How can I add this message box to this code?

MessageBox.Show("Invalid input format. Please check all entries");

Ilget the income entered in the testbex decimal income = Convert.ToDecimal(txtIncome.Text); I/declare a variable for the tax decimal tax = Om; Ilgets tax value by calling the Calculate Tax method. tax = Calculate Tax(income); I/display tax txtTax.Text = tax.ToString(); } l/private method named Calculate Tax that receives the income amount and returns the tax amount private decimal Calculate Tax(decimal income) { //declare a variable for the tax decimal tax = Om; l/calculate the tax owed based on income if (income 9225 && income 37450 && income 90750 && income 189300 && income 411500 && income 413200) tax = 119996.25m + (int)(income - 413200) * .396m); //return the calculated tax amount return tax; } private void btnExit.Click(object sender, EventArgs e) { this.Close(); //close the form on click on Exit } Ilget the income entered in the testbex decimal income = Convert.ToDecimal(txtIncome.Text); I/declare a variable for the tax decimal tax = Om; Ilgets tax value by calling the Calculate Tax method. tax = Calculate Tax(income); I/display tax txtTax.Text = tax.ToString(); } l/private method named Calculate Tax that receives the income amount and returns the tax amount private decimal Calculate Tax(decimal income) { //declare a variable for the tax decimal tax = Om; l/calculate the tax owed based on income if (income 9225 && income 37450 && income 90750 && income 189300 && income 411500 && income 413200) tax = 119996.25m + (int)(income - 413200) * .396m); //return the calculated tax amount return tax; } private void btnExit.Click(object sender, EventArgs e) { this.Close(); //close the form on click on Exit }