ValidateAll controls is empty-Reset controls-Windows application

static ErrorProvider ep = new ErrorProvider();
        public static bool ValidateEmptyTB(GroupBox gb1, GroupBox gb2)
        {

            bool ErrorinGB1 = false;
            bool ErrorinGB2 = false;

            ep.Clear();

            bool result = false;

            if (gb1 != null)
            {
                foreach (Control ctrl in gb1.Controls)
                {
                    if (ctrl is TextBox)
                    {

                        TextBox txt = (TextBox)ctrl;
                        if (txt.Text == "")
                        {
                            ErrorinGB1 = true;
                            ep.SetError(txt, "Empty TextBox");
                        }
                        else
                        {
                            ep.SetError(txt, "");

                        }

                    }
                    if (ctrl is ComboBox)
                    {
                        ComboBox cmb = (ComboBox)ctrl;

                        if (cmb.SelectedIndex == -1)
                        {
                            ErrorinGB1 = true;
                            ep.SetError(cmb, "Empty TextBox");
                        }
                        else
                        {
                            ep.SetError(cmb, "");

                        }
                    }
                }
            }


            if (gb2 != null)
            {
                foreach (Control ctrl in gb2.Controls)
                {
                    if (ctrl is TextBox)
                    {
                        TextBox txt = (TextBox)ctrl;
                        if (txt.Text == "")
                        {
                            ErrorinGB2 = true;
                            ep.SetError(txt, "Empty TextBox");
                        }
                        else
                        {
                            ep.SetError(txt, "");

                        }

                    }
                    if (ctrl is ComboBox)
                    {
                        ComboBox cmb = (ComboBox)ctrl;

                        if (cmb.SelectedIndex == -1)
                        {
                            ErrorinGB2 = true;
                            ep.SetError(cmb, "Empty TextBox");
                        }
                        else
                        {
                            ep.SetError(cmb, "");

                        }
                    }
                }
            }

            if (ErrorinGB1 == false && ErrorinGB2 == false)
            {
                ep.Dispose();
                ep.Clear();
                return result = true;
            }
            else
                return result = false;
        }


        public static void ClearForm(Control Frm)
        {
            ResetFormControlValues(Frm);
        }

        private static void ResetFormControlValues(Control parent)
        {
            foreach (Control c in parent.Controls)
            {
                if (c.Controls.Count > 0)
                {
                    ResetFormControlValues(c);
                }
                else
                {
                    switch (c.GetType().ToString())
                    {
                        case "System.Windows.Forms.TextBox":
                            ((TextBox)c).Text = "";
                            break;
                        //case "System.Windows.Forms.CheckBox":
                        //    ((CheckBox)c).Checked = false;
                        //    break;
                        case "System.Windows.Forms.ComboBox":
                            if (((ComboBox)c).Items.Count > 0)
                                ((ComboBox)c).SelectedIndex = -1;
                            break;

                    }
                }
            }

        }


        
        public static bool ValidateEmptyControl(Panel pnl)
        {
            bool result = false;

            if (pnl != null)
            {
                foreach (Control ctrl in pnl.Controls)
                {
                    if (ctrl is TextBox)
                    {

                        TextBox txt = (TextBox)ctrl;
                        if (txt.Text.Trim() != string.Empty)
                        {
                            result = true;
                        }
                    }
                    if (ctrl is ComboBox)
                    {
                        ComboBox cmb = (ComboBox)ctrl;

                        if (cmb.Text!="--Select--")
                        {
                            result = true;
                        }
                        
                    }
                    if (ctrl is RichTextBox)
                    {
                        RichTextBox rtxt = (RichTextBox)ctrl;

                        if (rtxt.Text.Trim()!=string.Empty)
                        {
                            result = true;

                        }
                    }
                    if (ctrl is DateTimePicker)
                    {
                        DateTimePicker dtp=(DateTimePicker)ctrl;

                        if(dtp.CustomFormat!=" ")
                        {
                            result=true;
                        }
                    }
                }
            }

            return result;
        }