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 = 0;                  //记录小数点个数  
                int k = 0;                  //记录小数位数  
                int dotloc = -1;            //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 = 0; 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 >= 1)
                    {
                        if (e.KeyChar == '.')
                        {
                            if (numWeight.SelectedText.IndexOf('.') == -1)
                                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 > 2)        //the condition also can be instead of "textBox1.Text.Substring(textBox1.SelectionStart).Length-textBox1.SelectionLength>2"   
                                e.Handled = true;
                        }
                    }
                    if (k == 2)
                    {
                        if (numWeight.SelectionStart > numWeight.Text.IndexOf('.') && numWeight.SelectedText.Length == 0 && 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;
            }
        }