Excetption handling Struggle

using System;
using System.Collections.Generic;
using System.ComponetModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace Calc {
    //is a basic calculator
    public partial class Form1 : Form {
        public Form1() {
            InitializeComponent();
        }

        private string AddValues(double lhs,double rhs){
            double result = lhs + rhs;
            txtExpr.Text = $"{lhs} + {rhs}";
            return result.ToString();
        }

        private String SubtractValues(double lhs,double rhs) {
            double result = lhs - rhs;
            txtExpr.Text = $"{lhs} - {rhs}"
            return result.ToString();
        }

        private string DivideValues(double lhs,double rhs) {
            double result = lhs / rhs;
            txtExpr.Text = $"{lhs} / {rhs}";
            return result.ToString();
            /*
            Getting unused local varible when I try
                double result;
                try{
                    result = lhs/ rhs;
                } catch (DivideByZeroException ex){
                //insert a messagebox here
                }
                //set Expression TextBox
                return result.ToString() // Gives unused Local varible warning
                */
        }

        private string SquareRootValues(double lhs){
            double result = Math.Sqrt(lhs);
            txtExpr.Text = $"The Square root of {lhs}";
            return result.ToString();
        }

        private string RaisePowerValues(double lhs,double rhs) {
            double result = Math.Pow(lhs,rhs);
            txtExpr.Text =$"{lhs} raised to the power of {rhs}";
            return result.ToString();
        }

        private void DoCalculate(double lhs, double rhs) {
            if (radAdd.Checked) {
                txtResult.Text = AddValues(double.Parse(txtLeft.Text), double.Parse(txtRight.Text));
            }else if (radDiv.Checked) {
                try {
                    txtResult.Text = DivideValues(double.Parse(txtLeft.Text), double.Parse(txtRight.Text));
                }catch (DivideByZeroException ex) {
                    MessageBox.Show("Cannot Divide by Zero", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                    txtResult.Text = String.Empty;
                    txtExpr.Text = String.Empty;
                }
            }else if (radMult.Checked) {
                txtResult.Text = MultiplyValues(double.Parse(txtLeft.Text), double.Parse(txtRight.Text));
            }else if (radSub.Checked) {
                txtResult.Text = SubtractValues(double.Parse(txtLeft.Text), double.Parse(txtRight.Text));
            }else if (radSqrt.Checked) {
                txtRight.Enabled = false;
                txtResult.Text = SquareRootValues(double.Parse(txtLeft.Text));
            }else if (radPow.Checked) {
                txtResult.Text = RaisePowerValues(double.Parse(txtLeft.Text), double.Parse(txtRight.Text));
            }

        }