//数字、小数点（最大到2位）、退格键、负号
        private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
        {
            if ((e.KeyChar < 48 || e.KeyChar > 57) && e.KeyChar != 8 && e.KeyChar != (char)(‘.‘) && e.KeyChar != (char)(‘-‘))
            {
                e.Handled = true;
            }
            if (e.KeyChar == (char)(‘-‘))
            {
                if ((sender as TextBox).Text != "")
                {
                    e.Handled = true;
                }
            }
            //第1位是负号时候、第2位小数点不可
            if (((TextBox)sender).Text == "-" && e.KeyChar == (char)(‘.‘))
            {
                e.Handled = true;
            }
            //负号只能1次
            if (e.KeyChar == 45 && (((TextBox)sender).SelectionStart != 0 || ((TextBox)sender).Text.IndexOf("-") >= 0))
                e.Handled = true;
            //第1位小数点不可
            if (e.KeyChar == (char)(‘.‘) && ((TextBox)sender).Text == "")
            {
                e.Handled = true;
            }
            //小数点只能1次
            if (e.KeyChar == (char)(‘.‘) && ((TextBox)sender).Text.IndexOf(‘.‘) != -1)
            {
                e.Handled = true;
            }
            //小数点（最大到2位）   
            if (e.KeyChar != ‘\b‘ && (((TextBox)sender).SelectionStart) > (((TextBox)sender).Text.LastIndexOf(‘.‘)) + 2 && ((TextBox)sender).Text.IndexOf(".") >= 0)
                e.Handled = true;
            //光标在小数点右侧时候判断  
            if (e.KeyChar != ‘\b‘ && ((TextBox)sender).SelectionStart >= (((TextBox)sender).Text.LastIndexOf(‘.‘)) && ((TextBox)sender).Text.IndexOf(".") >= 0)
            { 
                if ((((TextBox)sender).SelectionStart) == (((TextBox)sender).Text.LastIndexOf(‘.‘)) + 1)
                {
                    if ((((TextBox)sender).Text.Length).ToString() == (((TextBox)sender).Text.IndexOf(".") + 3).ToString())
                        e.Handled = true;
                }  
                if ((((TextBox)sender).SelectionStart) == (((TextBox)sender).Text.LastIndexOf(‘.‘)) + 2)
                {
                    if ((((TextBox)sender).Text.Length - 3).ToString() == ((TextBox)sender).Text.IndexOf(".").ToString()) e.Handled = true;
                }
            }
            //第1位是0，第2位必须是小数点
            if (e.KeyChar != (char)(‘.‘) && e.KeyChar != 8 && ((TextBox)sender).Text == "0")
            {
                e.Handled = true;
            }
        }