TabControl выкидывает исключения

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
 
namespace ClientCOM
{
    internal class ClassControlKey : Form
    {
        public void Control_Key(string tab_control, byte contr, string tab_page, byte pag, string text_Box, byte symbol, KeyPressEventArgs e)
        {
            string tc = tab_control + contr;
            string tp = tab_page + pag;
            string tb = "textBox" + text_Box;
            char number = e.KeyChar;
            if (!Char.IsDigit(number) && number != 8 && number != 44 && number != 45) // цифры, клавиша BackSpace и запятая
            {
                e.Handled = true;
            }
 
            if (char.IsNumber(e.KeyChar) || ((e.KeyChar == ',') && ((((Controls[tc] as TabControl).Controls[tp] as TabPage).Controls[tb] as TextBox).Text.IndexOf(',') == -1)))
            {
                if ((((Controls[tc] as TabControl).Controls[tp] as TabPage).Controls[tb] as TextBox).Text.IndexOf(',') > 0)
                {
                    if ((((Controls[tc] as TabControl).Controls[tp] as TabPage).Controls[tb] as TextBox).Text.IndexOf(',') < (((Controls[tc] as TabControl).Controls[tp] as TabPage).Controls[tb] as TextBox).Text.Length - symbol)
                        e.Handled = true;
                }
            }
        }
    }
}

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.IO.Ports;
using System.IO;
using System.Timers;
using System.Threading;
using System.Threading.Tasks;
using System.Text.RegularExpressions;
using System.Security.Policy;
using static System.Net.Mime.MediaTypeNames;
using Microsoft.SqlServer.Server;
 
namespace ClientCOM
{
 
    public partial class Form1 : Form
    {
ClassControlKey Control_Key = new ClassControlKey();
         public void textBoxDrive_KeyPress(object sender, KeyPressEventArgs e)
        {
            Control_Key.Control_Key("tabControl", 1, "tabPage", 1, "Drive", 1, e);
        }
    }
}

internal class ClassControlKey
{
    public void Control_Key(Form1 form1, string tab_control, byte contr, string tab_page, byte pag, string text_Box, byte symbol, KeyPressEventArgs e)
    {
        string tc = tab_control + contr;
        string tp = tab_page + pag;
        string tb = "textBox" + text_Box;
        char number = e.KeyChar;
        if (!Char.IsDigit(number) && number != 8 && number != 44 && number != 45) // цифры, клавиша BackSpace и запятая
        {
            e.Handled = true;
        }
 
        if (char.IsNumber(e.KeyChar) || ((e.KeyChar == ',') && ((((form1.Controls[tc] as TabControl).Controls[tp] as TabPage).Controls[tb] as TextBox).Text.IndexOf(',') == -1)))
        {
            if ((((form1.Controls[tc] as TabControl).Controls[tp] as TabPage).Controls[tb] as TextBox).Text.IndexOf(',') > 0)
            {
                if ((((form1.Controls[tc] as TabControl).Controls[tp] as TabPage).Controls[tb] as TextBox).Text.IndexOf(',') < (((form1.Controls[tc] as TabControl).Controls[tp] as TabPage).Controls[tb] as TextBox).Text.Length - symbol)
                    e.Handled = true;
            }
        }
    }
}

    public partial class Form1 : Form
    {
ClassControlKey Control_Key = new ClassControlKey();
         public void textBoxDrive_KeyPress(object sender, KeyPressEventArgs e)
        {
            Control_Key.Control_Key(this, "tabControl", 1, "tabPage", 1, "Drive", 1, e);
        }
    }

internal class ClassControlKey
{
    public void Control_Key(TextBox textBoxDrive, KeyPressEventArgs e, byte symbol)
    {
        char number = e.KeyChar;
        if (!Char.IsDigit(number) && number != 8 && number != 44 && number != 45) // цифры, клавиша BackSpace и запятая
        {
            e.Handled = true;
        }
 
        if (char.IsNumber(e.KeyChar) || ((e.KeyChar == ',') && textBoxDrive.Text.IndexOf(',') == -1))
        {
            if (textBoxDrive.Text.IndexOf(',') > 0)
            {
                if (textBoxDrive.Text.IndexOf(',') < (textBoxDrive.Text.Length - symbol))
                    e.Handled = true;
            }
        }
    }
}

public partial class Form1 : Form
{
    ClassControlKey Control_Key = new ClassControlKey();
    
    public void textBoxDrive_KeyPress(object sender, KeyPressEventArgs e)
    {
        Control_Key.Control_Key((TextBox)sender, e, 1);
    }
}