private void buttonNotAnunymos_Click(object sender, EventArgs e)
 {
     if (radioButtonLogin.Checked == true)
     {
         user = Login(textBoxName.Text, textBoxPassword.Text);
         if (user != null)
         {
             priceCompareForm = new PriceCompareForm(user);
             priceCompareForm.ShowDialog();
             this.Close();
         }
         else
         {
             MessageBox.Show("Error!\nPlease enter valid name and password!!");
         }
     }
     else if (radioButtonResgister.Checked == true)
     {
         user = Register(textBoxName.Text, textBoxPassword.Text);
         if (user != null)
         {
             priceCompareForm = new PriceCompareForm(user);
             priceCompareForm.ShowDialog();
             this.Close();
         }
         else
         {
             MessageBox.Show("Error!\nPlease enter name and password again!\nMaybe this name is already in the system.");
         }
     }
     else
     {
         MessageBox.Show("Please select one of the radio buttons!");
     }
 }
 private void buttonAnonymous_Click(object sender, EventArgs e)
 {
     priceCompareForm = new PriceCompareForm(null);
     priceCompareForm.ShowDialog();
 }