When are C# “using” statements most useful?

Question

So a using statement automatically calls the dispose method on the object that is being \"used\", when the using block is exited, right?

But when is this necessary/benef

Answer 1

I like to use them like this:

    static public void AddSampleData(String name)
    {
        String CreateScript = GetScript(String.Format("SampleData_{0}", name));
        using (IDbConnection MyConnection = GetConnection())
        {
            MyConnection.Open();
            IDbCommand MyCommand = MyConnection.CreateCommand();
            foreach (String SqlScriptLine in CreateScript.Split(';'))
            {
                String CleanedString = SqlScriptLine.Replace(";", "").Trim();
                if (CleanedString.Length == 0)
                    continue;

                MyCommand.CommandText = CleanedString;
                int Result = MyCommand.ExecuteNonQuery();
            }
        }
    }

They work great for cases where you don't want to put error checking code only cleans up and passes the error on down. The alternative method would look like this:

    static public void AddSampleData(String name)
    {
        String CreateScript = GetScript(String.Format("SampleData_{0}", name));

        IDbConnection MyConnection = null;
        try
        {
            IDbConnection MyConnection = GetConnection();
            MyConnection.Open();
            IDbCommand MyCommand = MyConnection.CreateCommand();
            foreach (String SqlScriptLine in CreateScript.Split(';'))
            {
                String CleanedString = SqlScriptLine.Replace(";", "").Trim();
                if (CleanedString.Length == 0)
                    continue;

                MyCommand.CommandText = CleanedString;
                int Result = MyCommand.ExecuteNonQuery();
            }
        }
        finally
        {
            if (MyConnection != null
                && MyConnection.State == ConnectionState.Open)
                MyConnection.Close();
        }
    }

And frankly, which method is easier to read? Same thing with forms:

    public void ChangeConfig()
    {
        using (ConfigForm MyForm = new ConfigForm())
        {
            DialogResult ConfigResult = MyForm.ShowDialog();
            if (ConfigResult == DialogResult.OK)
                SaveConfig();
        }

        ConfigForm MyForm = new ConfigForm();
        DialogResult ConfigResult = MyForm.ShowDialog();
        MyForm.Dispose();
        if (ConfigResult == DialogResult.OK)
            SaveConfig();
    }