private void btnSend_Click(object sender, EventArgs e)
 {
     if ((textBox1.Text != "") && (textBox2.Text != "") && (textBox3.Text != "") && (txtMail.Text != "") && (maskedTextBox1.Text != "") && (textBox6.Text != "") && (comboBox1.Text != ""))
     {
         if (txtMail.Text.Contains("@") && txtMail.Text.Contains(".") && txtMail.Text.Length > 3)
         {
             MessageBox.Show("Thank you for registration!!!", "Success", MessageBoxButtons.OK, MessageBoxIcon.Information);
             this.Hide();
             Login_Form f = new Login_Form();
             f.Show();
         }
         else
         {
             MessageBox.Show("Your email is incorrect", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
         }
     }
     else
     {
         MessageBox.Show("Please fill all the fields", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
     }
 }
        private void Registration_FormClosing(object sender, FormClosingEventArgs e)
        {
            Login_Form f = new Login_Form();

            f.Show();
        }