如何在asp.net中将2个下拉列表中的值相乘并在文本框中显示结果？

Question

I have a lot of dropdown lists I am building for an insurance app. Each list has a number of options given a multiplier value. My question is how can I multiply these values from separate dropdown lists to give myself a final multiplier value in a textbox? I want to use whatever value is picked from each dropdown list.

The lists are formatted as follows

<asp:DropDownList id="points" runat="server">
     <asp:ListItem Value="1.00">0</asp:ListItem>
     <asp:ListItem Value="1.05">1</asp:ListItem>
     <asp:ListItem Value="1.10">2</asp:ListItem>
     <asp:ListItem Value="1.18">3</asp:ListItem>
     <asp:ListItem Value="1.25">4</asp:ListItem>
     <asp:ListItem Value="1.32">5</asp:ListItem>
     <asp:ListItem Value="1.40">6</asp:ListItem>
     <asp:ListItem Value="1.47">7</asp:ListItem>
     <asp:ListItem Value="1.55">8</asp:ListItem>
     <asp:ListItem Value="1.62">9</asp:ListItem>
     <asp:ListItem Value="1.70">10</asp:ListItem>
     <asp:ListItem Value="1.77">11</asp:ListItem>
</asp:DropDownList>
<asp:DropDownList id="OtherPolicy" runat="server">
     <asp:ListItem value="1.20">Yes</asp:ListItem>
     <asp:ListItem value="1.00">No</asp:ListItem>
</asp:DropDownList>

I have only been coding for about 2 weeks so hopefully somebody can point me in the right direction. I have not found anything similar in the search here. Thanks guys!

Answer 1

It's important to remember that the values that are going to be stored within your DropDownLists will be strings, so the first step will be converting them to numerical values, which can be done in many ways, but for example purposes, you can use the Convert.ToDecimal() method :

// Convert your Points to a decimal
var pointsValue = Convert.ToDecimal(points.SelectedValue);

// Then convert your selection from your other DropDownList
var policyValue = Convert.ToDecimal(OtherPolicy.SelectedValue);

// Now that you have both of these, you can multiply them to retrieve your result
var result = pointsValue * policyValue;

// Store your result in another TextBox
YourResultTextBox.Text = result.ToString();

If you have more DropDownLists or other elements that would need to be part of this calculation, you would just need to ensure that you parse each of their values and then include them in your calculation.