C # textbox receiving digital decimal point

public static void Key_Press(KeyPressEventArgs e, TextBox txt)
        {
            //if (e.KeyChar != 8 && !char.IsDigit(e.KeyChar))
            //{
            //    e.Handled = true;
            //}
            if (((int)e.KeyChar < 48 || (int)e.KeyChar > 57) && (int)e.KeyChar != 8 && (int)e.KeyChar != 46)

                e.Handled = true;


            //小数点的处理。

            if (e.KeyChar == 46 )                            // decimal 
            {
                 IF (txt.Text.Length == 0 ) 
                    e.Handled = to true ;    // decimal point is not in the first place 
                the else 
                { 
                    a float F;
                     a float oldf;
                     BOOL B1 = to false , B2 = to false ; 
                    B1 = a float .TryParse (txt.Text, OUT oldf); 
                    B2 = a float.TryParse(txt.Text + e.KeyChar.ToString(), out f);
                    if (b2 == false)
                    {
                        if (b1 == true)
                            e.Handled = true;
                        else
                            e.Handled = false;
                    }
                }
            }
        }