Question

我正在进行一个迷你测验，我坚持使用C＃编码，检查用户从DropDownList中选择哪个ListItem。

            <li><b>What is 231 mod 55?</b>
                <asp:Label ID="lblQuestionResult2" runat="server" Font-Bold="true" Font-Size="16px" />
                <br />
                <asp:DropDownList ID="DropDownList1" runat="server" Width="55px">
                    <asp:ListItem>14</asp:ListItem>
                    <asp:ListItem>6</asp:ListItem>
                    <asp:ListItem>11</asp:ListItem>
                </asp:DropDownList>
            </li>

我所拥有的不起作用。如何检查用户选择的内容？

    if (ListItem.Equals(toString(11)))
    {
        lblQuestionResult2.ForeColor = System.Drawing.Color.Green;
        lblQuestionResult2.Text = "Correct";
    }
    else
    {
        lblQuestionResult2.ForeColor = System.Drawing.Color.Red;
        lblQuestionResult2.Text = "Incorrect";
    }

Answer 1

您的DropDownList控件已经是服务器端控件。为OnSelectedIndexChanged事件添加事件处理程序并处理它。它应该看起来像

  <asp:DropDownList ID="DropDownList1" 
       runat="server" Width="55px" AutoPostBack="true" 
       OnSelectedIndexChanged="OnComboSelectionChanged">

在后面的代码中，您可以添加像这样的处理程序

protected void OnComboSelectionChanged(object sender, EventArgs e)
{
  // Your code goes here.
  string selectedValue = DropDownList1.SelectedValue;

}

确保使用

AutoPostBack="true"

Answer 2

有两种方法可以获得它：

 //One way
 string selectedvalue = ddList.SelectedValue;

 //Second Way
 string selectedindex = ddList.SelectedItem.Text;

完整的例子：

我推出了DropDownList和Button

 <asp:DropDownList ID="ddList" runat="server">
        <asp:ListItem>14</asp:ListItem>
        <asp:ListItem>6</asp:ListItem>
        <asp:ListItem>11</asp:ListItem>
 </asp:DropDownList>

 <asp:Button ID="btnClick" runat="server" Text="Button" OnClick="btnClick_Click" />

我创建了一个方法，当用户点击按钮

时会触发该方法

protected void btnClick_Click(object sender, EventArgs e)
{

     string selectedvalue = ddList.SelectedValue;
     string selectedindex = ddList.SelectedItem.Text;
}

Answer 3

此MSDN页面应该有所帮助。看起来你需要做什么 http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.listitem.selected.aspx?cs-save-lang=1&cs-lang=csharp#code-snippet-2

Answer 4

这可能会对你有所帮助

// aspx side

 <asp:DropDownList ID="DropDownList1" runat="server" Width="55px" 
                   onselectedindexchanged="DropDownList1_SelectedIndexChanged">
                    <asp:ListItem>14</asp:ListItem>
                    <asp:ListItem>6</asp:ListItem>
                    <asp:ListItem>11</asp:ListItem>
                </asp:DropDownList>

// cs side

protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
    {
        if (DropDownList1.SelectedValue=="11")
        {
            lblQuestionResult2.ForeColor = System.Drawing.Color.Green;
            lblQuestionResult2.Text = "Correct";
        }
        else
        {
            lblQuestionResult2.ForeColor = System.Drawing.Color.Red;
            lblQuestionResult2.Text = "Incorrect";
        }
    }

Answer 5

<asp:DropDownList ID="DropDownList1" runat="server" Width="55px" 
               onselectedindexchanged="DropDownList1_SelectedIndexChanged">
                <asp:ListItem>14</asp:ListItem>
                <asp:ListItem>6</asp:ListItem>
                <asp:ListItem>11</asp:ListItem>
            </asp:DropDownList>

//背后的代码

protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
    if (DropDownList1.SelectedIndex!=0)
    {
        //your code implementation for selected value
    }
}

如何检查是否选择了ListItem？

5 个答案: