Forms_01

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Threading;
using System.IO;

namespace FormsApp_01
{
    public partial class Student : Form
    {
        public Student()
        {
            InitializeComponent();
        }

        private void btnOK_Click(object sender, EventArgs e)
        {
            string path = "D:\\Skola\\NOP\\Forms\\Ucenik.txt";

            if (!string.IsNullOrEmpty(textBox1.Text) && !string.IsNullOrEmpty(textBox2.Text) && !string.IsNullOrEmpty(comboBox1.Text))
            {
                using (StreamWriter sw = new StreamWriter(path))
                {
                    sw.WriteLine(textBox1.Text);
                    sw.WriteLine(textBox2.Text);
                    sw.WriteLine(comboBox1.Text);

                    textBox1.Clear();
                    textBox2.Clear();
                    comboBox1.ResetText();
                }
            }

            else
            {
                MessageBox.Show("Greška, popunite polja!");
            }
        }

        private void Student_Load(object sender, EventArgs e)
        {
            txtDateTime.Text = DateTime.Now.ToString();
        }
    }
}