[RESOLVED] How to access Form1 controls from another class?

Hi all c#corner forums,
I'm trying to create my class, but I couldn't succeed to work this code. When I run program, newSerial.sendData() in the Form1.Load() (this is my function which is in my own class) works perfectly, but when I clicked the button (you can see the code, I'm calling the same function) program throws "NullReferenceException" error. What is the solution?

Code:

---

namespace robitSeri
{
   
    public partial class Form1 : Form
    {
        public mySerial newSerial;

        private void Form1_Load(object sender, EventArgs e)
        {
            mySerial newSerial = new mySerial(this);
            newSerial.sendData();
 
            // THIS WORKS EXCELLENTLY..
        }
       
        private void button1_Click(object sender, EventArgs e)
        {
                newSerial.sendData();
              // THIS CODE DOES NOT WORK!!!
          }
 
     
    }

    public class mySerial // this class created by me
    {
          private Form1 frm;

        public mySerial(Form1 newFrm)
        {
          this.frm=newFrm;
        }

        public void sendData()
        {
          frm.serialPort1.Write(sth);
        }

   
    }
}

---

I am unsure as to why this cannot work, but can you use the following code instead?

Code:

---

namespace robitSeri
{

    public partial class Form1 : Form
    {
        public mySerial newSerial;

        private void Form1_Load(object sender, EventArgs e)
        {
            mySerial newSerial = new mySerial(this.serialPort1);
            newSerial.sendData();

            // THIS WORKS EXCELLENTLY..
        }

        private void button1_Click(object sender, EventArgs e)
        {
            newSerial.sendData();
            // THIS CODE DOES NOT WORK!!!
        }
    }

    public class mySerial // this class created by me
    {
        private Form1 frm;
        private System.IO.Ports.SerialPort Port;
        public mySerial(System.IO.Ports.SerialPort serialPort)
        {
            Port = serialPort;
        }

        public void sendData()
        {
            Port.Write(sth);
        }
    }
}

---

Ok, I've found my mistake. In the Form_Load method I've wrote a decleration

Code:

---

  private void Form1_Load(object sender, EventArgs e)
        {
            mySerial newSerial = new mySerial(this);
         
        }

---

but there is no need to be new decleration using mySerial (or object name). I've fixed code as below and now it's running perfectly.

private void Form1_Load(object sender, EventArgs e)
{
newSerial = new mySerial(this);

}