private void availablebtn_Click(object sender, EventArgs e)
 {
     if (bidtb.Text == "")
     {
         MessageBox.Show("Enter correct book Number!");
     }
     else
     {
         String bid = bidtb.Text;
         BookIssuer bi = new BookIssuer();
         bi.checkAvailability(bid);
     }
 }
 private void button1_Click_2(object sender, EventArgs e)
 {
     if (uidtb.Text == "")
     {
         MessageBox.Show("Enter correct user ID! ");
     }
     else
     {
         String     id = uidtb.Text;
         BookIssuer bi = new BookIssuer();
         bi.checkOverdues(id);
     }
 }
 private void availablebtn_Click(object sender, EventArgs e)
 {
     if (bidtb.Text == "")
     {
         MessageBox.Show("Enter correct book Number!");
     }
     else
     {
         String     bid = bidtb.Text;
         BookIssuer bi  = new BookIssuer();
         bi.checkAvailability(bid);
     }
 }
        private void button3_Click(object sender, EventArgs e)
        {
            if (issueuid.Text == "" || issuebid.Text == "")
            {
                MessageBox.Show("Enter Correct User Number and Book ID!");
            }
            else
            {
                String uid = issueuid.Text;
                String bno = issuebid.Text;

                Detailsissue.Text = "";
                BookIssuer bi = new BookIssuer();
                bi.issueLoan(uid, bno, Detailsissue);

                uidtb.Text = "";
                bidtb.Text = "";
            }
        }
        private void button1_Click_2(object sender, EventArgs e)
        {
            if (uidtb.Text == "")
            {
                MessageBox.Show("Enter correct user ID! ");

            }
            else{
                String id = uidtb.Text;
            BookIssuer bi = new BookIssuer();
            bi.checkOverdues(id);
            }
        }
        private void button3_Click(object sender, EventArgs e)
        {
            if (issueuid.Text == "" || issuebid.Text == "")
            {
                MessageBox.Show("Enter Correct User Number and Book ID!");
            }
            else
            {
                String uid = issueuid.Text;
                String bno = issuebid.Text;

                Detailsissue.Text = "";
                BookIssuer bi = new BookIssuer();
                bi.issueLoan(uid, bno, Detailsissue);

                uidtb.Text = "";
                bidtb.Text = "";
            }
        }