoThis();

The answer is that a lot of times the code inside your catch statement will either rethrow an exception or break out of the current function. With the latter code, the "alwaysDoThis();" call won't execute if the code inside the catch statement issues a return or throws a new exception.

Most advantages of using try-finally have already been pointed out, but I thought I'd add this one:

try
{
    // Code here that might throw an exception...

    if (arbitraryCondition)
    {
        return true;
    }

    // Code here that might throw an exception...
}
finally
{
    // Code here gets executed regardless of whether "return true;" was called within the try block (i.e. regardless of the value of arbitraryCondition).
}

This behaviour makes it very useful in various situations, particularly when you need to perform cleanup (dispose resources), though a using block is often better in this case.

any time you use unmanaged code requests like stream readers, db requests, etc; and you want to catch the exception then use try catch finally and close the stream, data reader, etc. in the finally, if you don't when it errors the connection doesn't get closed, this is really bad with db requests

 SqlConnection myConn = new SqlConnection("Connectionstring");
        try
        {
            myConn.Open();
            //make na DB Request                
        }
        catch (Exception DBException)
        {
            //do somehting with exception
        }
        finally
        {
           myConn.Close();
           myConn.Dispose();
        }

if you don't want to catch the error then use

 using (SqlConnection myConn = new SqlConnection("Connectionstring"))
        {
            myConn.Open();
            //make na DB Request
            myConn.Close();
        }

and the connection object will be disposed of automatically if there is an error, but you don't capture the error

Because finally will get executed even if you do not handle an exception in a catch block.