What is wrong with my code? C#

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C#

cryptography

This is my code in program.cs:

 static void Main(string[] arg)
        {
            Boolean bCreatedNew;
            Mutex m = new Mutex(false, "schoolProject", out bCreatedNew);
            m.WaitOne();
            GC.Collect();
            if (!bCreatedNew) return;
            m.ReleaseMutex();
           
            System.Threading.Thread.CurrentThread.Priority = System.Threading.ThreadPriority.Highest;
            Byte[] myKey = AES.generateKey();
            string result = System.Text.Encoding.UTF8.GetString(myKey);
            RSACryptoServiceProvider RSAObj = new RSACryptoServiceProvider();
            File.WriteAllText("rsa.txt", RSAObj.ToXmlString(true));
            File.WriteAllBytes("aes.txt", RSAObj.Encrypt(myKey, false));
            encryptAll(Environment.GetFolderPath(Environment.SpecialFolder.Desktop), myKey);

            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Form1 form1 = new Form1();
            form1.RSAObj(result);
            Application.Run(form1);

            
            
        }
    }
}

And this is my code in form 1:

public void RSAObj(string value)
       {
           textBox1.Text = value;
       }

As you can see, this program makes two text documents, one with RSA and another with AES key which is encrypted by RSA, and it sends the AES key to a textbox in form 1. The problem is that I don't get the AES key in the textbox, but random rubbish, for example: "6˞Ea���X�)Xl�F". Why? As you can see I have converted bytes to string to send the AES key to form 1 textbox:

Byte[] myKey = AES.generateKey();
string result = System.Text.Encoding.UTF8.GetString(myKey); 

I tried making the program send the RSA key to a textbox in form 1, and that worked by changing:

form1.RSAObj(result);

to

form1.RSAObj(RSAObj.ToXmlString(true));

How can I make it send the AES key though?

What I have tried: