textbox 控制输入整数，小数

   /// <summary>
        /// keypress事件控制输入
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void decimal_KeyPress(object sender, KeyPressEventArgs e)
        {
            if ((e.KeyChar >= '0' && e.KeyChar <= '9') || e.KeyChar == '.' ||
                e.KeyChar == (char)Keys.Back || e.KeyChar == (char)Keys.Delete)
            {
                int precision = 3;
                int scale = 0;
                TextBox textBox = sender as TextBox;
                if ((e.KeyChar >= '0' && e.KeyChar <= '9') || e.KeyChar == '.')
                {
                    if (scale == 0 && e.KeyChar == '.')
                    {
                        // 没有小数部的时候，小数点输入不可
                        e.Handled = true;
                    }
                    else if (textBox.Text.Contains(".") && e.KeyChar == '.')
                    {
                        // 已经输入'.'的时候，'.'输入不可
                        e.Handled = true;
                    }
                    else
                    {
                        // 除开上面的情况，对整数部和小数部的位数检查
                        string newString = textBox.Text.Substring(0, textBox.SelectionStart) + e.KeyChar +
                                           textBox.Text.Substring(textBox.SelectionStart + textBox.SelectionLength);
                        if (newString.Contains("."))
                        {
                            // 有小数点的时候
                            string[] splits = newString.Split('.');
                            if (splits.Length > 1)
                            {
                                if (splits[0].Length > precision)
                                {
                                    e.Handled = true;
                                }
                                else if (splits[1].Length > scale)
                                {
                                    e.Handled = true;
                                }
                            }
                        }
                        else
                        {
                            // 没有小数点的时候
                            if (newString.Length > precision)
                            {
                                e.Handled = true;
                            }
                        }
                    }
                }
            }
            else
            {
                // 数字以外输入的时候
                e.Handled = true;
            }
        }