How can I access value of a variable from one method to another method in C# ?

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C#

image-processing

I have an GUI functioning code, in which I have two methods (for button1 and button2).
I want to access 'h' and 'w' variable values from button1 method to button2 method.

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 First
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            OpenFileDialog dlg = new OpenFileDialog();
            dlg.Title = "Select an Image";
            dlg.Filter = "jpg files (*.jpg)|*.jpg";
            if (DialogResult.OK == dlg.ShowDialog())
            {
                this.pictureBox1.Image = new Bitmap(dlg.FileName);
                // pictureBox1.SizeMode = PictureBoxSizeMode.StretchImage;
                Bitmap img = new Bitmap(dlg.FileName);
                int w = img.Width;
                int h = img.Height;
                pictureBox1.Height = h;
                pictureBox1.Width = w;
                textBox1.Text = dlg.FileName;

                            }
         }

        private void button2_Click(object sender, EventArgs e)
        {
        MessageBox.Show("Height is- "+   h.ToString() +"      
        Width is- " +  w.ToString(),"Height & Width");


        }
    }
}

That is nothing but globalizing the variables. But I am unable to do that.Please help me in this context.
Thank you in advance.

What I have tried:

I have tried by declaring variables in starting of program in 'public int h,w;' way.