How do I mix and generate random strings(password) in C# .NET

I am learning C# and im trying to create a random string(password) generator.. I feel like its fun because its not the simple Hello World application

I am doing this in a windows form application

I am trying to mix all the

public const string

and print it out to the TextBox2 in my project.. But the thing is I have no idea on how to actually mix them I was thinking about a for loop and check for every character.. Not really sure how I would do it..

Does anyone have any examples I could look over and try to understand how they are made? I saw one made with Linq here on SO but I couldnt really understand it because I am trying to involve check boxes

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;
using System.Runtime.InteropServices;

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

        class RandomPWDGenerator
        {
            public const string CapitilizedLetters = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
            public const string NonCapitilizedLetters = "abcdefghijklmnopqrstuvwxyz";
            public const string Numbers = "0123456789z";
            public const string SpecialCharacters = "!@#$%^*()_+";

            private static Random rnd = new Random();        
        }

        static void Main()
        {
            StringBuilder password = new StringBuilder();
            for (int i = 1; i <= 2; i++)
            {

            }
        }

        public const int WM_NCLBUTTONDOWN = 0xA1;
        public const int HT_CAPTION = 0x2;

        [DllImportAttribute("user32.dll")]
        public static extern int SendMessage(IntPtr hWnd,
                         int Msg, int wParam, int lParam);
        [DllImportAttribute("user32.dll")]
        public static extern bool ReleaseCapture();

        private void label1_Click(object sender, EventArgs e)
        {
            Application.Exit();
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void topPanel_MouseDown(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                ReleaseCapture();
                SendMessage(Handle, WM_NCLBUTTONDOWN, HT_CAPTION, 0);
            }
        }

        private void generateLbl_MouseEnter(object sender, EventArgs e)
        {
            generatePanel.BackColor = System.Drawing.ColorTranslator.FromHtml("#4d4d4d");
        }

        private void generateLbl_MouseLeave(object sender, EventArgs e)
        {
            generatePanel.BackColor = Color.Transparent;
        }

        private void generateLbl_Click(object sender, EventArgs e)
        {
        }
    }
}