I am having issues this code in C#

partial class Form1 : Form { double bankBal = 10000; const double INT_RATE = 0.035; private readonly object outputLabel; private void yesButton_Click(object sender, EventArgs e) { outputLabel.Text += String.Format("Bank balance is (0) "); bankBal.ToString("C"); bankBal = bankBal + bankBal * INT_RATE; } private void noButton_Click(object sender, EventArgs e) { outputLabel.Text = String.Format("Have a nice day!"); } }