来自websvc的dropdownlist中的输入字符串格式不正确

Question

I'm trying to integrate my self-created web service together with my web-application. In my websvc, i created a method like below.

public double CarTaxwithOMV(int coetax)
    { 
        double coe = coetax;

        if (coetax == 1)
        {
            coe = 1.3;
        }
        else if (coetax == 2)
        {
            coe=1.1;
        }
        else if (coetax == 3)
        {
            coe = 1;
        }
}

Then in my web-application i tried to call the values above in my web-application

int coe = Convert.ToInt32("DropDownList1.SelectedValue");

double totalcost = tc.CarTaxwithOMV(coe);

lblinfo.Text = "Your total car tax for the above information is " + totalcost + ".";

In my aspx page, i have assigned a value with my dropdownlist options.

    <asp:ListItem Value="1">COEs obtained from May 2002 to February 2004 tender exercises</asp:ListItem>
    <asp:ListItem Value="2">COEs obtained from March 2004 to February 2008 tender exercises.</asp:ListItem>
    <asp:ListItem Value="3">COEs obtained from March 2008 onwards tender exercises.</asp:ListItem>

The value i declare in both my websvc and aspx page are all in integer. However when i tried to call and obtain the value from the websvc method to my web application i got this error at the dropdownlist

Input string was not in a correct format

Does anyone have any idea how does this error come from ?

Answer 1

You are getting this error because you are trying to convert string to integer.

your line

int coe = Convert.ToInt32("DropDownList1.SelectedValue");

should be

int coe = Convert.ToInt32(DropDownList1.SelectedValue);

on a side note i would also recommend that you use int.TryParse instead of convert.ToInt32

Answer 2

You didn't return a value from CarTaxwithOMV method. And also Convert.ToInt32("DropDownList1.SelectedValue"); Should be

Convert.ToInt32(DropDownList1.SelectedValue);

You are trying to convert a string value instead of a integer..