winfrom 限制文本框小数点后两位

 private void numWeight_KeyPress(object sender, KeyPressEventArgs e)
        {
 
            if (char.IsNumber(e.KeyChar) || e.KeyChar == '.' || e.KeyChar == (char)Keys.Back || e.KeyChar == (char)Keys.Delete)
            {
                e.Handled = false;          //让操作生效
                int j = ;                  //记录小数点个数
                int k = ;                  //记录小数位数
                int dotloc = -;            //记录小数点位置
                bool flag = false;          //如果有小数点就让flag值为true
                for (int i = ; i < numWeight.Text.Length; i++)
                {
                    if (numWeight.Text[i] == '.')
                    {
                        j++;
                        flag = true;
                        dotloc = i;
                    }
                    if (flag)
                    {
                        if (char.IsNumber(numWeight.Text[i]) && e.KeyChar != (char)Keys.Back && e.KeyChar != (char)Keys.Delete)
                        {
                            k++;
                        }
                    }
                    if (j >= )
                    {
                        if (e.KeyChar == '.')
                        {
                            if (numWeight.SelectedText.IndexOf('.') == -)
                                e.Handled = true;//输入“.”，选取部分没有“.”操作失效
                        }
                    }
                    if (!flag)                  //此处控制没有小数点时添加小数点是否满足两位小数的情况
                    {
                        if (e.KeyChar == '.')
                        {
                            if (numWeight.Text.Length - numWeight.SelectionStart - numWeight.SelectedText.Length > )        //the condition also can be instead of "textBox1.Text.Substring(textBox1.SelectionStart).Length-textBox1.SelectionLength>2"
                                e.Handled = true;
                        }
                    }
                    if (k == )
                    {
                        if (numWeight.SelectionStart > numWeight.Text.IndexOf('.') && numWeight.SelectedText.Length ==  && e.KeyChar != (char)Keys.Delete && e.KeyChar != (char)Keys.Back)      //如果已经有两位小数，光标在小数点右边，
                            e.Handled = true;
                    }
                }
            }
            else
            {
                e.Handled = true;
            }
        }