C# datetime elapsed time problem

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C#

I creating a stop watch that tracks time, and when started accumulates time then when stopped waits then when started continues on from the previous point.

My problem is when start button is clicked it picks up at the current time it does not resume at the stopped point.

What am I doing wrong?

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace WedStop
{
    public class TimerLogic
    {
    
        
        private DateTime startTime;
        private DateTime stopTime;
        private bool hasStarted = false;
        private bool hasStopped = false;

        public String ElapsedTime
        {
           
            get
            {
                if (hasStopped)
                {

                    return (DateTime.Now - stopTime).ToString();  
                }
                if (hasStarted) // good old code
                {                      
                    return (DateTime.Now - startTime).ToString();                    
                }
                return "00 HR:00 MN:00 SEC";
                }
        }
   

        public void StartClock()
        {
                if (hasStopped == false)
                { 
                   hasStarted = true; 
                   startTime = DateTime.Now; 
                }

                if (hasStopped == true)
                {
                    
                    hasStopped = true;
                }
                
                
        }

        public void StopClock() 
        {
            
            stopTime = startTime;
            hasStopped = true;
            hasStarted = false;
            
        }
    }
}


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

namespace WedStop
{
    public partial class Form1 : Form
    {
        TimerLogic stopWatch = new TimerLogic();

        public Form1()
        {
            InitializeComponent();
        }

        private void timer1_Tick(object sender, EventArgs e)
        {
            lblDisplay.Text = stopWatch.ElapsedTime;
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void btnStart_Click(object sender, EventArgs e)
        {
            
            stopWatch.StartClock();
            timer1.Start();
        }

        private void btnStop_Click(object sender, EventArgs e)
        {
            timer1.Stop();
            stopWatch.StopClock();
            
          
        }
    }
}

What I have tried:

I think the problem is in the Timer logic class with this line of code:

return (DateTime.Now - stopTime).ToString();