Question

What is the difference between using finally

void ReadFile(int index)
{
    // To run this code, substitute a valid path from your local machine
    string path = @"c:\users\public\test.txt";
    System.IO.StreamReader file = new System.IO.StreamReader(path);
    char[] buffer = new char[10];
    try
    {
        file.ReadBlock(buffer, index, buffer.Length);
    }
    catch (System.IO.IOException e)
    {
        Console.WriteLine("Error reading from {0}. 
           Message = {1}", path, e.Message);
    }
    finally
    {
        if (file != null)
        {
            file.Close();
        }
    }
    // Do something with buffer...
}

and not using it?

void ReadFile(int index)
{
    // To run this code, substitute a valid path from your local machine
    string path = @"c:\users\public\test.txt";
    System.IO.StreamReader file = new System.IO.StreamReader(path);
    char[] buffer = new char[10];
    try
    {
        file.ReadBlock(buffer, index, buffer.Length);
    }
    catch (System.IO.IOException e)
    {
        Console.WriteLine("Error reading from {0}. 
            Message = {1}", path, e.Message);
    }

    if (file != null)
    {
        file.Close();
    }

    // Do something with buffer...
}

Answer 1

The former example will run file.Close() regardless of whether an exception is thrown or what exception is thrown.

The latter will only run if no exception is thrown or if a System.IO.IOException is thrown.