protect my swf on c# form

It is not possible.
And still if you want to do so, you must have swf file in your application, and you can give EXE of it to others.

-KR

actually this little trick may work. assuming that your flash files (*.swf) are determined while you develop your application, you can add them as resource files in your project. then:

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

namespace Test_Flash
{
    public partial class Form1 : Form
    {
        List<string> tempFiles = new List<string>();

        public Form1()
        {
            InitializeComponent();
            this.FormClosed += Form1_FormClosed;
        }


        private void button1_Click(object sender, EventArgs e)
        {
            string p = Path.GetTempFileName();
            this.tempFiles.Add(p);

            // open temporay file
            using(FileStream fs = new FileStream(p, FileMode.Open))
            {
                // write your flash resource into that file.
                fs.Write(Test_Flash.Properties.Resources.harfa, 0,
                    Test_Flash.Properties.Resources.harfa.Length);
            }
            // play it
            this.axShockwaveFlash1.LoadMovie(0, p);
        }

        void Form1_FormClosed(object sender, FormClosedEventArgs e)
        {
            // remove all temporary files
            tempFiles.ForEach(f1 => File.Delete(f1));
        }
    }
}

There is no way to stop people from copying your SWF file.

1) You cannot use NTFS security to "protect" the file because the operation of reading the file for play in the player is no different than reading the file to copy it. They are exactly the same. If you remove permissions so someone cannot copy the file, they also cannot play the file in your application.

2) Adding the file to your applications resources is not going to "protect" it either. There are lots of resource editing tools out on the web that can take any resource stream in your application and write it to a file. Again, you cannot stop someone from reading the contents of the .EXE file as you would also be stopping them from running your .EXE file.