        private void button1_Click(object sender, EventArgs e)
        {
            // create students
            Student student = new Student(15.5, 19.5, 14.5);
            // show averages with numeric indexers
            label1.Text = "Created a student with the averages:\n";
            label1.Text += "\nstudent[ 0 ] = " + student[0];
            label1.Text += "\nstudent[ 1 ] = " + student[1];
            label1.Text += "\nstudent[ 2 ] = " + student[2];
            label1.Text += "\n\nSetting student[ 0 ] to 10...\n";
            student[0] = 10;
            // set an average with the string indexer
            label1.Text += "Setting student[ \"ahmad\" ] to 20...\n";
            student["ahmad"] = 20;
            // show averages with string indexers
            label1.Text += "\nNow the student has the averages:\n";
            label1.Text += "\nstudent[ \"ali\" ] = " + student["ali"];
            label1.Text += "\nstudent[ \"ahmad\" ] = " + student["ahmad"];
            label1.Text += "\nstudent[ \"reza\" ] = " + student["reza"];
        }
