Question

编程的问题。

public partial class _Default : System.Web.UI.Page
{
public class car
{
private string color;
private int chelun;
public string Color
{
get
{
return color;
}
set
{
color = value;
}

}
public int Chelun
{
get
{
return chelun;
}
}
public string gg(string a, string b)
{
string c = "";

switch (a)
{
case "#red":
c += "车是红色的<br>,有" + b + "个轮子";
break;
case "#green":
c += "车是绿色的<br>,有" + b + "个轮子";
break;
case "blue":
c += "车是蓝色的<br>,有" + b + "个轮子";
break;
}
return c;
}
}

protected void Page_Load(object sender, EventArgs e)
{

}
protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
car onecar=new car();
onecar.Color = DropDownList1.SelectedIndex.ToString();
string a = onecar.Color.ToString();
string b = onecar.Chelun.ToString();
string c = onecar.gg(a, b);
Response.Write(c);
}
}

救命啊，高手。
我照这个编了，选项里都是空白的，怎么回事啊？

Answer 1

onecar.Color = DropDownList1.SelectedIndex.ToString();
值获取的时候可能包含有空格，改为onecar.Color = DropDownList1.SelectedIndex.ToString().trim();
而且
switch (a)
{
case "#red":
c += "车是红色的<br>,有" + b + "个轮子";
break;
case "#green":
c += "车是绿色的<br>,有" + b + "个轮子";
break;
case "blue":
c += "车是蓝色的<br>,有" + b + "个轮子";
break;
}
这个条件判断语句不建议把条件格式设置成这样子，条件格式不统一，应改为全部加上”#“号，或者全部不要”#“号。

Answer 2

protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
DropDownList1.Items.Add(new ListItem("请选择你车子的颜色", "0"));
DropDownList1.Items.Add(new ListItem("红色", "#red"));
DropDownList1.Items.Add(new ListItem("绿色", "#green"));
DropDownList1.Items.Add(new ListItem("蓝色", "blue"));

}
}

public class car
{
private string color;
private int chelun;
public string Color
{
get
{
return color;
}
set
{
color = value;
}

}
public int Chelun
{
get
{
return chelun;
}
}
public string gg(string a, string b)
{
string c = "";

switch (a)
{
case "#red":
c += "车是红色的<br>,有" + b + "个轮子";
break;
case "#green":
c += "车是绿色的<br>,有" + b + "个轮子";
break;
case "blue":
c += "车是蓝色的<br>,有" + b + "个轮子";
break;
}
return c;
}
}
protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
car onecar = new car();
onecar.Color = DropDownList1.SelectedValue.ToString();
string a = onecar.Color.ToString();
string b = onecar.Chelun.ToString(); //没有过值
string c = onecar.gg(a, b);
Response.Write(c);
}

Answer 3

事件不是这个事件。你写在Mousedwon事件里看看