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c#try-catchtry-catch-finally
omega
omega

Reputation: 43833

How does the try catch finally block work?

In C#, how does a try catch finally block work?

So if there is an exception, I know that it will jump to the catch block and then jump to the finally block.

But what if there is no error, the catch block wont get run, but does the finally block get run then?

Upvotes: 60

Views: 122146

Answers (6)

Mayer Spitz
Mayer Spitz

Reputation: 2525

The finally block will always execute before the method returns.

Try running the code below, you'll notice that the Console.WriteLine("executed") of within the finally statement, executes before the RunTry() has a chance to return.

static void Main(string[] args)
{
    Console.WriteLine("Hello World!");
    Console.WriteLine(RunTry());
    Console.ReadLine();
}
public static int RunTry()
{
    try
    {
        throw new Exception();
    }
    catch (Exception)
    {
        return 0; // `return` waits and executes only after the `finally` block
    }
    finally
    {
        Console.WriteLine("executed");
    }
    Console.WriteLine("will not be executed since the method already returned");
}

See the result:

Hello World!
executed
0

Upvotes: 18

Vikas Lalwani
Vikas Lalwani

Reputation: 1061

Yes, Finally will always execute.

Even if there is no catch block after try, finally block will still execute.

Basically finally can be used to release resources such as a file streams, database connections and graphics handlers without waiting for the garbage collector in the runtime to finalize the object. 

       try
        {
            int a = 10;
            int b = 0;
            int x = a / b;
        }
        catch (Exception e)
        {
            Console.WriteLine(e);
        }
        finally
        {
            Console.WriteLine("Finally block is executed");
        }
        Console.WriteLine("Some more code here");

Output:

System.DivideByZeroException: Attempted to divide by zero.

Finally block is executed

Rest of the code

Source : Exception handling in C# (With try-catch-finally block details)

Upvotes: 1

Balaji
Balaji

Reputation: 1515

        try
        {
            //Function to Perform
        }
        catch (Exception e)
        {
         //You can display what error occured in Try block, with exact technical spec (DivideByZeroException)
            throw; 
            // Displaying error through signal to Machine, 
            //throw is usefull , if you calling a method with try from derived class.. So the method will directly get the signal                
        }

        finally  //Optional
        {
            //Here You can write any code to be executed after error occured in Try block
            Console.WriteLine("Completed");
        }

Upvotes: 0

Rohan M Nabar
Rohan M Nabar

Reputation: 83

finally block always run , no matter what. just try this method

     public int TryCatchFinally(int a, int b)
    {
        try
        {
            int sum = a + b;
            if (a > b)
            {
                throw new Exception();
            }
            else
            {
                int rightreturn = 2;
                return rightreturn;
            }
        }
        catch (Exception)
        {
            int ret = 1;
            return ret;
        }
        finally
        {
            int fin = 5;
        }
    }

Upvotes: 1

James Hill
James Hill

Reputation: 61793

Yes, the finally block gets run whether there is an exception or not.

Try
    [ tryStatements ]
    [ Exit Try ]
[ Catch [ exception [ As type ] ] [ When expression ]
    [ catchStatements ]
    [ Exit Try ] ]
[ Catch ... ]
[ Finally
    [ finallyStatements ] ] --RUN ALWAYS
End Try

See: http://msdn.microsoft.com/en-us/library/fk6t46tz%28v=vs.80%29.aspx

Upvotes: 57

Sohail
Sohail

Reputation: 780

Yes the finally clause gets exeucuted if there is no exception. Taking an example

     try
        {
            int a = 10;
            int b = 20;
            int z = a + b;
        }
        catch (Exception e)
        {
            Console.WriteLine(e.Message);
        }
        finally
        {
            Console.WriteLine("Executed");
        }

So here if suppose an exception occurs also the finally gets executed.

Upvotes: 13

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