Disable close button for dynamically created form

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C#

ASP.NET

WinForms

forms

I want to disable close() button for a dynamically created form.
I able to do so by overriding

CreateParamsforms

method form forms add to project through solution explorer. But it doesn't work for forms created dynamically through a code behind. I.e. I'm not able to invoke

CreateParams

from dynamic form.

What I have tried:

below is the working solution to disable close button by overriding CreateParams method for a form add through solution explorer

public partial class Form1 : Form
    {
        #region Private Variables
        private const int CP_NOCLOSE_BUTTON = 0x200;
        #endregion
        public Form1()
        {
            InitializeComponent();
        }
        protected override CreateParams CreateParams
        {
            get
            {
                var myCp = base.CreateParams;
                myCp.ClassStyle = myCp.ClassStyle | CP_NOCLOSE_BUTTON;
                return myCp;
            }
        }
        private void Form1_Load(object sender, EventArgs e)
        {
            
        }
    }

But, for below mentioned dynamic form, How could I disable close button

public static DialogResult CustomDialogBox(string title, string _lblUserName, string _lblPassword, ref string proxyUserName, ref string proxyPassword)
        {
            Form frmProxyAuthDialog = new Form();
            frmProxyAuthDialog.FormClosing += FrmProxyAuthDialog_FormClosing;
            Label lblUserName = new Label();
            Label lblPassword = new Label();
            TextBox txtUserName = new TextBox();
            TextBox txtPassword = new TextBox();
            txtPassword.PasswordChar = '*';
            Button buttonOk = new Button();
            //Button buttonCancel = new Button();

            frmProxyAuthDialog.Text = title;
            lblUserName.Text = _lblUserName;
            lblPassword.Text = _lblPassword;

            buttonOk.Text = "OK";
            //buttonCancel.Text = "Cancel";
            buttonOk.DialogResult = DialogResult.OK;
            //buttonCancel.DialogResult = DialogResult.Cancel;

            lblUserName.SetBounds(9, 10, 372, 13);
            txtUserName.SetBounds(12, 30, 372, 20);

            lblPassword.SetBounds(9, 52, 372, 13);
            txtPassword.SetBounds(12, 68, 372, 20);
            buttonOk.SetBounds(228, 90, 75, 23);
            //buttonCancel.SetBounds(309, 72, 75, 23);

            lblUserName.AutoSize = true;
            lblPassword.AutoSize = true;

            txtUserName.Anchor = txtUserName.Anchor | AnchorStyles.Right;
            txtPassword.Anchor = txtPassword.Anchor | AnchorStyles.Right;

            buttonOk.Anchor = AnchorStyles.Bottom | AnchorStyles.Right;
            //buttonCancel.Anchor = AnchorStyles.Bottom | AnchorStyles.Right;

            frmProxyAuthDialog.ClientSize = new Size(396, 120);
            frmProxyAuthDialog.Controls.AddRange(new Control[] { lblUserName, lblPassword, txtUserName, txtPassword, buttonOk });
            frmProxyAuthDialog.ClientSize = new Size(Math.Max(300, lblUserName.Right + 10), frmProxyAuthDialog.ClientSize.Height);
            frmProxyAuthDialog.FormBorderStyle = FormBorderStyle.FixedDialog;
            frmProxyAuthDialog.StartPosition = FormStartPosition.CenterScreen;
            frmProxyAuthDialog.MinimizeBox = false;
            frmProxyAuthDialog.MaximizeBox = false;
            frmProxyAuthDialog.AcceptButton = buttonOk;
            //frmProxyAuthDialog.CancelButton = buttonCancel;

            DialogResult dialogResult = frmProxyAuthDialog.ShowDialog();
            proxyUserName = txtUserName.Text;
            proxyPassword = txtPassword.Text;
            return dialogResult;
        }

I also tried to cancel form closing on form closing event if closing reason is not userclosing. But, if form closing reason is always userclosing if close button is clicked first.